/*-
 * Copyright (c) 2005-2009 Ariff Abdullah <ariff@FreeBSD.org>
 * Portions Copyright (c) Ryan Beasley <ryan.beasley@gmail.com> - GSoC 2006
 * Copyright (c) 1999 Cameron Grant <cg@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifdef HAVE_KERNEL_OPTION_HEADERS
#include "opt_snd.h"
#endif

#include <dev/sound/pcm/sound.h>
#include <sys/ctype.h>
#include <sys/devfs.h>
#include <sys/device.h>
#include <sys/eventhandler.h>
#include <sys/lock.h>
#include <sys/sysent.h>

#include <vm/vm.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pager.h>

SND_DECLARE_FILE("$FreeBSD: head/sys/dev/sound/pcm/dsp.c 274035 2014-11-03 11:11:45Z bapt $");

static int dsp_mmap_allow_prot_exec = 0;
SYSCTL_INT(_hw_snd, OID_AUTO, compat_linux_mmap, CTLFLAG_RW,
    &dsp_mmap_allow_prot_exec, 0,
    "linux mmap compatibility (-1=force disable 0=auto 1=force enable)");

struct dsp_cdevinfo {
        struct pcm_channel *rdch, *wrch;
        struct pcm_channel *volch;
        int busy, simplex;
        TAILQ_ENTRY(dsp_cdevinfo) link;
};

#define PCM_RDCH(x)             (((struct dsp_cdevinfo *)(x)->si_drv1)->rdch)
#define PCM_WRCH(x)             (((struct dsp_cdevinfo *)(x)->si_drv1)->wrch)
#define PCM_VOLCH(x)            (((struct dsp_cdevinfo *)(x)->si_drv1)->volch)
#define PCM_SIMPLEX(x)          (((struct dsp_cdevinfo *)(x)->si_drv1)->simplex)

#define DSP_CDEVINFO_CACHESIZE  8

#define DSP_REGISTERED(x, y)    (PCM_REGISTERED(x) &&                   \
                                 (y) != NULL && (y)->si_drv1 != NULL)

#define OLDPCM_IOCTL

static d_open_t dsp_open;
static d_close_t dsp_close;
static d_read_t dsp_read;
static d_write_t dsp_write;
static d_ioctl_t dsp_ioctl;
static d_kqfilter_t dsp_kqfilter;
static d_mmap_t dsp_mmap;
static d_mmap_single_t dsp_mmap_single;

static void dsp_filter_detach(struct knote *);
static int dsp_filter_read(struct knote *, long);
static int dsp_filter_write(struct knote *, long);

DEVFS_DEFINE_CLONE_BITMAP(dsp);

struct dev_ops dsp_ops = {
        { "sound", 0, D_MPSAFE },
        .d_open =       dsp_open,
        .d_close =      dsp_close,
        .d_read =       dsp_read,
        .d_write =      dsp_write,
        .d_ioctl =      dsp_ioctl,
        .d_kqfilter =   dsp_kqfilter,
        .d_mmap =       dsp_mmap,
        .d_mmap_single = dsp_mmap_single,
};

static eventhandler_tag dsp_ehtag = NULL;
static int dsp_umax = -1;
static int dsp_cmax = -1;

static int dsp_oss_syncgroup(struct pcm_channel *wrch, struct pcm_channel *rdch, oss_syncgroup *group);
static int dsp_oss_syncstart(int sg_id);
static int dsp_oss_policy(struct pcm_channel *wrch, struct pcm_channel *rdch, int policy);
static int dsp_oss_cookedmode(struct pcm_channel *wrch, struct pcm_channel *rdch, int enabled);
static int dsp_oss_getchnorder(struct pcm_channel *wrch, struct pcm_channel *rdch, unsigned long long *map);
static int dsp_oss_setchnorder(struct pcm_channel *wrch, struct pcm_channel *rdch, unsigned long long *map);
static int dsp_oss_getchannelmask(struct pcm_channel *wrch, struct pcm_channel *rdch, int *mask);
#ifdef OSSV4_EXPERIMENT
static int dsp_oss_getlabel(struct pcm_channel *wrch, struct pcm_channel *rdch, oss_label_t *label);
static int dsp_oss_setlabel(struct pcm_channel *wrch, struct pcm_channel *rdch, oss_label_t *label);
static int dsp_oss_getsong(struct pcm_channel *wrch, struct pcm_channel *rdch, oss_longname_t *song);
static int dsp_oss_setsong(struct pcm_channel *wrch, struct pcm_channel *rdch, oss_longname_t *song);
static int dsp_oss_setname(struct pcm_channel *wrch, struct pcm_channel *rdch, oss_longname_t *name);
#endif

static struct snddev_info *
dsp_get_info(struct cdev *dev)
{
        return (devclass_get_softc(pcm_devclass, PCMUNIT(dev)));
}

static uint32_t
dsp_get_flags(struct cdev *dev)
{
        device_t bdev;

        bdev = devclass_get_device(pcm_devclass, PCMUNIT(dev));

        return ((bdev != NULL) ? pcm_getflags(bdev) : 0xffffffff);
}

static void
dsp_set_flags(struct cdev *dev, uint32_t flags)
{
        device_t bdev;

        bdev = devclass_get_device(pcm_devclass, PCMUNIT(dev));

        if (bdev != NULL)
                pcm_setflags(bdev, flags);
}

/*
 * return the channels associated with an open device instance.
 * lock channels specified.
 */
static int
getchns(struct cdev *dev, struct pcm_channel **rdch, struct pcm_channel **wrch,
    uint32_t prio)
{
        struct snddev_info *d;
        struct pcm_channel *ch;
        uint32_t flags;

        if (PCM_SIMPLEX(dev) != 0) {
                d = dsp_get_info(dev);
                if (!PCM_REGISTERED(d)) {
                        *rdch = NULL;
                        *wrch = NULL;
                        return (ENXIO);
                }
                PCM_LOCK(d);
                PCM_WAIT(d);
                PCM_ACQUIRE(d);
                /*
                 * Note: order is important -
                 *       pcm flags -> prio query flags -> wild guess
                 */
                ch = NULL;
                flags = dsp_get_flags(dev);
                if (flags & SD_F_PRIO_WR) {
                        ch = PCM_RDCH(dev);
                        PCM_RDCH(dev) = NULL;
                } else if (flags & SD_F_PRIO_RD) {
                        ch = PCM_WRCH(dev);
                        PCM_WRCH(dev) = NULL;
                } else if (prio & SD_F_PRIO_WR) {
                        ch = PCM_RDCH(dev);
                        PCM_RDCH(dev) = NULL;
                        flags |= SD_F_PRIO_WR;
                } else if (prio & SD_F_PRIO_RD) {
                        ch = PCM_WRCH(dev);
                        PCM_WRCH(dev) = NULL;
                        flags |= SD_F_PRIO_RD;
                } else if (PCM_WRCH(dev) != NULL) {
                        ch = PCM_RDCH(dev);
                        PCM_RDCH(dev) = NULL;
                        flags |= SD_F_PRIO_WR;
                } else if (PCM_RDCH(dev) != NULL) {
                        ch = PCM_WRCH(dev);
                        PCM_WRCH(dev) = NULL;
                        flags |= SD_F_PRIO_RD;
                }
                PCM_SIMPLEX(dev) = 0;
                dsp_set_flags(dev, flags);
                if (ch != NULL) {
                        CHN_LOCK(ch);
                        pcm_chnref(ch, -1);
                        pcm_chnrelease(ch);
                }
                PCM_RELEASE(d);
                PCM_UNLOCK(d);
        }

        *rdch = PCM_RDCH(dev);
        *wrch = PCM_WRCH(dev);

        if (*rdch != NULL && (prio & SD_F_PRIO_RD))
                CHN_LOCK(*rdch);
        if (*wrch != NULL && (prio & SD_F_PRIO_WR))
                CHN_LOCK(*wrch);

        return (0);
}

/* unlock specified channels */
static void
relchns(struct cdev *dev, struct pcm_channel *rdch, struct pcm_channel *wrch,
    uint32_t prio)
{
        if (wrch != NULL && (prio & SD_F_PRIO_WR))
                CHN_UNLOCK(wrch);
        if (rdch != NULL && (prio & SD_F_PRIO_RD))
                CHN_UNLOCK(rdch);
}

static void
dsp_cdevinfo_alloc(struct cdev *dev,
    struct pcm_channel *rdch, struct pcm_channel *wrch,
    struct pcm_channel *volch)
{
        struct snddev_info *d;
        struct dsp_cdevinfo *cdi;
        int simplex;

        d = dsp_get_info(dev);

        KASSERT(PCM_REGISTERED(d) && dev != NULL && dev->si_drv1 == NULL &&
            ((rdch == NULL && wrch == NULL) || rdch != wrch),
            ("bogus %s(), what are you trying to accomplish here?", __func__));
        PCM_BUSYASSERT(d);
        PCM_LOCKASSERT(d);

        simplex = (dsp_get_flags(dev) & SD_F_SIMPLEX) ? 1 : 0;

        /*
         * Scan for free instance entry and put it into the end of list.
         * Create new one if necessary.
         */
        TAILQ_FOREACH(cdi, &d->dsp_cdevinfo_pool, link) {
                if (cdi->busy != 0)
                        break;
                cdi->rdch = rdch;
                cdi->wrch = wrch;
                cdi->volch = volch;
                cdi->simplex = simplex;
                cdi->busy = 1;
                TAILQ_REMOVE(&d->dsp_cdevinfo_pool, cdi, link);
                TAILQ_INSERT_TAIL(&d->dsp_cdevinfo_pool, cdi, link);
                dev->si_drv1 = cdi;
                return;
        }
        PCM_UNLOCK(d);
        cdi = kmalloc(sizeof(*cdi), M_DEVBUF, M_WAITOK | M_ZERO);
        PCM_LOCK(d);
        cdi->rdch = rdch;
        cdi->wrch = wrch;
        cdi->volch = volch;
        cdi->simplex = simplex;
        cdi->busy = 1;
        TAILQ_INSERT_TAIL(&d->dsp_cdevinfo_pool, cdi, link);
        dev->si_drv1 = cdi;
}

static void
dsp_cdevinfo_free(struct cdev *dev)
{
        struct snddev_info *d;
        struct dsp_cdevinfo *cdi, *tmp;
        uint32_t flags;
        int i;

        d = dsp_get_info(dev);

        KASSERT(PCM_REGISTERED(d) && dev != NULL && dev->si_drv1 != NULL &&
            PCM_RDCH(dev) == NULL && PCM_WRCH(dev) == NULL &&
            PCM_VOLCH(dev) == NULL,
            ("bogus %s(), what are you trying to accomplish here?", __func__));
        PCM_BUSYASSERT(d);
        PCM_LOCKASSERT(d);

        cdi = dev->si_drv1;
        dev->si_drv1 = NULL;
        cdi->rdch = NULL;
        cdi->wrch = NULL;
        cdi->volch = NULL;
        cdi->simplex = 0;
        cdi->busy = 0;

        /*
         * Once it is free, move it back to the beginning of list for
         * faster new entry allocation.
         */
        TAILQ_REMOVE(&d->dsp_cdevinfo_pool, cdi, link);
        TAILQ_INSERT_HEAD(&d->dsp_cdevinfo_pool, cdi, link);

        /*
         * Scan the list, cache free entries up to DSP_CDEVINFO_CACHESIZE.
         * Reset simplex flags.
         */
        flags = dsp_get_flags(dev) & ~SD_F_PRIO_SET;
        i = DSP_CDEVINFO_CACHESIZE;
        TAILQ_FOREACH_MUTABLE(cdi, &d->dsp_cdevinfo_pool, link, tmp) {
                if (cdi->busy != 0) {
                        if (cdi->simplex == 0) {
                                if (cdi->rdch != NULL)
                                        flags |= SD_F_PRIO_RD;
                                if (cdi->wrch != NULL)
                                        flags |= SD_F_PRIO_WR;
                        }
                } else {
                        if (i == 0) {
                                TAILQ_REMOVE(&d->dsp_cdevinfo_pool, cdi, link);
                                kfree(cdi, M_DEVBUF);
                        } else
                                i--;
                }
        }
        dsp_set_flags(dev, flags);
}

void
dsp_cdevinfo_init(struct snddev_info *d)
{
        struct dsp_cdevinfo *cdi;
        int i;

        KASSERT(d != NULL, ("NULL snddev_info"));
        PCM_BUSYASSERT(d);
        PCM_UNLOCKASSERT(d);

        TAILQ_INIT(&d->dsp_cdevinfo_pool);
        for (i = 0; i < DSP_CDEVINFO_CACHESIZE; i++) {
                cdi = kmalloc(sizeof(*cdi), M_DEVBUF, M_WAITOK | M_ZERO);
                TAILQ_INSERT_HEAD(&d->dsp_cdevinfo_pool, cdi, link);
        }
}

void
dsp_cdevinfo_flush(struct snddev_info *d)
{
        struct dsp_cdevinfo *cdi, *tmp;

        KASSERT(d != NULL, ("NULL snddev_info"));
        PCM_BUSYASSERT(d);
        PCM_UNLOCKASSERT(d);

        cdi = TAILQ_FIRST(&d->dsp_cdevinfo_pool);
        while (cdi != NULL) {
                tmp = TAILQ_NEXT(cdi, link);
                kfree(cdi, M_DEVBUF);
                cdi = tmp;
        }
        TAILQ_INIT(&d->dsp_cdevinfo_pool);
}

/* duplex / simplex cdev type */
enum {
        DSP_CDEV_TYPE_RDONLY,           /* simplex read-only (record)   */
        DSP_CDEV_TYPE_WRONLY,           /* simplex write-only (play)    */
        DSP_CDEV_TYPE_RDWR              /* duplex read, write, or both  */
};

enum {
        DSP_CDEV_VOLCTL_NONE,
        DSP_CDEV_VOLCTL_READ,
        DSP_CDEV_VOLCTL_WRITE
};

#define DSP_F_VALID(x)          ((x) & (FREAD | FWRITE))
#define DSP_F_DUPLEX(x)         (((x) & (FREAD | FWRITE)) == (FREAD | FWRITE))
#define DSP_F_SIMPLEX(x)        (!DSP_F_DUPLEX(x))
#define DSP_F_READ(x)           ((x) & FREAD)
#define DSP_F_WRITE(x)          ((x) & FWRITE)

static const struct {
        int type;
        char *name;
        char *sep;
        char *alias;
        int use_sep;
        int hw;
        int max;
        int volctl;
        uint32_t fmt, spd;
        int query;
} dsp_cdevs[] = {
        { SND_DEV_DSP,         "dsp",    ".", NULL, 0, 0, 0, 0,
          SND_FORMAT(AFMT_U8, 1, 0),     DSP_DEFAULT_SPEED,
          DSP_CDEV_TYPE_RDWR },
        { SND_DEV_AUDIO,       "audio",  ".", NULL, 0, 0, 0, 0,
          SND_FORMAT(AFMT_MU_LAW, 1, 0), DSP_DEFAULT_SPEED,
          DSP_CDEV_TYPE_RDWR },
        { SND_DEV_DSP16,       "dspW",   ".", NULL, 0, 0, 0, 0,
          SND_FORMAT(AFMT_S16_LE, 1, 0), DSP_DEFAULT_SPEED,
          DSP_CDEV_TYPE_RDWR },
        { SND_DEV_DSPHW_PLAY,  "dsp",   ".p", NULL, 1, 1, SND_MAXHWCHAN, 1,
          SND_FORMAT(AFMT_S16_LE, 2, 0), 48000, DSP_CDEV_TYPE_WRONLY },
        { SND_DEV_DSPHW_VPLAY, "dsp",  ".vp", NULL, 1, 1, SND_MAXVCHANS, 1,
          SND_FORMAT(AFMT_S16_LE, 2, 0), 48000, DSP_CDEV_TYPE_WRONLY },
        { SND_DEV_DSPHW_REC,   "dsp",   ".r", NULL, 1, 1, SND_MAXHWCHAN, 1,
          SND_FORMAT(AFMT_S16_LE, 2, 0), 48000, DSP_CDEV_TYPE_RDONLY },
        { SND_DEV_DSPHW_VREC,  "dsp",  ".vr", NULL, 1, 1, SND_MAXVCHANS, 1,
          SND_FORMAT(AFMT_S16_LE, 2, 0), 48000, DSP_CDEV_TYPE_RDONLY },
        { SND_DEV_DSPHW_CD,    "dspcd",  ".", NULL, 0, 0, 0, 0,
          SND_FORMAT(AFMT_S16_LE, 2, 0), 44100, DSP_CDEV_TYPE_RDWR   },
        /* Low priority, OSSv4 aliases. */
        { SND_DEV_DSP,      "dsp_ac3",   ".", "dsp", 0, 0, 0, 0,
          SND_FORMAT(AFMT_U8, 1, 0),     DSP_DEFAULT_SPEED,
          DSP_CDEV_TYPE_RDWR },
        { SND_DEV_DSP,     "dsp_mmap",   ".", "dsp", 0, 0, 0, 0,
          SND_FORMAT(AFMT_U8, 1, 0),     DSP_DEFAULT_SPEED,
          DSP_CDEV_TYPE_RDWR },
        { SND_DEV_DSP,  "dsp_multich",   ".", "dsp", 0, 0, 0, 0,
          SND_FORMAT(AFMT_U8, 1, 0),     DSP_DEFAULT_SPEED,
          DSP_CDEV_TYPE_RDWR },
        { SND_DEV_DSP, "dsp_spdifout",   ".", "dsp", 0, 0, 0, 0,
          SND_FORMAT(AFMT_U8, 1, 0),     DSP_DEFAULT_SPEED,
          DSP_CDEV_TYPE_RDWR },
        { SND_DEV_DSP,  "dsp_spdifin",   ".", "dsp", 0, 0, 0, 0,
          SND_FORMAT(AFMT_U8, 1, 0),     DSP_DEFAULT_SPEED,
          DSP_CDEV_TYPE_RDWR },
};

#define DSP_FIXUP_ERROR()               do {                            \
        prio = dsp_get_flags(i_dev);                                    \
        if (!DSP_F_VALID(flags))                                        \
                error = EINVAL;                                         \
        if (!DSP_F_DUPLEX(flags) &&                                     \
            ((DSP_F_READ(flags) && d->reccount == 0) ||                 \
            (DSP_F_WRITE(flags) && d->playcount == 0)))                 \
                error = ENOTSUP;                                        \
        else if (!DSP_F_DUPLEX(flags) && (prio & SD_F_SIMPLEX) &&       \
            ((DSP_F_READ(flags) && (prio & SD_F_PRIO_WR)) ||            \
            (DSP_F_WRITE(flags) && (prio & SD_F_PRIO_RD))))             \
                error = EBUSY;                                          \
        else if (DSP_REGISTERED(d, i_dev))                              \
                error = EBUSY;                                          \
} while (0)

static int
dsp_open(struct dev_open_args *ap)
{
        struct cdev *i_dev = ap->a_head.a_dev;
        int flags = ap->a_oflags;
        struct pcm_channel *rdch, *wrch;
        struct snddev_info *d;
        uint32_t fmt, spd, prio, volctl;
        int i, error, rderror, wrerror, devtype, wdevunit, rdevunit;

        /* Kind of impossible.. */
        if (i_dev == NULL)
                return (ENODEV);

        d = dsp_get_info(i_dev);
        if (!PCM_REGISTERED(d))
                return (EBADF);

        PCM_GIANT_ENTER(d);

        /* Lock snddev so nobody else can monkey with it. */
        PCM_LOCK(d);
        PCM_WAIT(d);

        /*
         * Try to acquire cloned device before someone else pick it.
         * ENODEV means this is not a cloned droids.
         */
        error = snd_clone_acquire(i_dev);
        if (!(error == 0 || error == ENODEV)) {
                DSP_FIXUP_ERROR();
                PCM_UNLOCK(d);
                PCM_GIANT_EXIT(d);
                return (error);
        }

        error = 0;
        DSP_FIXUP_ERROR();

        if (error != 0) {
                (void)snd_clone_release(i_dev);
                PCM_UNLOCK(d);
                PCM_GIANT_EXIT(d);
                return (error);
        }

        /*
         * That is just enough. Acquire and unlock pcm lock so
         * the other will just have to wait until we finish doing
         * everything.
         */
        PCM_ACQUIRE(d);
        PCM_UNLOCK(d);

        devtype = PCMDEV(i_dev);
        wdevunit = -1;
        rdevunit = -1;
        fmt = 0;
        spd = 0;
        volctl = DSP_CDEV_VOLCTL_NONE;

        for (i = 0; i < (sizeof(dsp_cdevs) / sizeof(dsp_cdevs[0])); i++) {
                if (devtype != dsp_cdevs[i].type || dsp_cdevs[i].alias != NULL)
                        continue;
                /*
                 * Volume control only valid for DSPHW devices,
                 * and it must be opened in opposite direction be it
                 * simplex or duplex. Anything else will be handled
                 * as usual.
                 */
                if (dsp_cdevs[i].query == DSP_CDEV_TYPE_WRONLY) {
                        if (dsp_cdevs[i].volctl != 0 &&
                            DSP_F_READ(flags)) {
                                volctl = DSP_CDEV_VOLCTL_WRITE;
                                flags &= ~FREAD;
                                flags |= FWRITE;
                        }
                        if (DSP_F_READ(flags)) {
                                (void)snd_clone_release(i_dev);
                                PCM_RELEASE_QUICK(d);
                                PCM_GIANT_EXIT(d);
                                return (ENOTSUP);
                        }
                        wdevunit = dev2unit(i_dev);
                } else if (dsp_cdevs[i].query == DSP_CDEV_TYPE_RDONLY) {
                        if (dsp_cdevs[i].volctl != 0 &&
                            DSP_F_WRITE(flags)) {
                                volctl = DSP_CDEV_VOLCTL_READ;
                                flags &= ~FWRITE;
                                flags |= FREAD;
                        }
                        if (DSP_F_WRITE(flags)) {
                                (void)snd_clone_release(i_dev);
                                PCM_RELEASE_QUICK(d);
                                PCM_GIANT_EXIT(d);
                                return (ENOTSUP);
                        }
                        rdevunit = dev2unit(i_dev);
                }
                fmt = dsp_cdevs[i].fmt;
                spd = dsp_cdevs[i].spd;
                break;
        }

        rdch = NULL;
        wrch = NULL;
        rderror = 0;
        wrerror = 0;

        /*
         * if we get here, the open request is valid- either:
         *   * we were previously not open
         *   * we were open for play xor record and the opener wants
         *     the non-open direction
         */
        if (DSP_F_READ(flags)) {
                /* open for read */
                rderror = pcm_chnalloc(d, &rdch, PCMDIR_REC,
                    curproc->p_pid, curproc->p_comm, rdevunit);

                if (rderror == 0 && chn_reset(rdch, fmt, spd) != 0)
                        rderror = ENXIO;

                if (volctl == DSP_CDEV_VOLCTL_READ)
                        rderror = 0;

                if (rderror != 0) {
                        if (rdch != NULL)
                                pcm_chnrelease(rdch);
                        if (!DSP_F_DUPLEX(flags)) {
                                (void)snd_clone_release(i_dev);
                                PCM_RELEASE_QUICK(d);
                                PCM_GIANT_EXIT(d);
                                return (rderror);
                        }
                        rdch = NULL;
                } else if (volctl == DSP_CDEV_VOLCTL_READ) {
                        if (rdch != NULL) {
                                pcm_chnref(rdch, 1);
                                pcm_chnrelease(rdch);
                        }
                } else {
                        if (flags & O_EXCL)
                                rdch->flags |= CHN_F_EXCLUSIVE;
                        pcm_chnref(rdch, 1);
                        if (volctl == DSP_CDEV_VOLCTL_NONE)
                                chn_vpc_reset(rdch, SND_VOL_C_PCM, 0);
                        CHN_UNLOCK(rdch);
                }
        }

        if (DSP_F_WRITE(flags)) {
                /* open for write */
                wrerror = pcm_chnalloc(d, &wrch, PCMDIR_PLAY,
                    curproc->p_pid, curproc->p_comm, wdevunit);

                if (wrerror == 0 && chn_reset(wrch, fmt, spd) != 0)
                        wrerror = ENXIO;

                if (volctl == DSP_CDEV_VOLCTL_WRITE)
                        wrerror = 0;

                if (wrerror != 0) {
                        if (wrch != NULL)
                                pcm_chnrelease(wrch);
                        if (!DSP_F_DUPLEX(flags)) {
                                if (rdch != NULL) {
                                        /*
                                         * Lock, deref and release previously
                                         * created record channel
                                         */
                                        CHN_LOCK(rdch);
                                        pcm_chnref(rdch, -1);
                                        pcm_chnrelease(rdch);
                                }
                                (void)snd_clone_release(i_dev);
                                PCM_RELEASE_QUICK(d);
                                PCM_GIANT_EXIT(d);
                                return (wrerror);
                        }
                        wrch = NULL;
                } else if (volctl == DSP_CDEV_VOLCTL_WRITE) {
                        if (wrch != NULL) {
                                pcm_chnref(wrch, 1);
                                pcm_chnrelease(wrch);
                        }
                } else {
                        if (flags & O_EXCL)
                                wrch->flags |= CHN_F_EXCLUSIVE;
                        pcm_chnref(wrch, 1);
                        if (volctl == DSP_CDEV_VOLCTL_NONE)
                                chn_vpc_reset(wrch, SND_VOL_C_PCM, 0);
                        CHN_UNLOCK(wrch);
                }
        }


        PCM_LOCK(d);

        /*
         * We're done. Allocate channels information for this cdev.
         */
        switch (volctl) {
        case DSP_CDEV_VOLCTL_READ:
                KASSERT(wrch == NULL, ("wrch=%p not null!", wrch));
                dsp_cdevinfo_alloc(i_dev, NULL, NULL, rdch);
                break;
        case DSP_CDEV_VOLCTL_WRITE:
                KASSERT(rdch == NULL, ("rdch=%p not null!", rdch));
                dsp_cdevinfo_alloc(i_dev, NULL, NULL, wrch);
                break;
        case DSP_CDEV_VOLCTL_NONE:
        default:
                if (wrch == NULL && rdch == NULL) {
                        (void)snd_clone_release(i_dev);
                        PCM_RELEASE(d);
                        PCM_UNLOCK(d);
                        PCM_GIANT_EXIT(d);
                        if (wrerror != 0)
                                return (wrerror);
                        if (rderror != 0)
                                return (rderror);
                        return (EINVAL);
                }
                dsp_cdevinfo_alloc(i_dev, rdch, wrch, NULL);
                if (rdch != NULL)
                        CHN_INSERT_HEAD(d, rdch, channels.pcm.opened);
                if (wrch != NULL)
                        CHN_INSERT_HEAD(d, wrch, channels.pcm.opened);
                break;
        }

        /*
         * Increase clone refcount for its automatic garbage collector.
         */
        (void)snd_clone_ref(i_dev);

        PCM_RELEASE(d);
        PCM_UNLOCK(d);

        PCM_GIANT_LEAVE(d);

        return (0);
}

static int
dsp_close(struct dev_close_args *ap)
{
        struct cdev *i_dev = ap->a_head.a_dev;
        struct pcm_channel *rdch, *wrch, *volch;
        struct snddev_info *d;
        int sg_ids, rdref, wdref;
        int subunit;

        /*
         * subunit is a unique number for the cloned device, it
         * does NOT represent the virtual device channel.
         */
        subunit = PCMSUBUNIT(i_dev);

        d = dsp_get_info(i_dev);
        if (!DSP_REGISTERED(d, i_dev))
                return (EBADF);

        PCM_GIANT_ENTER(d);

        PCM_LOCK(d);
        PCM_WAIT(d);
        PCM_ACQUIRE(d);

        rdch = PCM_RDCH(i_dev);
        wrch = PCM_WRCH(i_dev);
        volch = PCM_VOLCH(i_dev);

        PCM_RDCH(i_dev) = NULL;
        PCM_WRCH(i_dev) = NULL;
        PCM_VOLCH(i_dev) = NULL;

        rdref = -1;
        wdref = -1;

        if (volch != NULL) {
                if (volch == rdch)
                        rdref--;
                else if (volch == wrch)
                        wdref--;
                else {
                        CHN_LOCK(volch);
                        pcm_chnref(volch, -1);
                        CHN_UNLOCK(volch);
                }
        }

        if (rdch != NULL)
                CHN_REMOVE(d, rdch, channels.pcm.opened);
        if (wrch != NULL)
                CHN_REMOVE(d, wrch, channels.pcm.opened);

        if (rdch != NULL || wrch != NULL) {
                PCM_UNLOCK(d);
                if (rdch != NULL) {
                        /*
                         * The channel itself need not be locked because:
                         *   a)  Adding a channel to a syncgroup happens only
                         *       in dsp_ioctl(), which cannot run concurrently
                         *       to dsp_close().
                         *   b)  The syncmember pointer (sm) is protected by
                         *       the global syncgroup list lock.
                         *   c)  A channel can't just disappear, invalidating
                         *       pointers, unless it's closed/dereferenced
                         *       first.
                         */
                        PCM_SG_LOCK();
                        sg_ids = chn_syncdestroy(rdch);
                        PCM_SG_UNLOCK();
                        if (sg_ids != 0)
                                free_unr(pcmsg_unrhdr, sg_ids);

                        CHN_LOCK(rdch);
                        pcm_chnref(rdch, rdref);
                        chn_abort(rdch); /* won't sleep */
                        rdch->flags &= ~(CHN_F_RUNNING | CHN_F_MMAP |
                            CHN_F_DEAD | CHN_F_EXCLUSIVE);
                        chn_reset(rdch, 0, 0);
                        pcm_chnrelease(rdch);
                }
                if (wrch != NULL) {
                        /*
                         * Please see block above.
                         */
                        PCM_SG_LOCK();
                        sg_ids = chn_syncdestroy(wrch);
                        PCM_SG_UNLOCK();
                        if (sg_ids != 0)
                                free_unr(pcmsg_unrhdr, sg_ids);

                        CHN_LOCK(wrch);
                        pcm_chnref(wrch, wdref);
                        chn_flush(wrch); /* may sleep */
                        wrch->flags &= ~(CHN_F_RUNNING | CHN_F_MMAP |
                            CHN_F_DEAD | CHN_F_EXCLUSIVE);
                        chn_reset(wrch, 0, 0);
                        pcm_chnrelease(wrch);
                }
                PCM_LOCK(d);
        }

        dsp_cdevinfo_free(i_dev);
        /*
         * Release clone busy state and unref it so the automatic
         * garbage collector will get the hint and do the remaining
         * cleanup process.
         */
        (void)snd_clone_release(i_dev);

        /*
         * destroy_dev() might sleep, so release pcm lock
         * here and rely on pcm cv serialization.
         */
        PCM_UNLOCK(d);
        (void)snd_clone_unref(i_dev);
        PCM_LOCK(d);

        PCM_RELEASE(d);
        PCM_UNLOCK(d);

        PCM_GIANT_LEAVE(d);

        /*
         * PCMCHAN(i_dev) is not the actual channel but instead is
         * simply the unique subunit we assigned to the clone device.
         *
         * We do not do this here but instead do it when the clone is
         * GCd.
         */
        /*
        devfs_clone_bitmap_put(&DEVFS_CLONE_BITMAP(dsp), subunit);
        */

        return (0);
}

static __inline int
dsp_io_ops(struct cdev *i_dev, struct uio *buf, int ioflags)
{
        struct snddev_info *d;
        struct pcm_channel **ch, *rdch, *wrch;
        int (*chn_io)(struct pcm_channel *, struct uio *, int);
        int prio, ret;
        pid_t runpid;

        KASSERT(i_dev != NULL && buf != NULL &&
            (buf->uio_rw == UIO_READ || buf->uio_rw == UIO_WRITE),
            ("%s(): io train wreck!", __func__));

        d = dsp_get_info(i_dev);
        if (!DSP_REGISTERED(d, i_dev))
                return (EBADF);

        PCM_GIANT_ENTER(d);

        switch (buf->uio_rw) {
        case UIO_READ:
                prio = SD_F_PRIO_RD;
                ch = &rdch;
                chn_io = chn_read;
                break;
        case UIO_WRITE:
                prio = SD_F_PRIO_WR;
                ch = &wrch;
                chn_io = chn_write;
                break;
        default:
                panic("invalid/corrupted uio direction: %d", buf->uio_rw);
                break;
        }

        rdch = NULL;
        wrch = NULL;
        runpid = buf->uio_td->td_proc->p_pid;

        getchns(i_dev, &rdch, &wrch, prio);

        if (*ch == NULL || !((*ch)->flags & CHN_F_BUSY)) {
                PCM_GIANT_EXIT(d);
                return (EBADF);
        }

        if (((*ch)->flags & (CHN_F_MMAP | CHN_F_DEAD)) ||
            (((*ch)->flags & CHN_F_RUNNING) && (*ch)->pid != runpid)) {
                relchns(i_dev, rdch, wrch, prio);
                PCM_GIANT_EXIT(d);
                return (EINVAL);
        } else if (!((*ch)->flags & CHN_F_RUNNING)) {
                (*ch)->flags |= CHN_F_RUNNING;
                (*ch)->pid = runpid;
        }

        /*
         * chn_read/write must give up channel lock in order to copy bytes
         * from/to userland, so up the "in progress" counter to make sure
         * someone else doesn't come along and muss up the buffer.
         */
        ++(*ch)->inprog;
        ret = chn_io(*ch, buf, ioflags);
        --(*ch)->inprog;

        CHN_BROADCAST(&(*ch)->cv);

        relchns(i_dev, rdch, wrch, prio);

        PCM_GIANT_LEAVE(d);

        return (ret);
}

static int
dsp_read(struct dev_read_args *ap)
{
        struct cdev *i_dev = ap->a_head.a_dev;
        struct uio *buf = ap->a_uio;

        return (dsp_io_ops(i_dev, buf, ap->a_ioflag));
}

static int
dsp_write(struct dev_write_args *ap)
{
        struct cdev *i_dev = ap->a_head.a_dev;
        struct uio *buf = ap->a_uio;

        return (dsp_io_ops(i_dev, buf, ap->a_ioflag));
}

static int
dsp_get_volume_channel(struct cdev *dev, struct pcm_channel **volch)
{
        struct snddev_info *d;
        struct pcm_channel *c;
        int unit;

        KASSERT(dev != NULL && volch != NULL,
            ("%s(): NULL query dev=%p volch=%p", __func__, dev, volch));

        d = dsp_get_info(dev);
        if (!PCM_REGISTERED(d)) {
                *volch = NULL;
                return (EINVAL);
        }

        PCM_UNLOCKASSERT(d);

        *volch = NULL;

        c = PCM_VOLCH(dev);
        if (c != NULL) {
                if (!(c->feederflags & (1 << FEEDER_VOLUME)))
                        return (-1);
                *volch = c;
                return (0);
        }

        PCM_LOCK(d);
        PCM_WAIT(d);
        PCM_ACQUIRE(d);

        unit = dev2unit(dev);

        CHN_FOREACH(c, d, channels.pcm) {
                CHN_LOCK(c);
                if (c->unit != unit) {
                        CHN_UNLOCK(c);
                        continue;
                }
                *volch = c;
                pcm_chnref(c, 1);
                PCM_VOLCH(dev) = c;
                CHN_UNLOCK(c);
                PCM_RELEASE(d);
                PCM_UNLOCK(d);
                return ((c->feederflags & (1 << FEEDER_VOLUME)) ? 0 : -1);
        }

        PCM_RELEASE(d);
        PCM_UNLOCK(d);

        return (EINVAL);
}

static int
dsp_ioctl_channel(struct cdev *dev, struct pcm_channel *volch, u_long cmd,
    caddr_t arg)
{
        struct snddev_info *d;
        struct pcm_channel *rdch, *wrch;
        int j, devtype, ret;

        d = dsp_get_info(dev);
        if (!PCM_REGISTERED(d) || !(dsp_get_flags(dev) & SD_F_VPC))
                return (-1);

        PCM_UNLOCKASSERT(d);

        j = cmd & 0xff;

        rdch = PCM_RDCH(dev);
        wrch = PCM_WRCH(dev);

        /* No specific channel, look into cache */
        if (volch == NULL)
                volch = PCM_VOLCH(dev);

        /* Look harder */
        if (volch == NULL) {
                if (j == SOUND_MIXER_RECLEV && rdch != NULL)
                        volch = rdch;
                else if (j == SOUND_MIXER_PCM && wrch != NULL)
                        volch = wrch;
        }

        devtype = PCMDEV(dev);

        /* Look super harder */
        if (volch == NULL &&
            (devtype == SND_DEV_DSPHW_PLAY || devtype == SND_DEV_DSPHW_VPLAY ||
            devtype == SND_DEV_DSPHW_REC || devtype == SND_DEV_DSPHW_VREC)) {
                ret = dsp_get_volume_channel(dev, &volch);
                if (ret != 0)
                        return (ret);
                if (volch == NULL)
                        return (EINVAL);
        }

        /* Final validation */
        if (volch != NULL) {
                CHN_LOCK(volch);
                if (!(volch->feederflags & (1 << FEEDER_VOLUME))) {
                        CHN_UNLOCK(volch);
                        return (-1);
                }
                if (volch->direction == PCMDIR_PLAY)
                        wrch = volch;
                else
                        rdch = volch;
        }

        ret = EINVAL;

        if (volch != NULL &&
            ((j == SOUND_MIXER_PCM && volch->direction == PCMDIR_PLAY) ||
            (j == SOUND_MIXER_RECLEV && volch->direction == PCMDIR_REC))) {
                if ((cmd & ~0xff) == MIXER_WRITE(0)) {
                        int left, right, center;

                        left = *(int *)arg & 0x7f;
                        right = ((*(int *)arg) >> 8) & 0x7f;
                        center = (left + right) >> 1;
                        chn_setvolume_multi(volch, SND_VOL_C_PCM, left, right,
                            center);
                } else if ((cmd & ~0xff) == MIXER_READ(0)) {
                        *(int *)arg = CHN_GETVOLUME(volch,
                                SND_VOL_C_PCM, SND_CHN_T_FL);
                        *(int *)arg |= CHN_GETVOLUME(volch,
                                SND_VOL_C_PCM, SND_CHN_T_FR) << 8;
                }
                ret = 0;
        } else if (rdch != NULL || wrch != NULL) {
                switch (j) {
                case SOUND_MIXER_DEVMASK:
                case SOUND_MIXER_CAPS:
                case SOUND_MIXER_STEREODEVS:
                        if ((cmd & ~0xff) == MIXER_READ(0)) {
                                *(int *)arg = 0;
                                if (rdch != NULL)
                                        *(int *)arg |= SOUND_MASK_RECLEV;
                                if (wrch != NULL)
                                        *(int *)arg |= SOUND_MASK_PCM;
                        }
                        ret = 0;
                        break;
                case SOUND_MIXER_RECMASK:
                case SOUND_MIXER_RECSRC:
                        if ((cmd & ~0xff) == MIXER_READ(0))
                                *(int *)arg = 0;
                        ret = 0;
                        break;
                default:
                        break;
                }
        }

        if (volch != NULL)
                CHN_UNLOCK(volch);

        return (ret);
}

static int
dsp_ioctl(struct dev_ioctl_args *ap)
{
        struct cdev *i_dev = ap->a_head.a_dev;
        u_long cmd = ap->a_cmd;
        caddr_t arg = ap->a_data;
        struct pcm_channel *chn, *rdch, *wrch;
        struct snddev_info *d;
        u_long xcmd;
        int *arg_i, ret, tmp;

        d = dsp_get_info(i_dev);
        if (!DSP_REGISTERED(d, i_dev))
                return (EBADF);

        PCM_GIANT_ENTER(d);

        arg_i = (int *)arg;
        ret = 0;
        xcmd = 0;
        chn = NULL;

        if (IOCGROUP(cmd) == 'M') {
                if (cmd == OSS_GETVERSION) {
                        *arg_i = SOUND_VERSION;
                        PCM_GIANT_EXIT(d);
                        return (0);
                }
                ret = dsp_ioctl_channel(i_dev, PCM_VOLCH(i_dev), cmd, arg);
                if (ret != -1) {
                        PCM_GIANT_EXIT(d);
                        return (ret);
                }

                if (d->mixer_dev != NULL) {
                        PCM_ACQUIRE_QUICK(d);
                        ret = mixer_ioctl_cmd(d->mixer_dev, cmd, arg, -1,
                            MIXER_CMD_DIRECT);
                        PCM_RELEASE_QUICK(d);
                } else
                        ret = EBADF;

                PCM_GIANT_EXIT(d);

                return (ret);
        }

        /*
         * Certain ioctls may be made on any type of device (audio, mixer,
         * and MIDI).  Handle those special cases here.
         */
        if (IOCGROUP(cmd) == 'X') {
                PCM_ACQUIRE_QUICK(d);
                switch(cmd) {
                case SNDCTL_SYSINFO:
                        sound_oss_sysinfo((oss_sysinfo *)arg);
                        break;
                case SNDCTL_CARDINFO:
                        ret = sound_oss_card_info((oss_card_info *)arg);
                        break;
                case SNDCTL_AUDIOINFO:
                case SNDCTL_AUDIOINFO_EX:
                case SNDCTL_ENGINEINFO:
                        ret = dsp_oss_audioinfo(i_dev, (oss_audioinfo *)arg);
                        break;
                case SNDCTL_MIXERINFO:
                        ret = mixer_oss_mixerinfo(i_dev, (oss_mixerinfo *)arg);
                        break;
                default:
                        ret = EINVAL;
                }
                PCM_RELEASE_QUICK(d);
                PCM_GIANT_EXIT(d);
                return (ret);
        }

        getchns(i_dev, &rdch, &wrch, 0);

        if (wrch != NULL && (wrch->flags & CHN_F_DEAD))
                wrch = NULL;
        if (rdch != NULL && (rdch->flags & CHN_F_DEAD))
                rdch = NULL;

        if (wrch == NULL && rdch == NULL) {
                PCM_GIANT_EXIT(d);
                return (EINVAL);
        }

        switch(cmd) {
#ifdef OLDPCM_IOCTL
        /*
         * we start with the new ioctl interface.
         */
        case AIONWRITE: /* how many bytes can write ? */
                if (wrch) {
                        CHN_LOCK(wrch);
/*
                if (wrch && wrch->bufhard.dl)
                        while (chn_wrfeed(wrch) == 0);
*/
                        *arg_i = sndbuf_getfree(wrch->bufsoft);
                        CHN_UNLOCK(wrch);
                } else {
                        *arg_i = 0;
                        ret = EINVAL;
                }
                break;

        case AIOSSIZE:     /* set the current blocksize */
                {
                        struct snd_size *p = (struct snd_size *)arg;

                        p->play_size = 0;
                        p->rec_size = 0;
                        PCM_ACQUIRE_QUICK(d);
                        if (wrch) {
                                CHN_LOCK(wrch);
                                chn_setblocksize(wrch, 2, p->play_size);
                                p->play_size = sndbuf_getblksz(wrch->bufsoft);
                                CHN_UNLOCK(wrch);
                        }
                        if (rdch) {
                                CHN_LOCK(rdch);
                                chn_setblocksize(rdch, 2, p->rec_size);
                                p->rec_size = sndbuf_getblksz(rdch->bufsoft);
                                CHN_UNLOCK(rdch);
                        }
                        PCM_RELEASE_QUICK(d);
                }
                break;
        case AIOGSIZE:  /* get the current blocksize */
                {
                        struct snd_size *p = (struct snd_size *)arg;

                        if (wrch) {
                                CHN_LOCK(wrch);
                                p->play_size = sndbuf_getblksz(wrch->bufsoft);
                                CHN_UNLOCK(wrch);
                        }
                        if (rdch) {
                                CHN_LOCK(rdch);
                                p->rec_size = sndbuf_getblksz(rdch->bufsoft);
                                CHN_UNLOCK(rdch);
                        }
                }
                break;

        case AIOSFMT:
        case AIOGFMT:
                {
                        snd_chan_param *p = (snd_chan_param *)arg;

                        if (cmd == AIOSFMT &&
                            ((p->play_format != 0 && p->play_rate == 0) ||
                            (p->rec_format != 0 && p->rec_rate == 0))) {
                                ret = EINVAL;
                                break;
                        }
                        PCM_ACQUIRE_QUICK(d);
                        if (wrch) {
                                CHN_LOCK(wrch);
                                if (cmd == AIOSFMT && p->play_format != 0) {
                                        chn_setformat(wrch,
                                            SND_FORMAT(p->play_format,
                                            AFMT_CHANNEL(wrch->format),
                                            AFMT_EXTCHANNEL(wrch->format)));
                                        chn_setspeed(wrch, p->play_rate);
                                }
                                p->play_rate = wrch->speed;
                                p->play_format = AFMT_ENCODING(wrch->format);
                                CHN_UNLOCK(wrch);
                        } else {
                                p->play_rate = 0;
                                p->play_format = 0;
                        }
                        if (rdch) {
                                CHN_LOCK(rdch);
                                if (cmd == AIOSFMT && p->rec_format != 0) {
                                        chn_setformat(rdch,
                                            SND_FORMAT(p->rec_format,
                                            AFMT_CHANNEL(rdch->format),
                                            AFMT_EXTCHANNEL(rdch->format)));
                                        chn_setspeed(rdch, p->rec_rate);
                                }
                                p->rec_rate = rdch->speed;
                                p->rec_format = AFMT_ENCODING(rdch->format);
                                CHN_UNLOCK(rdch);
                        } else {
                                p->rec_rate = 0;
                                p->rec_format = 0;
                        }
                        PCM_RELEASE_QUICK(d);
                }
                break;

        case AIOGCAP:     /* get capabilities */
                {
                        snd_capabilities *p = (snd_capabilities *)arg;
                        struct pcmchan_caps *pcaps = NULL, *rcaps = NULL;
                        struct cdev *pdev;

                        PCM_LOCK(d);
                        if (rdch) {
                                CHN_LOCK(rdch);
                                rcaps = chn_getcaps(rdch);
                        }
                        if (wrch) {
                                CHN_LOCK(wrch);
                                pcaps = chn_getcaps(wrch);
                        }
                        p->rate_min = max(rcaps? rcaps->minspeed : 0,
                                          pcaps? pcaps->minspeed : 0);
                        p->rate_max = min(rcaps? rcaps->maxspeed : 1000000,
                                          pcaps? pcaps->maxspeed : 1000000);
                        p->bufsize = min(rdch? sndbuf_getsize(rdch->bufsoft) : 1000000,
                                         wrch? sndbuf_getsize(wrch->bufsoft) : 1000000);
                        /* XXX bad on sb16 */
                        p->formats = (rdch? chn_getformats(rdch) : 0xffffffff) &
                                     (wrch? chn_getformats(wrch) : 0xffffffff);
                        if (rdch && wrch)
                                p->formats |= (dsp_get_flags(i_dev) & SD_F_SIMPLEX)? 0 : AFMT_FULLDUPLEX;
                        pdev = d->mixer_dev;
                        p->mixers = 1; /* default: one mixer */
                        p->inputs = pdev->si_drv1? mix_getdevs(pdev->si_drv1) : 0;
                        p->left = p->right = 100;
                        if (wrch)
                                CHN_UNLOCK(wrch);
                        if (rdch)
                                CHN_UNLOCK(rdch);
                        PCM_UNLOCK(d);
                }
                break;

        case AIOSTOP:
                if (*arg_i == AIOSYNC_PLAY && wrch) {
                        CHN_LOCK(wrch);
                        *arg_i = chn_abort(wrch);
                        CHN_UNLOCK(wrch);
                } else if (*arg_i == AIOSYNC_CAPTURE && rdch) {
                        CHN_LOCK(rdch);
                        *arg_i = chn_abort(rdch);
                        CHN_UNLOCK(rdch);
                } else {
                        kprintf("AIOSTOP: bad channel 0x%x\n", *arg_i);
                        *arg_i = 0;
                }
                break;

        case AIOSYNC:
                kprintf("AIOSYNC chan 0x%03lx pos %lu unimplemented\n",
                        ((snd_sync_parm *)arg)->chan, ((snd_sync_parm *)arg)->pos);
                break;
#endif
        /*
         * here follow the standard ioctls (filio.h etc.)
         */
        case FIONREAD: /* get # bytes to read */
                if (rdch) {
                        CHN_LOCK(rdch);
/*                      if (rdch && rdch->bufhard.dl)
                                while (chn_rdfeed(rdch) == 0);
*/
                        *arg_i = sndbuf_getready(rdch->bufsoft);
                        CHN_UNLOCK(rdch);
                } else {
                        *arg_i = 0;
                        ret = EINVAL;
                }
                break;

        case FIOASYNC: /*set/clear async i/o */
                DEB( kprintf("FIOASYNC\n") ; )
                break;

        case FIONBIO: /* set/clear non-blocking i/o */
                DEB( kprintf("FIONBIO\n") ; )
                break;

        case SNDCTL_DSP_NONBLOCK: /* set non-blocking i/o */
                atomic_set_int(&ap->a_fp->f_flag, FNONBLOCK);
                break;

        /*
         * Finally, here is the linux-compatible ioctl interface
         */
#define THE_REAL_SNDCTL_DSP_GETBLKSIZE _IOWR('P', 4, int)
        case THE_REAL_SNDCTL_DSP_GETBLKSIZE:
        case SNDCTL_DSP_GETBLKSIZE:
                chn = wrch ? wrch : rdch;
                if (chn) {
                        CHN_LOCK(chn);
                        *arg_i = sndbuf_getblksz(chn->bufsoft);
                        CHN_UNLOCK(chn);
                } else {
                        *arg_i = 0;
                        ret = EINVAL;
                }
                break;

        case SNDCTL_DSP_SETBLKSIZE:
                RANGE(*arg_i, 16, 65536);
                PCM_ACQUIRE_QUICK(d);
                if (wrch) {
                        CHN_LOCK(wrch);
                        chn_setblocksize(wrch, 2, *arg_i);
                        CHN_UNLOCK(wrch);
                }
                if (rdch) {
                        CHN_LOCK(rdch);
                        chn_setblocksize(rdch, 2, *arg_i);
                        CHN_UNLOCK(rdch);
                }
                PCM_RELEASE_QUICK(d);
                break;

        case SNDCTL_DSP_RESET:
                DEB(kprintf("dsp reset\n"));
                if (wrch) {
                        CHN_LOCK(wrch);
                        chn_abort(wrch);
                        chn_resetbuf(wrch);
                        CHN_UNLOCK(wrch);
                }
                if (rdch) {
                        CHN_LOCK(rdch);
                        chn_abort(rdch);
                        chn_resetbuf(rdch);
                        CHN_UNLOCK(rdch);
                }
                break;

        case SNDCTL_DSP_SYNC:
                DEB(kprintf("dsp sync\n"));
                /* chn_sync may sleep */
                if (wrch) {
                        CHN_LOCK(wrch);
                        chn_sync(wrch, 0);
                        CHN_UNLOCK(wrch);
                }
                break;

        case SNDCTL_DSP_SPEED:
                /* chn_setspeed may sleep */
                tmp = 0;
                PCM_ACQUIRE_QUICK(d);
                if (wrch) {
                        CHN_LOCK(wrch);
                        ret = chn_setspeed(wrch, *arg_i);
                        tmp = wrch->speed;
                        CHN_UNLOCK(wrch);
                }
                if (rdch && ret == 0) {
                        CHN_LOCK(rdch);
                        ret = chn_setspeed(rdch, *arg_i);
                        if (tmp == 0)
                                tmp = rdch->speed;
                        CHN_UNLOCK(rdch);
                }
                PCM_RELEASE_QUICK(d);
                *arg_i = tmp;
                break;

        case SOUND_PCM_READ_RATE:
                chn = wrch ? wrch : rdch;
                if (chn) {
                        CHN_LOCK(chn);
                        *arg_i = chn->speed;
                        CHN_UNLOCK(chn);
                } else {
                        *arg_i = 0;
                        ret = EINVAL;
                }
                break;

        case SNDCTL_DSP_STEREO:
                tmp = -1;
                *arg_i = (*arg_i)? 2 : 1;
                PCM_ACQUIRE_QUICK(d);
                if (wrch) {
                        CHN_LOCK(wrch);
                        ret = chn_setformat(wrch,
                            SND_FORMAT(wrch->format, *arg_i, 0));
                        tmp = (AFMT_CHANNEL(wrch->format) > 1)? 1 : 0;
                        CHN_UNLOCK(wrch);
                }
                if (rdch && ret == 0) {
                        CHN_LOCK(rdch);
                        ret = chn_setformat(rdch,
                            SND_FORMAT(rdch->format, *arg_i, 0));
                        if (tmp == -1)
                                tmp = (AFMT_CHANNEL(rdch->format) > 1)? 1 : 0;
                        CHN_UNLOCK(rdch);
                }
                PCM_RELEASE_QUICK(d);
                *arg_i = tmp;
                break;

        case SOUND_PCM_WRITE_CHANNELS:
/*      case SNDCTL_DSP_CHANNELS: ( == SOUND_PCM_WRITE_CHANNELS) */
                if (*arg_i < 0) {
                        *arg_i = 0;
                        ret = EINVAL;
                        break;
                }
                if (*arg_i != 0) {
                        struct pcmchan_matrix *m;
                        uint32_t ext;

                        tmp = 0;
                        if (*arg_i > SND_CHN_MAX)
                                *arg_i = SND_CHN_MAX;

                        m = feeder_matrix_default_channel_map(*arg_i);
                        if (m != NULL)
                                ext = m->ext;
                        else
                                ext = 0;

                        PCM_ACQUIRE_QUICK(d);
                        if (wrch) {
                                CHN_LOCK(wrch);
                                ret = chn_setformat(wrch,
                                    SND_FORMAT(wrch->format, *arg_i, ext));
                                tmp = AFMT_CHANNEL(wrch->format);
                                CHN_UNLOCK(wrch);
                        }
                        if (rdch && ret == 0) {
                                CHN_LOCK(rdch);
                                ret = chn_setformat(rdch,
                                    SND_FORMAT(rdch->format, *arg_i, ext));
                                if (tmp == 0)
                                        tmp = AFMT_CHANNEL(rdch->format);
                                CHN_UNLOCK(rdch);
                        }
                        PCM_RELEASE_QUICK(d);
                        *arg_i = tmp;
                } else {
                        chn = wrch ? wrch : rdch;
                        CHN_LOCK(chn);
                        *arg_i = AFMT_CHANNEL(chn->format);
                        CHN_UNLOCK(chn);
                }
                break;

        case SOUND_PCM_READ_CHANNELS:
                chn = wrch ? wrch : rdch;
                if (chn) {
                        CHN_LOCK(chn);
                        *arg_i = AFMT_CHANNEL(chn->format);
                        CHN_UNLOCK(chn);
                } else {
                        *arg_i = 0;
                        ret = EINVAL;
                }
                break;

        case SNDCTL_DSP_GETFMTS:        /* returns a mask of supported fmts */
                chn = wrch ? wrch : rdch;
                if (chn) {
                        CHN_LOCK(chn);
                        *arg_i = chn_getformats(chn);
                        CHN_UNLOCK(chn);
                } else {
                        *arg_i = 0;
                        ret = EINVAL;
                }
                break;

        case SNDCTL_DSP_SETFMT: /* sets _one_ format */
                if (*arg_i != AFMT_QUERY) {
                        tmp = 0;
                        PCM_ACQUIRE_QUICK(d);
                        if (wrch) {
                                CHN_LOCK(wrch);
                                ret = chn_setformat(wrch, SND_FORMAT(*arg_i,
                                    AFMT_CHANNEL(wrch->format),
                                    AFMT_EXTCHANNEL(wrch->format)));
                                tmp = wrch->format;
                                CHN_UNLOCK(wrch);
                        }
                        if (rdch && ret == 0) {
                                CHN_LOCK(rdch);
                                ret = chn_setformat(rdch, SND_FORMAT(*arg_i,
                                    AFMT_CHANNEL(rdch->format),
                                    AFMT_EXTCHANNEL(rdch->format)));
                                if (tmp == 0)
                                        tmp = rdch->format;
                                CHN_UNLOCK(rdch);
                        }
                        PCM_RELEASE_QUICK(d);
                        *arg_i = AFMT_ENCODING(tmp);
                } else {
                        chn = wrch ? wrch : rdch;
                        CHN_LOCK(chn);
                        *arg_i = AFMT_ENCODING(chn->format);
                        CHN_UNLOCK(chn);
                }
                break;

        case SNDCTL_DSP_SETFRAGMENT:
                DEB(kprintf("SNDCTL_DSP_SETFRAGMENT 0x%08x\n", *(int *)arg));
                {
                        uint32_t fragln = (*arg_i) & 0x0000ffff;
                        uint32_t maxfrags = ((*arg_i) & 0xffff0000) >> 16;
                        uint32_t fragsz;
                        uint32_t r_maxfrags, r_fragsz;

                        RANGE(fragln, 4, 16);
                        fragsz = 1 << fragln;

                        if (maxfrags == 0)
                                maxfrags = CHN_2NDBUFMAXSIZE / fragsz;
                        if (maxfrags < 2)
                                maxfrags = 2;
                        if (maxfrags * fragsz > CHN_2NDBUFMAXSIZE)
                                maxfrags = CHN_2NDBUFMAXSIZE / fragsz;

                        DEB(kprintf("SNDCTL_DSP_SETFRAGMENT %d frags, %d sz\n", maxfrags, fragsz));
                        PCM_ACQUIRE_QUICK(d);
                        if (rdch) {
                                CHN_LOCK(rdch);
                                ret = chn_setblocksize(rdch, maxfrags, fragsz);
                                r_maxfrags = sndbuf_getblkcnt(rdch->bufsoft);
                                r_fragsz = sndbuf_getblksz(rdch->bufsoft);
                                CHN_UNLOCK(rdch);
                        } else {
                                r_maxfrags = maxfrags;
                                r_fragsz = fragsz;
                        }
                        if (wrch && ret == 0) {
                                CHN_LOCK(wrch);
                                ret = chn_setblocksize(wrch, maxfrags, fragsz);
                                maxfrags = sndbuf_getblkcnt(wrch->bufsoft);
                                fragsz = sndbuf_getblksz(wrch->bufsoft);
                                CHN_UNLOCK(wrch);
                        } else { /* use whatever came from the read channel */
                                maxfrags = r_maxfrags;
                                fragsz = r_fragsz;
                        }
                        PCM_RELEASE_QUICK(d);

                        fragln = 0;
                        while (fragsz > 1) {
                                fragln++;
                                fragsz >>= 1;
                        }
                        *arg_i = (maxfrags << 16) | fragln;
                }
                break;

        case SNDCTL_DSP_GETISPACE:
                /* return the size of data available in the input queue */
                {
                        audio_buf_info *a = (audio_buf_info *)arg;
                        if (rdch) {
                                struct snd_dbuf *bs = rdch->bufsoft;

                                CHN_LOCK(rdch);
                                a->bytes = sndbuf_getready(bs);
                                a->fragments = a->bytes / sndbuf_getblksz(bs);
                                a->fragstotal = sndbuf_getblkcnt(bs);
                                a->fragsize = sndbuf_getblksz(bs);
                                CHN_UNLOCK(rdch);
                        } else
                                ret = EINVAL;
                }
                break;

        case SNDCTL_DSP_GETOSPACE:
                /* return space available in the output queue */
                {
                        audio_buf_info *a = (audio_buf_info *)arg;
                        if (wrch) {
                                struct snd_dbuf *bs = wrch->bufsoft;

                                CHN_LOCK(wrch);
                                /* XXX abusive DMA update: chn_wrupdate(wrch); */
                                a->bytes = sndbuf_getfree(bs);
                                a->fragments = a->bytes / sndbuf_getblksz(bs);
                                a->fragstotal = sndbuf_getblkcnt(bs);
                                a->fragsize = sndbuf_getblksz(bs);
                                CHN_UNLOCK(wrch);
                        } else
                                ret = EINVAL;
                }
                break;

        case SNDCTL_DSP_GETIPTR:
                {
                        count_info *a = (count_info *)arg;
                        if (rdch) {
                                struct snd_dbuf *bs = rdch->bufsoft;

                                CHN_LOCK(rdch);
                                /* XXX abusive DMA update: chn_rdupdate(rdch); */
                                a->bytes = sndbuf_gettotal(bs);
                                a->blocks = sndbuf_getblocks(bs) - rdch->blocks;
                                a->ptr = sndbuf_getfreeptr(bs);
                                rdch->blocks = sndbuf_getblocks(bs);
                                CHN_UNLOCK(rdch);
                        } else
                                ret = EINVAL;
                }
                break;

        case SNDCTL_DSP_GETOPTR:
                {
                        count_info *a = (count_info *)arg;
                        if (wrch) {
                                struct snd_dbuf *bs = wrch->bufsoft;

                                CHN_LOCK(wrch);
                                /* XXX abusive DMA update: chn_wrupdate(wrch); */
                                a->bytes = sndbuf_gettotal(bs);
                                a->blocks = sndbuf_getblocks(bs) - wrch->blocks;
                                a->ptr = sndbuf_getreadyptr(bs);
                                wrch->blocks = sndbuf_getblocks(bs);
                                CHN_UNLOCK(wrch);
                        } else
                                ret = EINVAL;
                }
                break;

        case SNDCTL_DSP_GETCAPS:
                PCM_LOCK(d);
                *arg_i = PCM_CAP_REALTIME | PCM_CAP_MMAP | PCM_CAP_TRIGGER;
                if (rdch && wrch && !(dsp_get_flags(i_dev) & SD_F_SIMPLEX))
                        *arg_i |= PCM_CAP_DUPLEX;
                PCM_UNLOCK(d);
                break;

        case SOUND_PCM_READ_BITS:
                chn = wrch ? wrch : rdch;
                if (chn) {
                        CHN_LOCK(chn);
                        if (chn->format & AFMT_8BIT)
                                *arg_i = 8;
                        else if (chn->format & AFMT_16BIT)
                                *arg_i = 16;
                        else if (chn->format & AFMT_24BIT)
                                *arg_i = 24;
                        else if (chn->format & AFMT_32BIT)
                                *arg_i = 32;
                        else
                                ret = EINVAL;
                        CHN_UNLOCK(chn);
                } else {
                        *arg_i = 0;
                        ret = EINVAL;
                }
                break;

        case SNDCTL_DSP_SETTRIGGER:
                if (rdch) {
                        CHN_LOCK(rdch);
                        rdch->flags &= ~CHN_F_NOTRIGGER;
                        if (*arg_i & PCM_ENABLE_INPUT)
                                chn_start(rdch, 1);
                        else {
                                chn_abort(rdch);
                                chn_resetbuf(rdch);
                                rdch->flags |= CHN_F_NOTRIGGER;
                        }
                        CHN_UNLOCK(rdch);
                }
                if (wrch) {
                        CHN_LOCK(wrch);
                        wrch->flags &= ~CHN_F_NOTRIGGER;
                        if (*arg_i & PCM_ENABLE_OUTPUT)
                                chn_start(wrch, 1);
                        else {
                                chn_abort(wrch);
                                chn_resetbuf(wrch);
                                wrch->flags |= CHN_F_NOTRIGGER;
                        }
                        CHN_UNLOCK(wrch);
                }
                break;

        case SNDCTL_DSP_GETTRIGGER:
                *arg_i = 0;
                if (wrch) {
                        CHN_LOCK(wrch);
                        if (wrch->flags & CHN_F_TRIGGERED)
                                *arg_i |= PCM_ENABLE_OUTPUT;
                        CHN_UNLOCK(wrch);
                }
                if (rdch) {
                        CHN_LOCK(rdch);
                        if (rdch->flags & CHN_F_TRIGGERED)
                                *arg_i |= PCM_ENABLE_INPUT;
                        CHN_UNLOCK(rdch);
                }
                break;

        case SNDCTL_DSP_GETODELAY:
                if (wrch) {
                        struct snd_dbuf *bs = wrch->bufsoft;

                        CHN_LOCK(wrch);
                        /* XXX abusive DMA update: chn_wrupdate(wrch); */
                        *arg_i = sndbuf_getready(bs);
                        CHN_UNLOCK(wrch);
                } else
                        ret = EINVAL;
                break;

        case SNDCTL_DSP_POST:
                if (wrch) {
                        CHN_LOCK(wrch);
                        wrch->flags &= ~CHN_F_NOTRIGGER;
                        chn_start(wrch, 1);
                        CHN_UNLOCK(wrch);
                }
                break;

        case SNDCTL_DSP_SETDUPLEX:
                /*
                 * switch to full-duplex mode if card is in half-duplex
                 * mode and is able to work in full-duplex mode
                 */
                PCM_LOCK(d);
                if (rdch && wrch && (dsp_get_flags(i_dev) & SD_F_SIMPLEX))
                        dsp_set_flags(i_dev, dsp_get_flags(i_dev)^SD_F_SIMPLEX);
                PCM_UNLOCK(d);
                break;

        /*
         * The following four ioctls are simple wrappers around mixer_ioctl
         * with no further processing.  xcmd is short for "translated
         * command".
         */
        case SNDCTL_DSP_GETRECVOL:
                if (xcmd == 0) {
                        xcmd = SOUND_MIXER_READ_RECLEV;
                        chn = rdch;
                }
                /* FALLTHROUGH */
        case SNDCTL_DSP_SETRECVOL:
                if (xcmd == 0) {
                        xcmd = SOUND_MIXER_WRITE_RECLEV;
                        chn = rdch;
                }
                /* FALLTHROUGH */
        case SNDCTL_DSP_GETPLAYVOL:
                if (xcmd == 0) {
                        xcmd = SOUND_MIXER_READ_PCM;
                        chn = wrch;
                }
                /* FALLTHROUGH */
        case SNDCTL_DSP_SETPLAYVOL:
                if (xcmd == 0) {
                        xcmd = SOUND_MIXER_WRITE_PCM;
                        chn = wrch;
                }

                ret = dsp_ioctl_channel(i_dev, chn, xcmd, arg);
                if (ret != -1) {
                        PCM_GIANT_EXIT(d);
                        return (ret);
                }

                if (d->mixer_dev != NULL) {
                        PCM_ACQUIRE_QUICK(d);
                        ret = mixer_ioctl_cmd(d->mixer_dev, xcmd, arg, -1,
                            MIXER_CMD_DIRECT);
                        PCM_RELEASE_QUICK(d);
                } else
                        ret = ENOTSUP;

                break;

        case SNDCTL_DSP_GET_RECSRC_NAMES:
        case SNDCTL_DSP_GET_RECSRC:
        case SNDCTL_DSP_SET_RECSRC:
                if (d->mixer_dev != NULL) {
                        PCM_ACQUIRE_QUICK(d);
                        ret = mixer_ioctl_cmd(d->mixer_dev, cmd, arg, -1,
                            MIXER_CMD_DIRECT);
                        PCM_RELEASE_QUICK(d);
                } else
                        ret = ENOTSUP;
                break;

        /*
         * The following 3 ioctls aren't very useful at the moment.  For
         * now, only a single channel is associated with a cdev (/dev/dspN
         * instance), so there's only a single output routing to use (i.e.,
         * the wrch bound to this cdev).
         */
        case SNDCTL_DSP_GET_PLAYTGT_NAMES:
                {
                        oss_mixer_enuminfo *ei;
                        ei = (oss_mixer_enuminfo *)arg;
                        ei->dev = 0;
                        ei->ctrl = 0;
                        ei->version = 0; /* static for now */
                        ei->strindex[0] = 0;

                        if (wrch != NULL) {
                                ei->nvalues = 1;
                                strlcpy(ei->strings, wrch->name,
                                        sizeof(ei->strings));
                        } else {
                                ei->nvalues = 0;
                                ei->strings[0] = '\0';
                        }
                }
                break;
        case SNDCTL_DSP_GET_PLAYTGT:
        case SNDCTL_DSP_SET_PLAYTGT:    /* yes, they are the same for now */
                /*
                 * Re: SET_PLAYTGT
                 *   OSSv4: "The value that was accepted by the device will
                 *   be returned back in the variable pointed by the
                 *   argument."
                 */
                if (wrch != NULL)
                        *arg_i = 0;
                else
                        ret = EINVAL;
                break;

        case SNDCTL_DSP_SILENCE:
        /*
         * Flush the software (pre-feed) buffer, but try to minimize playback
         * interruption.  (I.e., record unplayed samples with intent to
         * restore by SNDCTL_DSP_SKIP.) Intended for application "pause"
         * functionality.
         */
                if (wrch == NULL)
                        ret = EINVAL;
                else {
                        struct snd_dbuf *bs;
                        CHN_LOCK(wrch);
                        while (wrch->inprog != 0)
                                cv_wait(&wrch->cv, wrch->lock);
                        bs = wrch->bufsoft;
                        if ((bs->shadbuf != NULL) && (sndbuf_getready(bs) > 0)) {
                                bs->sl = sndbuf_getready(bs);
                                sndbuf_dispose(bs, bs->shadbuf, sndbuf_getready(bs));
                                sndbuf_fillsilence(bs);
                                chn_start(wrch, 0);
                        }
                        CHN_UNLOCK(wrch);
                }
                break;

        case SNDCTL_DSP_SKIP:
        /*
         * OSSv4 docs: "This ioctl call discards all unplayed samples in the
         * playback buffer by moving the current write position immediately
         * before the point where the device is currently reading the samples."
         */
                if (wrch == NULL)
                        ret = EINVAL;
                else {
                        struct snd_dbuf *bs;
                        CHN_LOCK(wrch);
                        while (wrch->inprog != 0)
                                cv_wait(&wrch->cv, wrch->lock);
                        bs = wrch->bufsoft;
                        if ((bs->shadbuf != NULL) && (bs->sl > 0)) {
                                sndbuf_softreset(bs);
                                sndbuf_acquire(bs, bs->shadbuf, bs->sl);
                                bs->sl = 0;
                                chn_start(wrch, 0);
                        }
                        CHN_UNLOCK(wrch);
                }
                break;

        case SNDCTL_DSP_CURRENT_OPTR:
        case SNDCTL_DSP_CURRENT_IPTR:
        /**
         * @note Changing formats resets the buffer counters, which differs
         *       from the 4Front drivers.  However, I don't expect this to be
         *       much of a problem.
         *
         * @note In a test where @c CURRENT_OPTR is called immediately after write
         *       returns, this driver is about 32K samples behind whereas
         *       4Front's is about 8K samples behind.  Should determine source
         *       of discrepancy, even if only out of curiosity.
         *
         * @todo Actually test SNDCTL_DSP_CURRENT_IPTR.
         */
                chn = (cmd == SNDCTL_DSP_CURRENT_OPTR) ? wrch : rdch;
                if (chn == NULL) 
                        ret = EINVAL;
                else {
                        struct snd_dbuf *bs;
                        /* int tmp; */

                        oss_count_t *oc = (oss_count_t *)arg;

                        CHN_LOCK(chn);
                        bs = chn->bufsoft;
#if 0
                        tmp = (sndbuf_getsize(b) + chn_getptr(chn) - sndbuf_gethwptr(b)) % sndbuf_getsize(b);
                        oc->samples = (sndbuf_gettotal(b) + tmp) / sndbuf_getalign(b);
                        oc->fifo_samples = (sndbuf_getready(b) - tmp) / sndbuf_getalign(b);
#else
                        oc->samples = sndbuf_gettotal(bs) / sndbuf_getalign(bs);
                        oc->fifo_samples = sndbuf_getready(bs) / sndbuf_getalign(bs);
#endif
                        CHN_UNLOCK(chn);
                }
                break;

        case SNDCTL_DSP_HALT_OUTPUT:
        case SNDCTL_DSP_HALT_INPUT:
                chn = (cmd == SNDCTL_DSP_HALT_OUTPUT) ? wrch : rdch;
                if (chn == NULL)
                        ret = EINVAL;
                else {
                        CHN_LOCK(chn);
                        chn_abort(chn);
                        CHN_UNLOCK(chn);
                }
                break;

        case SNDCTL_DSP_LOW_WATER:
        /*
         * Set the number of bytes required to attract attention by
         * select/poll.
         */
                if (wrch != NULL) {
                        CHN_LOCK(wrch);
                        wrch->lw = (*arg_i > 1) ? *arg_i : 1;
                        CHN_UNLOCK(wrch);
                }
                if (rdch != NULL) {
                        CHN_LOCK(rdch);
                        rdch->lw = (*arg_i > 1) ? *arg_i : 1;
                        CHN_UNLOCK(rdch);
                }
                break;

        case SNDCTL_DSP_GETERROR:
        /*
         * OSSv4 docs:  "All errors and counters will automatically be
         * cleared to zeroes after the call so each call will return only
         * the errors that occurred after the previous invocation. ... The
         * play_underruns and rec_overrun fields are the only useful fields
         * returned by OSS 4.0."
         */
                {
                        audio_errinfo *ei = (audio_errinfo *)arg;

                        bzero((void *)ei, sizeof(*ei));

                        if (wrch != NULL) {
                                CHN_LOCK(wrch);
                                ei->play_underruns = wrch->xruns;
                                wrch->xruns = 0;
                                CHN_UNLOCK(wrch);
                        }
                        if (rdch != NULL) {
                                CHN_LOCK(rdch);
                                ei->rec_overruns = rdch->xruns;
                                rdch->xruns = 0;
                                CHN_UNLOCK(rdch);
                        }
                }
                break;

        case SNDCTL_DSP_SYNCGROUP:
                PCM_ACQUIRE_QUICK(d);
                ret = dsp_oss_syncgroup(wrch, rdch, (oss_syncgroup *)arg);
                PCM_RELEASE_QUICK(d);
                break;

        case SNDCTL_DSP_SYNCSTART:
                PCM_ACQUIRE_QUICK(d);
                ret = dsp_oss_syncstart(*arg_i);
                PCM_RELEASE_QUICK(d);
                break;

        case SNDCTL_DSP_POLICY:
                PCM_ACQUIRE_QUICK(d);
                ret = dsp_oss_policy(wrch, rdch, *arg_i);
                PCM_RELEASE_QUICK(d);
                break;

        case SNDCTL_DSP_COOKEDMODE:
                PCM_ACQUIRE_QUICK(d);
                if (!(dsp_get_flags(i_dev) & SD_F_BITPERFECT))
                        ret = dsp_oss_cookedmode(wrch, rdch, *arg_i);
                PCM_RELEASE_QUICK(d);
                break;
        case SNDCTL_DSP_GET_CHNORDER:
                PCM_ACQUIRE_QUICK(d);
                ret = dsp_oss_getchnorder(wrch, rdch, (unsigned long long *)arg);
                PCM_RELEASE_QUICK(d);
                break;
        case SNDCTL_DSP_SET_CHNORDER:
                PCM_ACQUIRE_QUICK(d);
                ret = dsp_oss_setchnorder(wrch, rdch, (unsigned long long *)arg);
                PCM_RELEASE_QUICK(d);
                break;
        case SNDCTL_DSP_GETCHANNELMASK:         /* XXX vlc */
                PCM_ACQUIRE_QUICK(d);
                ret = dsp_oss_getchannelmask(wrch, rdch, (int *)arg);
                PCM_RELEASE_QUICK(d);
                break;
        case SNDCTL_DSP_BIND_CHANNEL:           /* XXX what?!? */
                ret = EINVAL;
                break;
#ifdef  OSSV4_EXPERIMENT
        /*
         * XXX The following ioctls are not yet supported and just return
         * EINVAL.
         */
        case SNDCTL_DSP_GETOPEAKS:
        case SNDCTL_DSP_GETIPEAKS:
                chn = (cmd == SNDCTL_DSP_GETOPEAKS) ? wrch : rdch;
                if (chn == NULL)
                        ret = EINVAL;
                else {
                        oss_peaks_t *op = (oss_peaks_t *)arg;
                        int lpeak, rpeak;

                        CHN_LOCK(chn);
                        ret = chn_getpeaks(chn, &lpeak, &rpeak);
                        if (ret == -1)
                                ret = EINVAL;
                        else {
                                (*op)[0] = lpeak;
                                (*op)[1] = rpeak;
                        }
                        CHN_UNLOCK(chn);
                }
                break;

        /*
         * XXX Once implemented, revisit this for proper cv protection
         *     (if necessary).
         */
        case SNDCTL_GETLABEL:
                ret = dsp_oss_getlabel(wrch, rdch, (oss_label_t *)arg);
                break;
        case SNDCTL_SETLABEL:
                ret = dsp_oss_setlabel(wrch, rdch, (oss_label_t *)arg);
                break;
        case SNDCTL_GETSONG:
                ret = dsp_oss_getsong(wrch, rdch, (oss_longname_t *)arg);
                break;
        case SNDCTL_SETSONG:
                ret = dsp_oss_setsong(wrch, rdch, (oss_longname_t *)arg);
                break;
        case SNDCTL_SETNAME:
                ret = dsp_oss_setname(wrch, rdch, (oss_longname_t *)arg);
                break;
#if 0
        /**
         * @note The S/PDIF interface ioctls, @c SNDCTL_DSP_READCTL and
         * @c SNDCTL_DSP_WRITECTL have been omitted at the suggestion of
         * 4Front Technologies.
         */
        case SNDCTL_DSP_READCTL:
        case SNDCTL_DSP_WRITECTL:
                ret = EINVAL;
                break;
#endif  /* !0 (explicitly omitted ioctls) */

#endif  /* !OSSV4_EXPERIMENT */
        case SNDCTL_DSP_MAPINBUF:
        case SNDCTL_DSP_MAPOUTBUF:
        case SNDCTL_DSP_SETSYNCRO:
                /* undocumented */

        case SNDCTL_DSP_SUBDIVIDE:
        case SOUND_PCM_WRITE_FILTER:
        case SOUND_PCM_READ_FILTER:
                /* dunno what these do, don't sound important */

        default:
                DEB(kprintf("default ioctl fn 0x%08lx fail\n", cmd));
                ret = EINVAL;
                break;
        }

        PCM_GIANT_LEAVE(d);

        return (ret);
}

static struct filterops dsp_read_filtops =
        { FILTEROP_ISFD | FILTEROP_MPSAFE, NULL, dsp_filter_detach,
          dsp_filter_read };
static struct filterops dsp_write_filtops =
        { FILTEROP_ISFD | FILTEROP_MPSAFE, NULL, dsp_filter_detach,
          dsp_filter_write };

static int
/*dsp_poll(struct cdev *i_dev, int events, struct thread *td)*/
dsp_kqfilter(struct dev_kqfilter_args *ap)
{
        struct knote *kn = ap->a_kn;
        struct klist *klist;
        struct cdev *i_dev = ap->a_head.a_dev;
        struct snddev_info *d;
        struct pcm_channel *wrch, *rdch;
        struct snd_dbuf *bs = NULL;
        int ret;

        d = dsp_get_info(i_dev);
        if (!DSP_REGISTERED(d, i_dev))
                return (EBADF);

        PCM_GIANT_ENTER(d);

        wrch = NULL;
        rdch = NULL;
        ret = 0;

        getchns(i_dev, &rdch, &wrch, SD_F_PRIO_RD | SD_F_PRIO_WR);

        switch (kn->kn_filter) {
        case EVFILT_READ:
                if (rdch) {
                        kn->kn_fop = &dsp_read_filtops;
                        kn->kn_hook = (caddr_t)rdch;
                        bs = rdch->bufsoft;
                        ap->a_result = 0;
                } else {
                        ap->a_result = EINVAL;
                }
                break;
        case EVFILT_WRITE:
                if (wrch) {
                        kn->kn_fop = &dsp_write_filtops;
                        kn->kn_hook = (caddr_t)wrch;
                        bs = wrch->bufsoft;
                        ap->a_result = 0;
                } else {
                        ap->a_result = EINVAL;
                }
                break;
        default:
                ap->a_result = EOPNOTSUPP;
                break;
        }

        if (ap->a_result == 0) {
                klist = &sndbuf_getkq(bs)->ki_note;
                knote_insert(klist, kn);
        }

        relchns(i_dev, rdch, wrch, SD_F_PRIO_RD | SD_F_PRIO_WR);

        PCM_GIANT_LEAVE(d);

        return (ret);
}

static void
dsp_filter_detach(struct knote *kn)
{
        struct pcm_channel *ch = (struct pcm_channel *)kn->kn_hook;
        struct snd_dbuf *bs = ch->bufsoft;
        struct klist *klist;

        CHN_LOCK(ch);
        klist = &sndbuf_getkq(bs)->ki_note;
        knote_remove(klist, kn);
        CHN_UNLOCK(ch);
}

static int
dsp_filter_read(struct knote *kn, long hint)
{
        struct pcm_channel *rdch = (struct pcm_channel *)kn->kn_hook;
        struct thread *td = curthread;
        int ready;

        CHN_LOCK(rdch);
        ready = chn_poll(rdch, 1, td);
        CHN_UNLOCK(rdch);

        return (ready);
}

static int
dsp_filter_write(struct knote *kn, long hint)
{
        struct pcm_channel *wrch = (struct pcm_channel *)kn->kn_hook;
        struct thread *td = curthread;
        int ready;

        CHN_LOCK(wrch);
        ready = chn_poll(wrch, 1, td);
        CHN_UNLOCK(wrch);

        return (ready);
}

static int
dsp_mmap(struct dev_mmap_args *ap)
{
        vm_offset_t offset = ap->a_offset;

        ap->a_result = atop(vtophys(offset));
        return (0);
}

static int
dsp_mmap_single(struct dev_mmap_single_args *ap)
{
        struct cdev *i_dev = ap->a_head.a_dev;
        vm_ooffset_t *offset = ap->a_offset;
        vm_size_t size = ap->a_size;
        struct vm_object **object = ap->a_object;
        int nprot = ap->a_nprot;
        struct snddev_info *d;
        struct pcm_channel *wrch, *rdch, *c;

        /*
         * Reject PROT_EXEC by default. It just doesn't makes sense.
         * Unfortunately, we have to give up this one due to linux_mmap
         * changes.
         *
         * http://lists.freebsd.org/pipermail/freebsd-emulation/2007-June/003698.html
         *
         */
#ifdef SV_ABI_LINUX
        if ((nprot & PROT_EXEC) && (dsp_mmap_allow_prot_exec < 0 ||
            (dsp_mmap_allow_prot_exec == 0 &&
            SV_CURPROC_ABI() != SV_ABI_LINUX)))
#else
        if ((nprot & PROT_EXEC) && dsp_mmap_allow_prot_exec < 1)
#endif
                return (EINVAL);

        /*
         * PROT_READ (alone) selects the input buffer.
         * PROT_WRITE (alone) selects the output buffer.
         * PROT_WRITE|PROT_READ together select the output buffer.
         */
        if ((nprot & (PROT_READ | PROT_WRITE)) == 0)
                return (EINVAL);

        d = dsp_get_info(i_dev);
        if (!DSP_REGISTERED(d, i_dev))
                return (EINVAL);

        PCM_GIANT_ENTER(d);

        getchns(i_dev, &rdch, &wrch, SD_F_PRIO_RD | SD_F_PRIO_WR);

        c = ((nprot & PROT_WRITE) != 0) ? wrch : rdch;
        if (c == NULL || (c->flags & CHN_F_MMAP_INVALID) ||
            (*offset  + size) > sndbuf_getsize(c->bufsoft) ||
            (wrch != NULL && (wrch->flags & CHN_F_MMAP_INVALID)) ||
            (rdch != NULL && (rdch->flags & CHN_F_MMAP_INVALID))) {
                relchns(i_dev, rdch, wrch, SD_F_PRIO_RD | SD_F_PRIO_WR);
                PCM_GIANT_EXIT(d);
                return (EINVAL);
        }

        if (wrch != NULL)
                wrch->flags |= CHN_F_MMAP;
        if (rdch != NULL)
                rdch->flags |= CHN_F_MMAP;

        *offset = (uintptr_t)sndbuf_getbufofs(c->bufsoft, *offset);
        relchns(i_dev, rdch, wrch, SD_F_PRIO_RD | SD_F_PRIO_WR);
        *object = dev_pager_alloc(i_dev, size, nprot, *offset);

        PCM_GIANT_LEAVE(d);

        if (*object == NULL)
                 return (EINVAL);
        return (0);
}

/*
 * for i = 0 to channels of device N
 * if dspN.i isn't busy and in the right dir, create a dev_t and return it
 */
int
dsp_clone(struct dev_clone_args *ap)
{
        struct cdev *i_dev = ap->a_head.a_dev;
        struct snddev_info *d;
        struct snd_clone_entry *ce;
        struct pcm_channel *c;
        int i, unit, udcmask, cunit, devtype, devhw, devcmax, tumax;
        size_t len;
        char sname[64];
        int err = EBUSY;
        static struct cdev *dev = NULL;

        KASSERT(dsp_umax >= 0 && dsp_cmax >= 0, ("Uninitialized unit!"));

        /*
         * The default dsp device has a special unit which must be adjusted,
         * otherwise the unit number is already correct.
         */
        unit = PCMUNIT(i_dev);
        if (unit == PCMUNIT_DEFAULT)
                unit = snd_unit;

        ksnprintf(sname, sizeof(sname), "%s", ap->a_name);
        len = strlen(sname);
        while (len && sname[len-1] >= '0' && sname[len-1] <= '9')
                --len;
        sname[len] = 0;

        cunit = -1;
        devtype = -1;
        devhw = 0;
        devcmax = -1;
        tumax = -1;

        for (i = 0; i < sizeof(dsp_cdevs) / sizeof(dsp_cdevs[0]); ++i) {
                if (strcmp(dsp_cdevs[i].name, sname) != 0)
                        continue;
                devtype = dsp_cdevs[i].type;
                devhw = dsp_cdevs[i].hw;
                devcmax = dsp_cdevs[i].max - 1;
                break;
        }

        d = devclass_get_softc(pcm_devclass, unit);
        if (!PCM_REGISTERED(d) || d->clones == NULL) {
                return (ENODEV);
        }

        /* XXX Need Giant magic entry ??? */

        PCM_LOCK(d);
        if (snd_clone_disabled(d->clones)) {
                PCM_UNLOCK(d);
                return (ENODEV);
        }

        PCM_WAIT(d);
        PCM_ACQUIRE(d);
        PCM_UNLOCK(d);

        udcmask = snd_u2unit(unit) | snd_d2unit(devtype);

        if (devhw != 0) {
                KASSERT(devcmax <= dsp_cmax,
                    ("overflow: devcmax=%d, dsp_cmax=%d", devcmax, dsp_cmax));
                if (cunit > devcmax) {
                        PCM_RELEASE_QUICK(d);
                        return (ENODEV);
                }
                udcmask |= snd_c2unit(cunit);
                CHN_FOREACH(c, d, channels.pcm) {
                        CHN_LOCK(c);
                        if (c->unit != udcmask) {
                                CHN_UNLOCK(c);
                                continue;
                        }
                        CHN_UNLOCK(c);
                        udcmask &= ~snd_c2unit(cunit);
                        /*
                         * Temporarily increase clone maxunit to overcome
                         * vchan flexibility.
                         *
                         * # sysctl dev.pcm.0.play.vchans=256
                         * dev.pcm.0.play.vchans: 1 -> 256
                         * # cat /dev/zero > /dev/dsp0.vp255 &
                         * [1] 17296
                         * # sysctl dev.pcm.0.play.vchans=0
                         * dev.pcm.0.play.vchans: 256 -> 1
                         * # fg
                         * [1]  + running    cat /dev/zero > /dev/dsp0.vp255
                         * ^C
                         * # cat /dev/zero > /dev/dsp0.vp255
                         * zsh: operation not supported: /dev/dsp0.vp255
                         */
                        tumax = snd_clone_getmaxunit(d->clones);
                        if (cunit > tumax)
                                snd_clone_setmaxunit(d->clones, cunit);
                        else
                                tumax = -1;
                        goto dsp_clone_alloc;
                }
                /*
                 * Ok, so we're requesting unallocated vchan, but still
                 * within maximum vchan limit.
                 */
                if (((devtype == SND_DEV_DSPHW_VPLAY && d->pvchancount > 0) ||
                    (devtype == SND_DEV_DSPHW_VREC && d->rvchancount > 0)) &&
                    cunit < snd_maxautovchans) {
                        udcmask &= ~snd_c2unit(cunit);
                        tumax = snd_clone_getmaxunit(d->clones);
                        if (cunit > tumax)
                                snd_clone_setmaxunit(d->clones, cunit);
                        else
                                tumax = -1;
                        goto dsp_clone_alloc;
                }
                PCM_RELEASE_QUICK(d);
                return (err);
        }

        /*
         * Allocate channel, create device if necessary.
         */
dsp_clone_alloc:
        ce = snd_clone_alloc(d->clones, &dev, &cunit, udcmask);
        if (tumax != -1)
                snd_clone_setmaxunit(d->clones, tumax);
        if (ce != NULL) {
                /*
                 * NOTE: Subunit is a unique number unrelated to the
                 *       channel id.
                 */
                udcmask |= snd_c2unit(cunit);
                int subunit = devfs_clone_bitmap_get(&DEVFS_CLONE_BITMAP(dsp), 0);

                dev = make_only_dev(&dsp_ops,
                    PCMMKMINOR(unit, devtype, subunit),
                    UID_ROOT, GID_WHEEL, 0666, "%s%d.%d",
                    sname, unit, subunit);
                snd_clone_register(ce, dev);
                err = 0;
        } else {
                /*
                 * Use device already registered, we must add a ref to the
                 * device.
                 */
                err = 0;
        }

        ap->a_dev = dev;

        PCM_RELEASE_QUICK(d);

        return (err);
}

static void
dsp_sysinit(void *p)
{
        if (dsp_ehtag != NULL)
                return;
        /* initialize unit numbering */
        snd_unit_init();
        dsp_umax = PCMMAXUNIT;
        dsp_cmax = PCMMAXCHAN;
        dsp_ehtag = EVENTHANDLER_REGISTER(dev_clone, dsp_clone, 0, 1000);

        devfs_clone_bitmap_init(&DEVFS_CLONE_BITMAP(dsp));
}

static void
dsp_sysuninit(void *p)
{
        if (dsp_ehtag == NULL)
                return;
        EVENTHANDLER_DEREGISTER(dev_clone, dsp_ehtag);
        dsp_ehtag = NULL;
}

SYSINIT(dsp_sysinit, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, dsp_sysinit, NULL);
SYSUNINIT(dsp_sysuninit, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, dsp_sysuninit, NULL);

char *
dsp_unit2name(char *buf, size_t len, int unit)
{
        int i, dtype;

        KASSERT(buf != NULL && len != 0,
            ("bogus buf=%p len=%ju", buf, (uintmax_t)len));

        dtype = snd_unit2d(unit);

        for (i = 0; i < (sizeof(dsp_cdevs) / sizeof(dsp_cdevs[0])); i++) {
                if (dtype != dsp_cdevs[i].type || dsp_cdevs[i].alias != NULL)
                        continue;
                ksnprintf(buf, len, "%s%d%s%d", dsp_cdevs[i].name,
                    snd_unit2u(unit), dsp_cdevs[i].sep, snd_unit2c(unit));
                return (buf);
        }

        return (NULL);
}

/**
 * @brief Handler for SNDCTL_AUDIOINFO.
 *
 * Gathers information about the audio device specified in ai->dev.  If
 * ai->dev == -1, then this function gathers information about the current
 * device.  If the call comes in on a non-audio device and ai->dev == -1,
 * return EINVAL.
 *
 * This routine is supposed to go practically straight to the hardware,
 * getting capabilities directly from the sound card driver, side-stepping
 * the intermediate channel interface.
 *
 * Note, however, that the usefulness of this command is significantly
 * decreased when requesting info about any device other than the one serving
 * the request. While each snddev_channel refers to a specific device node,
 * the converse is *not* true.  Currently, when a sound device node is opened,
 * the sound subsystem scans for an available audio channel (or channels, if
 * opened in read+write) and then assigns them to the si_drv[12] private
 * data fields.  As a result, any information returned linking a channel to
 * a specific character device isn't necessarily accurate.
 *
 * @note
 * Calling threads must not hold any snddev_info or pcm_channel locks.
 * 
 * @param dev           device on which the ioctl was issued
 * @param ai            ioctl request data container
 *
 * @retval 0            success
 * @retval EINVAL       ai->dev specifies an invalid device
 *
 * @todo Verify correctness of Doxygen tags.  ;)
 */
int
dsp_oss_audioinfo(struct cdev *i_dev, oss_audioinfo *ai)
{
        struct pcmchan_caps *caps;
        struct pcm_channel *ch;
        struct snddev_info *d;
        uint32_t fmts;
        int i, nchan, *rates, minch, maxch;
        char *devname, buf[CHN_NAMELEN];

        /*
         * If probing the device that received the ioctl, make sure it's a
         * DSP device.  (Users may use this ioctl with /dev/mixer and
         * /dev/midi.)
         */
        if (ai->dev == -1 && i_dev->si_ops != &dsp_ops)
                return (EINVAL);

        ch = NULL;
        devname = NULL;
        nchan = 0;
        bzero(buf, sizeof(buf));

        /*
         * Search for the requested audio device (channel).  Start by
         * iterating over pcm devices.
         */ 
        for (i = 0; pcm_devclass != NULL &&
            i < devclass_get_maxunit(pcm_devclass); i++) {
                d = devclass_get_softc(pcm_devclass, i);
                if (!PCM_REGISTERED(d))
                        continue;

                /* XXX Need Giant magic entry ??? */

                /* See the note in function docblock */
                PCM_UNLOCKASSERT(d);
                PCM_LOCK(d);

                CHN_FOREACH(ch, d, channels.pcm) {
                        CHN_UNLOCKASSERT(ch);
                        CHN_LOCK(ch);
                        if (ai->dev == -1) {
                                if (DSP_REGISTERED(d, i_dev) &&
                                    (ch == PCM_RDCH(i_dev) ||   /* record ch */
                                    ch == PCM_WRCH(i_dev))) {   /* playback ch */
                                        devname = dsp_unit2name(buf,
                                            sizeof(buf), ch->unit);
                                }
                        } else if (ai->dev == nchan) {
                                devname = dsp_unit2name(buf, sizeof(buf),
                                    ch->unit);
                        }
                        if (devname != NULL)
                                break;
                        CHN_UNLOCK(ch);
                        ++nchan;
                }

                if (devname != NULL) {
                        /*
                         * At this point, the following synchronization stuff
                         * has happened:
                         * - a specific PCM device is locked.
                         * - a specific audio channel has been locked, so be
                         *   sure to unlock when exiting;
                         */

                        caps = chn_getcaps(ch);

                        /*
                         * With all handles collected, zero out the user's
                         * container and begin filling in its fields.
                         */
                        bzero((void *)ai, sizeof(oss_audioinfo));

                        ai->dev = nchan;
                        strlcpy(ai->name, ch->name,  sizeof(ai->name));

                        if ((ch->flags & CHN_F_BUSY) == 0)
                                ai->busy = 0;
                        else
                                ai->busy = (ch->direction == PCMDIR_PLAY) ? OPEN_WRITE : OPEN_READ;

                        /**
                         * @note
                         * @c cmd - OSSv4 docs: "Only supported under Linux at
                         *    this moment." Cop-out, I know, but I'll save
                         *    running around in the process table for later.
                         *    Is there a risk of leaking information?
                         */
                        ai->pid = ch->pid;

                        /*
                         * These flags stolen from SNDCTL_DSP_GETCAPS handler.
                         * Note, however, that a single channel operates in
                         * only one direction, so PCM_CAP_DUPLEX is out.
                         */
                        /**
                         * @todo @c SNDCTL_AUDIOINFO::caps - Make drivers keep
                         *       these in pcmchan::caps?
                         */
                        ai->caps = PCM_CAP_REALTIME | PCM_CAP_MMAP | PCM_CAP_TRIGGER |
                            ((ch->direction == PCMDIR_PLAY) ? PCM_CAP_OUTPUT : PCM_CAP_INPUT);

                        /*
                         * Collect formats supported @b natively by the
                         * device.  Also determine min/max channels.  (I.e.,
                         * mono, stereo, or both?)
                         *
                         * If any channel is stereo, maxch = 2;
                         * if all channels are stereo, minch = 2, too;
                         * if any channel is mono, minch = 1;
                         * and if all channels are mono, maxch = 1.
                         */
                        minch = 0;
                        maxch = 0;
                        fmts = 0;
                        for (i = 0; caps->fmtlist[i]; i++) {
                                fmts |= caps->fmtlist[i];
                                if (AFMT_CHANNEL(caps->fmtlist[i]) > 1) {
                                        minch = (minch == 0) ? 2 : minch;
                                        maxch = 2;
                                } else {
                                        minch = 1;
                                        maxch = (maxch == 0) ? 1 : maxch;
                                }
                        }

                        if (ch->direction == PCMDIR_PLAY)
                                ai->oformats = fmts;
                        else
                                ai->iformats = fmts;

                        /**
                         * @note
                         * @c magic - OSSv4 docs: "Reserved for internal use
                         *    by OSS."
                         *
                         * @par
                         * @c card_number - OSSv4 docs: "Number of the sound
                         *    card where this device belongs or -1 if this
                         *    information is not available.  Applications
                         *    should normally not use this field for any
                         *    purpose."
                         */
                        ai->card_number = -1;
                        /**
                         * @todo @c song_name - depends first on
                         *          SNDCTL_[GS]ETSONG @todo @c label - depends
                         *          on SNDCTL_[GS]ETLABEL
                         * @todo @c port_number - routing information?
                         */
                        ai->port_number = -1;
                        ai->mixer_dev = (d->mixer_dev != NULL) ? PCMUNIT(d->mixer_dev) : -1;
                        /**
                         * @note
                         * @c real_device - OSSv4 docs:  "Obsolete."
                         */
                        ai->real_device = -1;
                        strlcpy(ai->devnode, "/dev/", sizeof(ai->devnode));
                        strlcat(ai->devnode, devname, sizeof(ai->devnode));
                        ai->enabled = device_is_attached(d->dev) ? 1 : 0;
                        /**
                         * @note
                         * @c flags - OSSv4 docs: "Reserved for future use."
                         *
                         * @note
                         * @c binding - OSSv4 docs: "Reserved for future use."
                         *
                         * @todo @c handle - haven't decided how to generate
                         *       this yet; bus, vendor, device IDs?
                         */
                        ai->min_rate = caps->minspeed;
                        ai->max_rate = caps->maxspeed;

                        ai->min_channels = minch;
                        ai->max_channels = maxch;

                        ai->nrates = chn_getrates(ch, &rates);
                        if (ai->nrates > OSS_MAX_SAMPLE_RATES)
                                ai->nrates = OSS_MAX_SAMPLE_RATES;

                        for (i = 0; i < ai->nrates; i++)
                                ai->rates[i] = rates[i];
                        
                        ai->next_play_engine = 0;
                        ai->next_rec_engine = 0;

                        CHN_UNLOCK(ch);
                }

                PCM_UNLOCK(d);

                if (devname != NULL)
                        return (0);
        }

        /* Exhausted the search -- nothing is locked, so return. */
        return (EINVAL);
}

/**
 * @brief Assigns a PCM channel to a sync group.
 *
 * Sync groups are used to enable audio operations on multiple devices
 * simultaneously.  They may be used with any number of devices and may
 * span across applications.  Devices are added to groups with
 * the SNDCTL_DSP_SYNCGROUP ioctl, and operations are triggered with the
 * SNDCTL_DSP_SYNCSTART ioctl.
 *
 * If the @c id field of the @c group parameter is set to zero, then a new
 * sync group is created.  Otherwise, wrch and rdch (if set) are added to
 * the group specified.
 *
 * @todo As far as memory allocation, should we assume that things are
 *       okay and allocate with M_WAITOK before acquiring channel locks,
 *       freeing later if not?
 *
 * @param wrch  output channel associated w/ device (if any)
 * @param rdch  input channel associated w/ device (if any)
 * @param group Sync group parameters
 *
 * @retval 0            success
 * @retval non-zero     error to be propagated upstream
 */
static int
dsp_oss_syncgroup(struct pcm_channel *wrch, struct pcm_channel *rdch, oss_syncgroup *group)
{
        struct pcmchan_syncmember *smrd, *smwr;
        struct pcmchan_syncgroup *sg;
        int ret, sg_ids[3];

        smrd = NULL;
        smwr = NULL;
        sg = NULL;
        ret = 0;

        /*
         * Free_unr() may sleep, so store released syncgroup IDs until after
         * all locks are released.
         */
        sg_ids[0] = sg_ids[1] = sg_ids[2] = 0;

        PCM_SG_LOCK();

        /*
         * - Insert channel(s) into group's member list.
         * - Set CHN_F_NOTRIGGER on channel(s).
         * - Stop channel(s).  
         */

        /*
         * If device's channels are already mapped to a group, unmap them.
         */
        if (wrch) {
                CHN_LOCK(wrch);
                sg_ids[0] = chn_syncdestroy(wrch);
        }

        if (rdch) {
                CHN_LOCK(rdch);
                sg_ids[1] = chn_syncdestroy(rdch);
        }

        /*
         * Verify that mode matches character device properites.
         *  - Bail if PCM_ENABLE_OUTPUT && wrch == NULL.
         *  - Bail if PCM_ENABLE_INPUT && rdch == NULL.
         */
        if (((wrch == NULL) && (group->mode & PCM_ENABLE_OUTPUT)) ||
            ((rdch == NULL) && (group->mode & PCM_ENABLE_INPUT))) {
                ret = EINVAL;
                goto out;
        }

        /*
         * An id of zero indicates the user wants to create a new
         * syncgroup.
         */
        if (group->id == 0) {
                sg = (struct pcmchan_syncgroup *)kmalloc(sizeof(*sg), M_DEVBUF, M_WAITOK | M_ZERO);
                if (sg != NULL) {
                        SLIST_INIT(&sg->members);
                        sg->id = alloc_unr(pcmsg_unrhdr);

                        group->id = sg->id;
                        SLIST_INSERT_HEAD(&snd_pcm_syncgroups, sg, link);
                } else
                        ret = ENOMEM;
        } else {
                SLIST_FOREACH(sg, &snd_pcm_syncgroups, link) {
                        if (sg->id == group->id)
                                break;
                }
                if (sg == NULL)
                        ret = EINVAL;
        }

        /* Couldn't create or find a syncgroup.  Fail. */
        if (sg == NULL)
                goto out;

        /*
         * Allocate a syncmember, assign it and a channel together, and
         * insert into syncgroup.
         */
        if (group->mode & PCM_ENABLE_INPUT) {
                smrd = (struct pcmchan_syncmember *)kmalloc(sizeof(*smrd), M_DEVBUF, M_WAITOK | M_ZERO);
                if (smrd == NULL) {
                        ret = ENOMEM;
                        goto out;
                }

                SLIST_INSERT_HEAD(&sg->members, smrd, link);
                smrd->parent = sg;
                smrd->ch = rdch;

                chn_abort(rdch);
                rdch->flags |= CHN_F_NOTRIGGER;
                rdch->sm = smrd;
        }

        if (group->mode & PCM_ENABLE_OUTPUT) {
                smwr = (struct pcmchan_syncmember *)kmalloc(sizeof(*smwr), M_DEVBUF, M_WAITOK | M_ZERO);
                if (smwr == NULL) {
                        ret = ENOMEM;
                        goto out;
                }

                SLIST_INSERT_HEAD(&sg->members, smwr, link);
                smwr->parent = sg;
                smwr->ch = wrch;

                chn_abort(wrch);
                wrch->flags |= CHN_F_NOTRIGGER;
                wrch->sm = smwr;
        }


out:
        if (ret != 0) {
                if (smrd != NULL)
                        kfree(smrd, M_DEVBUF);
                if ((sg != NULL) && SLIST_EMPTY(&sg->members)) {
                        sg_ids[2] = sg->id;
                        SLIST_REMOVE(&snd_pcm_syncgroups, sg, pcmchan_syncgroup, link);
                        kfree(sg, M_DEVBUF);
                }

                if (wrch)
                        wrch->sm = NULL;
                if (rdch)
                        rdch->sm = NULL;
        }

        if (wrch)
                CHN_UNLOCK(wrch);
        if (rdch)
                CHN_UNLOCK(rdch);

        PCM_SG_UNLOCK();

        if (sg_ids[0])
                free_unr(pcmsg_unrhdr, sg_ids[0]);
        if (sg_ids[1])
                free_unr(pcmsg_unrhdr, sg_ids[1]);
        if (sg_ids[2])
                free_unr(pcmsg_unrhdr, sg_ids[2]);

        return (ret);
}

/**
 * @brief Launch a sync group into action
 *
 * Sync groups are established via SNDCTL_DSP_SYNCGROUP.  This function
 * iterates over all members, triggering them along the way.
 *
 * @note Caller must not hold any channel locks.
 *
 * @param sg_id sync group identifier
 *
 * @retval 0    success
 * @retval non-zero     error worthy of propagating upstream to user
 */
static int
dsp_oss_syncstart(int sg_id)
{
        struct pcmchan_syncmember *sm, *sm_tmp;
        struct pcmchan_syncgroup *sg;
        struct pcm_channel *c;
        int ret, needlocks;

        /* Get the synclists lock */
        PCM_SG_LOCK();

        do {
                ret = 0;
                needlocks = 0;

                /* Search for syncgroup by ID */
                SLIST_FOREACH(sg, &snd_pcm_syncgroups, link) {
                        if (sg->id == sg_id)
                                break;
                }

                /* Return EINVAL if not found */
                if (sg == NULL) {
                        ret = EINVAL;
                        break;
                }

                /* Any removals resulting in an empty group should've handled this */
                KASSERT(!SLIST_EMPTY(&sg->members), ("found empty syncgroup"));

                /*
                 * Attempt to lock all member channels - if any are already
                 * locked, unlock those acquired, sleep for a bit, and try
                 * again.
                 */
                SLIST_FOREACH(sm, &sg->members, link) {
                        if (CHN_TRYLOCK(sm->ch) == 0) {
                                int timo = hz * 5/1000; 
                                if (timo < 1)
                                        timo = 1;

                                /* Release all locked channels so far, retry */
                                SLIST_FOREACH(sm_tmp, &sg->members, link) {
                                        /* sm is the member already locked */
                                        if (sm == sm_tmp)
                                                break;
                                        CHN_UNLOCK(sm_tmp->ch);
                                }

                                /** @todo Is PRIBIO correct/ */
                                ret = lksleep(sm, &snd_pcm_syncgroups_mtx,
                                    PCATCH, "pcmsg", timo);
                                if (ret == EINTR || ret == ERESTART)
                                        break;

                                needlocks = 1;
                                ret = 0; /* Assumes ret == EAGAIN... */
                        }
                }
        } while (needlocks && ret == 0);

        /* Proceed only if no errors encountered. */
        if (ret == 0) {
                /* Launch channels */
                while ((sm = SLIST_FIRST(&sg->members)) != NULL) {
                        SLIST_REMOVE_HEAD(&sg->members, link);

                        c = sm->ch;
                        c->sm = NULL;
                        chn_start(c, 1);
                        c->flags &= ~CHN_F_NOTRIGGER;
                        CHN_UNLOCK(c);

                        kfree(sm, M_DEVBUF);
                }

                SLIST_REMOVE(&snd_pcm_syncgroups, sg, pcmchan_syncgroup, link);
                kfree(sg, M_DEVBUF);
        }

        PCM_SG_UNLOCK();

        /*
         * Free_unr() may sleep, so be sure to give up the syncgroup lock
         * first.
         */
        if (ret == 0)
                free_unr(pcmsg_unrhdr, sg_id);

        return (ret);
}

/**
 * @brief Handler for SNDCTL_DSP_POLICY
 *
 * The SNDCTL_DSP_POLICY ioctl is a simpler interface to control fragment
 * size and count like with SNDCTL_DSP_SETFRAGMENT.  Instead of the user
 * specifying those two parameters, s/he simply selects a number from 0..10
 * which corresponds to a buffer size.  Smaller numbers request smaller
 * buffers with lower latencies (at greater overhead from more frequent
 * interrupts), while greater numbers behave in the opposite manner.
 *
 * The 4Front spec states that a value of 5 should be the default.  However,
 * this implementation deviates slightly by using a linear scale without
 * consulting drivers.  I.e., even though drivers may have different default
 * buffer sizes, a policy argument of 5 will have the same result across
 * all drivers.
 *
 * See http://manuals.opensound.com/developer/SNDCTL_DSP_POLICY.html for
 * more information.
 *
 * @todo When SNDCTL_DSP_COOKEDMODE is supported, it'll be necessary to
 *       work with hardware drivers directly.
 *
 * @note PCM channel arguments must not be locked by caller.
 *
 * @param wrch  Pointer to opened playback channel (optional; may be NULL)
 * @param rdch  " recording channel (optional; may be NULL)
 * @param policy Integer from [0:10]
 *
 * @retval 0    constant (for now)
 */
static int
dsp_oss_policy(struct pcm_channel *wrch, struct pcm_channel *rdch, int policy)
{
        int ret;

        if (policy < CHN_POLICY_MIN || policy > CHN_POLICY_MAX)
                return (EIO);

        /* Default: success */
        ret = 0;

        if (rdch) {
                CHN_LOCK(rdch);
                ret = chn_setlatency(rdch, policy);
                CHN_UNLOCK(rdch);
        }

        if (wrch && ret == 0) {
                CHN_LOCK(wrch);
                ret = chn_setlatency(wrch, policy);
                CHN_UNLOCK(wrch);
        }

        if (ret)
                ret = EIO;

        return (ret);
}

/**
 * @brief Enable or disable "cooked" mode
 *
 * This is a handler for @c SNDCTL_DSP_COOKEDMODE.  When in cooked mode, which
 * is the default, the sound system handles rate and format conversions
 * automatically (ex: user writing 11025Hz/8 bit/unsigned but card only
 * operates with 44100Hz/16bit/signed samples).
 *
 * Disabling cooked mode is intended for applications wanting to mmap()
 * a sound card's buffer space directly, bypassing the FreeBSD 2-stage
 * feeder architecture, presumably to gain as much control over audio
 * hardware as possible.
 *
 * See @c http://manuals.opensound.com/developer/SNDCTL_DSP_COOKEDMODE.html
 * for more details.
 *
 * @param wrch          playback channel (optional; may be NULL)
 * @param rdch          recording channel (optional; may be NULL)
 * @param enabled       0 = raw mode, 1 = cooked mode
 *
 * @retval EINVAL       Operation not yet supported.
 */
static int
dsp_oss_cookedmode(struct pcm_channel *wrch, struct pcm_channel *rdch, int enabled)
{

        /*
         * XXX I just don't get it. Why don't they call it
         * "BITPERFECT" ~ SNDCTL_DSP_BITPERFECT !?!?.
         * This is just plain so confusing, incoherent,
         * <insert any non-printable characters here>.
         */
        if (!(enabled == 1 || enabled == 0))
                return (EINVAL);

        /*
         * I won't give in. I'm inverting its logic here and now.
         * Brag all you want, but "BITPERFECT" should be the better
         * term here.
         */
        enabled ^= 0x00000001;

        if (wrch != NULL) {
                CHN_LOCK(wrch);
                wrch->flags &= ~CHN_F_BITPERFECT;
                wrch->flags |= (enabled != 0) ? CHN_F_BITPERFECT : 0x00000000;
                CHN_UNLOCK(wrch);
        }

        if (rdch != NULL) {
                CHN_LOCK(rdch);
                rdch->flags &= ~CHN_F_BITPERFECT;
                rdch->flags |= (enabled != 0) ? CHN_F_BITPERFECT : 0x00000000;
                CHN_UNLOCK(rdch);
        }

        return (0);
}

/**
 * @brief Retrieve channel interleaving order
 *
 * This is the handler for @c SNDCTL_DSP_GET_CHNORDER.
 *
 * See @c http://manuals.opensound.com/developer/SNDCTL_DSP_GET_CHNORDER.html
 * for more details.
 *
 * @note As the ioctl definition is still under construction, FreeBSD
 *       does not currently support SNDCTL_DSP_GET_CHNORDER.
 *
 * @param wrch  playback channel (optional; may be NULL)
 * @param rdch  recording channel (optional; may be NULL)
 * @param map   channel map (result will be stored there)
 *
 * @retval EINVAL       Operation not yet supported.
 */
static int
dsp_oss_getchnorder(struct pcm_channel *wrch, struct pcm_channel *rdch, unsigned long long *map)
{
        struct pcm_channel *ch;
        int ret;

        ch = (wrch != NULL) ? wrch : rdch;
        if (ch != NULL) {
                CHN_LOCK(ch);
                ret = chn_oss_getorder(ch, map);
                CHN_UNLOCK(ch);
        } else
                ret = EINVAL;

        return (ret);
}

/**
 * @brief Specify channel interleaving order
 *
 * This is the handler for @c SNDCTL_DSP_SET_CHNORDER.
 *
 * @note As the ioctl definition is still under construction, FreeBSD
 *       does not currently support @c SNDCTL_DSP_SET_CHNORDER.
 *
 * @param wrch  playback channel (optional; may be NULL)
 * @param rdch  recording channel (optional; may be NULL)
 * @param map   channel map
 *
 * @retval EINVAL       Operation not yet supported.
 */
static int
dsp_oss_setchnorder(struct pcm_channel *wrch, struct pcm_channel *rdch, unsigned long long *map)
{
        int ret;

        ret = 0;

        if (wrch != NULL) {
                CHN_LOCK(wrch);
                ret = chn_oss_setorder(wrch, map);
                CHN_UNLOCK(wrch);
        }

        if (ret == 0 && rdch != NULL) {
                CHN_LOCK(rdch);
                ret = chn_oss_setorder(rdch, map);
                CHN_UNLOCK(rdch);
        }

        return (ret);
}

static int
dsp_oss_getchannelmask(struct pcm_channel *wrch, struct pcm_channel *rdch,
    int *mask)
{
        struct pcm_channel *ch;
        uint32_t chnmask;
        int ret;

        chnmask = 0;
        ch = (wrch != NULL) ? wrch : rdch;

        if (ch != NULL) {
                CHN_LOCK(ch);
                ret = chn_oss_getmask(ch, &chnmask);
                CHN_UNLOCK(ch);
        } else
                ret = EINVAL;

        if (ret == 0)
                *mask = chnmask;

        return (ret);
}

#ifdef OSSV4_EXPERIMENT
/**
 * @brief Retrieve an audio device's label
 *
 * This is a handler for the @c SNDCTL_GETLABEL ioctl.
 *
 * See @c http://manuals.opensound.com/developer/SNDCTL_GETLABEL.html
 * for more details.
 *
 * From Hannu@4Front:  "For example ossxmix (just like some HW mixer
 * consoles) can show variable "labels" for certain controls. By default
 * the application name (say quake) is shown as the label but
 * applications may change the labels themselves."
 *
 * @note As the ioctl definition is still under construction, FreeBSD
 *       does not currently support @c SNDCTL_GETLABEL.
 *
 * @param wrch  playback channel (optional; may be NULL)
 * @param rdch  recording channel (optional; may be NULL)
 * @param label label gets copied here
 *
 * @retval EINVAL       Operation not yet supported.
 */
static int
dsp_oss_getlabel(struct pcm_channel *wrch, struct pcm_channel *rdch, oss_label_t *label)
{
        return (EINVAL);
}

/**
 * @brief Specify an audio device's label
 *
 * This is a handler for the @c SNDCTL_SETLABEL ioctl.  Please see the
 * comments for @c dsp_oss_getlabel immediately above.
 *
 * See @c http://manuals.opensound.com/developer/SNDCTL_GETLABEL.html
 * for more details.
 *
 * @note As the ioctl definition is still under construction, FreeBSD
 *       does not currently support SNDCTL_SETLABEL.
 *
 * @param wrch  playback channel (optional; may be NULL)
 * @param rdch  recording channel (optional; may be NULL)
 * @param label label gets copied from here
 *
 * @retval EINVAL       Operation not yet supported.
 */
static int
dsp_oss_setlabel(struct pcm_channel *wrch, struct pcm_channel *rdch, oss_label_t *label)
{
        return (EINVAL);
}

/**
 * @brief Retrieve name of currently played song
 *
 * This is a handler for the @c SNDCTL_GETSONG ioctl.  Audio players could
 * tell the system the name of the currently playing song, which would be
 * visible in @c /dev/sndstat.
 *
 * See @c http://manuals.opensound.com/developer/SNDCTL_GETSONG.html
 * for more details.
 *
 * @note As the ioctl definition is still under construction, FreeBSD
 *       does not currently support SNDCTL_GETSONG.
 *
 * @param wrch  playback channel (optional; may be NULL)
 * @param rdch  recording channel (optional; may be NULL)
 * @param song  song name gets copied here
 *
 * @retval EINVAL       Operation not yet supported.
 */
static int
dsp_oss_getsong(struct pcm_channel *wrch, struct pcm_channel *rdch, oss_longname_t *song)
{
        return (EINVAL);
}

/**
 * @brief Retrieve name of currently played song
 *
 * This is a handler for the @c SNDCTL_SETSONG ioctl.  Audio players could
 * tell the system the name of the currently playing song, which would be
 * visible in @c /dev/sndstat.
 *
 * See @c http://manuals.opensound.com/developer/SNDCTL_SETSONG.html
 * for more details.
 *
 * @note As the ioctl definition is still under construction, FreeBSD
 *       does not currently support SNDCTL_SETSONG.
 *
 * @param wrch  playback channel (optional; may be NULL)
 * @param rdch  recording channel (optional; may be NULL)
 * @param song  song name gets copied from here
 *
 * @retval EINVAL       Operation not yet supported.
 */
static int
dsp_oss_setsong(struct pcm_channel *wrch, struct pcm_channel *rdch, oss_longname_t *song)
{
        return (EINVAL);
}

/**
 * @brief Rename a device
 *
 * This is a handler for the @c SNDCTL_SETNAME ioctl.
 *
 * See @c http://manuals.opensound.com/developer/SNDCTL_SETNAME.html for
 * more details.
 *
 * From Hannu@4Front:  "This call is used to change the device name
 * reported in /dev/sndstat and ossinfo. So instead of  using some generic
 * 'OSS loopback audio (MIDI) driver' the device may be given a meaningfull
 * name depending on the current context (for example 'OSS virtual wave table
 * synth' or 'VoIP link to London')."
 *
 * @note As the ioctl definition is still under construction, FreeBSD
 *       does not currently support SNDCTL_SETNAME.
 *
 * @param wrch  playback channel (optional; may be NULL)
 * @param rdch  recording channel (optional; may be NULL)
 * @param name  new device name gets copied from here
 *
 * @retval EINVAL       Operation not yet supported.
 */
static int
dsp_oss_setname(struct pcm_channel *wrch, struct pcm_channel *rdch, oss_longname_t *name)
{
        return (EINVAL);
}
#endif  /* !OSSV4_EXPERIMENT */