/*      $NetBSD: dmover_io.c,v 1.46 2019/02/10 17:13:33 christos Exp $  */

/*
 * Copyright (c) 2002, 2003 Wasabi Systems, Inc.
 * All rights reserved.
 *
 * Written by Jason R. Thorpe for Wasabi Systems, Inc.
 *
 * 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed for the NetBSD Project by
 *      Wasabi Systems, Inc.
 * 4. The name of Wasabi Systems, Inc. may not be used to endorse
 *    or promote products derived from this software without specific prior
 *    written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``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 WASABI SYSTEMS, INC
 * 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.
 */

/*
 * dmover_io.c: Support for user-space access to dmover-api
 *
 * This interface is quite simple:
 *
 *      1.  The user opens /dev/dmover, which is a cloning device.  This
 *          allocates internal state for the session.
 *
 *      2.  The user does a DMIO_SETFUNC to select the data movement
 *          function.  This actually creates the dmover session.
 *
 *      3.  The user writes request messages to its dmover handle.
 *
 *      4.  The user reads request responses from its dmover handle.
 *
 *      5.  The user closes the file descriptor and the session is
 *          torn down.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: dmover_io.c,v 1.46 2019/02/10 17:13:33 christos Exp $");

#include <sys/param.h>
#include <sys/queue.h>
#include <sys/conf.h>
#include <sys/pool.h>
#include <sys/proc.h>
#include <sys/poll.h>
#include <sys/malloc.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/filio.h>
#include <sys/select.h>
#include <sys/systm.h>
#include <sys/workqueue.h>
#include <sys/once.h>
#include <sys/stat.h>
#include <sys/kauth.h>
#include <sys/mutex.h>
#include <sys/condvar.h>

#include <uvm/uvm_extern.h>

#include <dev/dmover/dmovervar.h>
#include <dev/dmover/dmover_io.h>

#include "ioconf.h"

struct dmio_usrreq_state {
        union {
                struct work u_work;
                TAILQ_ENTRY(dmio_usrreq_state) u_q;
        } dus_u;
#define dus_q           dus_u.u_q
#define dus_work        dus_u.u_work
        struct uio dus_uio_out;
        struct uio *dus_uio_in;
        struct dmover_request *dus_req;
        uint32_t dus_id;
        struct vmspace *dus_vmspace;
};

struct dmio_state {
        struct dmover_session *ds_session;
        TAILQ_HEAD(, dmio_usrreq_state) ds_pending;
        TAILQ_HEAD(, dmio_usrreq_state) ds_complete;
        struct selinfo ds_selq;
        volatile int ds_flags;
        u_int ds_nreqs;
        kmutex_t ds_lock;
        kcondvar_t ds_complete_cv;
        kcondvar_t ds_nreqs_cv;
        struct timespec ds_atime;
        struct timespec ds_mtime;
        struct timespec ds_btime;
};

static ONCE_DECL(dmio_cleaner_control);
static struct workqueue *dmio_cleaner;
static int dmio_cleaner_init(void);
static struct dmio_state *dmio_state_get(void);
static void dmio_state_put(struct dmio_state *);
static void dmio_usrreq_fini1(struct work *wk, void *);

#define DMIO_STATE_SEL          0x0001
#define DMIO_STATE_DEAD         0x0002
#define DMIO_STATE_LARVAL       0x0004
#define DMIO_STATE_READ_WAIT    0x0008
#define DMIO_STATE_WRITE_WAIT   0x0010

#define DMIO_NREQS_MAX          64      /* XXX pulled out of a hat */

struct pool dmio_state_pool;
struct pool dmio_usrreq_state_pool;

dev_type_open(dmoverioopen);

const struct cdevsw dmoverio_cdevsw = {
        .d_open = dmoverioopen,
        .d_close = noclose,
        .d_read = noread,
        .d_write = nowrite,
        .d_ioctl = noioctl,
        .d_stop = nostop,
        .d_tty = notty,
        .d_poll = nopoll,
        .d_mmap = nommap,
        .d_kqfilter = nokqfilter,
        .d_discard = nodiscard,
        .d_flag = D_OTHER
};

/*
 * dmoverioattach:
 *
 *      Pseudo-device attach routine.
 */
void
dmoverioattach(int count)
{

        pool_init(&dmio_state_pool, sizeof(struct dmio_state),
            0, 0, 0, "dmiostate", NULL, IPL_SOFTCLOCK);
        pool_init(&dmio_usrreq_state_pool, sizeof(struct dmio_usrreq_state),
            0, 0, 0, "dmiourstate", NULL, IPL_SOFTCLOCK);
}

/*
 * dmio_cleaner_init:
 *
 *      Create cleaner thread.
 */
static int
dmio_cleaner_init(void)
{

        return workqueue_create(&dmio_cleaner, "dmioclean", dmio_usrreq_fini1,
            NULL, PWAIT, IPL_SOFTCLOCK, 0);
}

static struct dmio_state *
dmio_state_get(void)
{
        struct dmio_state *ds;

        ds = pool_get(&dmio_state_pool, PR_WAITOK | PR_ZERO);

        getnanotime(&ds->ds_btime);
        ds->ds_atime = ds->ds_mtime = ds->ds_btime;

        mutex_init(&ds->ds_lock, MUTEX_DEFAULT, IPL_SOFTCLOCK);
        cv_init(&ds->ds_complete_cv, "dmvrrd");
        cv_init(&ds->ds_nreqs_cv, "dmiowr");
        TAILQ_INIT(&ds->ds_pending);
        TAILQ_INIT(&ds->ds_complete);
        selinit(&ds->ds_selq);

        return ds;
}

static void
dmio_state_put(struct dmio_state *ds)
{

        seldestroy(&ds->ds_selq);
        cv_destroy(&ds->ds_nreqs_cv);
        cv_destroy(&ds->ds_complete_cv);
        mutex_destroy(&ds->ds_lock);

        pool_put(&dmio_state_pool, ds);
}

/*
 * dmio_usrreq_init:
 *
 *      Build a request structure.
 */
static int
dmio_usrreq_init(struct file *fp, struct dmio_usrreq_state *dus,
    struct dmio_usrreq *req, struct dmover_request *dreq)
{
        struct dmio_state *ds = (struct dmio_state *) fp->f_data;
        struct dmover_session *dses = ds->ds_session;
        struct uio *uio_out = &dus->dus_uio_out;
        struct uio *uio_in;
        dmio_buffer inbuf;
        size_t len;
        int i, error;
        u_int j;

        /* XXX How should malloc interact w/ FNONBLOCK? */

        error = RUN_ONCE(&dmio_cleaner_control, dmio_cleaner_init);
        if (error) {
                return error;
        }

        error = proc_vmspace_getref(curproc, &dus->dus_vmspace);
        if (error) {
                return error;
        }

        if (req->req_outbuf.dmbuf_iovcnt != 0) {
                if (req->req_outbuf.dmbuf_iovcnt > IOV_MAX)
                        return (EINVAL);
                len = sizeof(struct iovec) * req->req_outbuf.dmbuf_iovcnt;
                uio_out->uio_iov = malloc(len, M_TEMP, M_WAITOK);
                error = copyin(req->req_outbuf.dmbuf_iov, uio_out->uio_iov,
                    len);
                if (error) {
                        free(uio_out->uio_iov, M_TEMP);
                        return (error);
                }

                for (j = 0, len = 0; j < req->req_outbuf.dmbuf_iovcnt; j++) {
                        len += uio_out->uio_iov[j].iov_len;
                        if (len > SSIZE_MAX) {
                                free(uio_out->uio_iov, M_TEMP);
                                return (EINVAL);
                        }
                }

                uio_out->uio_iovcnt = req->req_outbuf.dmbuf_iovcnt;
                uio_out->uio_resid = len;
                uio_out->uio_rw = UIO_READ;
                uio_out->uio_vmspace = dus->dus_vmspace;

                dreq->dreq_outbuf_type = DMOVER_BUF_UIO;
                dreq->dreq_outbuf.dmbuf_uio = uio_out;
        } else {
                uio_out->uio_iov = NULL;
                uio_out = NULL;
                dreq->dreq_outbuf_type = DMOVER_BUF_NONE;
        }

        memcpy(dreq->dreq_immediate, req->req_immediate,
            sizeof(dreq->dreq_immediate));

        if (dses->dses_ninputs == 0) {
                /* No inputs; all done. */
                return (0);
        }

        dreq->dreq_inbuf_type = DMOVER_BUF_UIO;

        dus->dus_uio_in = malloc(sizeof(struct uio) * dses->dses_ninputs,
            M_TEMP, M_WAITOK);
        memset(dus->dus_uio_in, 0, sizeof(struct uio) * dses->dses_ninputs);

        for (i = 0; i < dses->dses_ninputs; i++) {
                uio_in = &dus->dus_uio_in[i];

                error = copyin(&req->req_inbuf[i], &inbuf, sizeof(inbuf));
                if (error)
                        goto bad;

                if (inbuf.dmbuf_iovcnt > IOV_MAX) {
                        error = EINVAL;
                        goto bad;
                }
                len = sizeof(struct iovec) * inbuf.dmbuf_iovcnt;
                if (len == 0) {
                        error = EINVAL;
                        goto bad;
                }
                uio_in->uio_iov = malloc(len, M_TEMP, M_WAITOK);

                error = copyin(inbuf.dmbuf_iov, uio_in->uio_iov, len);
                if (error) {
                        free(uio_in->uio_iov, M_TEMP);
                        goto bad;
                }

                for (j = 0, len = 0; j < inbuf.dmbuf_iovcnt; j++) {
                        len += uio_in->uio_iov[j].iov_len;
                        if (len > SSIZE_MAX) {
                                free(uio_in->uio_iov, M_TEMP);
                                error = EINVAL;
                                goto bad;
                        }
                }

                if (uio_out != NULL && len != uio_out->uio_resid) {
                        free(uio_in->uio_iov, M_TEMP);
                        error = EINVAL;
                        goto bad;
                }

                uio_in->uio_iovcnt = inbuf.dmbuf_iovcnt;
                uio_in->uio_resid = len;
                uio_in->uio_rw = UIO_WRITE;
                uio_in->uio_vmspace = dus->dus_vmspace;

                dreq->dreq_inbuf[i].dmbuf_uio = uio_in;
        }

        return (0);

 bad:
        if (i > 0) {
                for (--i; i >= 0; i--) {
                        uio_in = &dus->dus_uio_in[i];
                        free(uio_in->uio_iov, M_TEMP);
                }
        }
        free(dus->dus_uio_in, M_TEMP);
        if (uio_out != NULL)
                free(uio_out->uio_iov, M_TEMP);
        uvmspace_free(dus->dus_vmspace);
        return (error);
}

/*
 * dmio_usrreq_fini:
 *
 *      Tear down a request.  Must be called at splsoftclock().
 */
static void
dmio_usrreq_fini(struct dmio_state *ds, struct dmio_usrreq_state *dus)
{
        struct dmover_session *dses = ds->ds_session;
        struct uio *uio_out = &dus->dus_uio_out;
        struct uio *uio_in;
        int i;

        if (uio_out->uio_iov != NULL)
                free(uio_out->uio_iov, M_TEMP);

        if (dses->dses_ninputs) {
                for (i = 0; i < dses->dses_ninputs; i++) {
                        uio_in = &dus->dus_uio_in[i];
                        free(uio_in->uio_iov, M_TEMP);
                }
                free(dus->dus_uio_in, M_TEMP);
        }

        workqueue_enqueue(dmio_cleaner, &dus->dus_work, NULL);
}

static void
dmio_usrreq_fini1(struct work *wk, void *dummy)
{
        struct dmio_usrreq_state *dus = (void *)wk;

        KASSERT(wk == &dus->dus_work);

        uvmspace_free(dus->dus_vmspace);
        pool_put(&dmio_usrreq_state_pool, dus);
}

/*
 * dmio_read:
 *
 *      Read file op.
 */
static int
dmio_read(struct file *fp, off_t *offp, struct uio *uio,
    kauth_cred_t cred, int flags)
{
        struct dmio_state *ds = (struct dmio_state *) fp->f_data;
        struct dmio_usrreq_state *dus;
        struct dmover_request *dreq;
        struct dmio_usrresp resp;
        int error = 0, progress = 0;

        if ((uio->uio_resid % sizeof(resp)) != 0)
                return (EINVAL);

        if (ds->ds_session == NULL)
                return (ENXIO);

        getnanotime(&ds->ds_atime);
        mutex_enter(&ds->ds_lock);

        while (uio->uio_resid != 0) {

                for (;;) {
                        dus = TAILQ_FIRST(&ds->ds_complete);
                        if (dus == NULL) {
                                if (fp->f_flag & FNONBLOCK) {
                                        error = progress ? 0 : EWOULDBLOCK;
                                        goto out;
                                }
                                ds->ds_flags |= DMIO_STATE_READ_WAIT;
                                error = cv_wait_sig(&ds->ds_complete_cv, &ds->ds_lock);
                                if (error)
                                        goto out;
                                continue;
                        }
                        /* Have a completed request. */
                        TAILQ_REMOVE(&ds->ds_complete, dus, dus_q);
                        ds->ds_nreqs--;
                        if (ds->ds_flags & DMIO_STATE_WRITE_WAIT) {
                                ds->ds_flags &= ~DMIO_STATE_WRITE_WAIT;
                                cv_broadcast(&ds->ds_nreqs_cv);
                        }
                        if (ds->ds_flags & DMIO_STATE_SEL) {
                                ds->ds_flags &= ~DMIO_STATE_SEL;
                                selnotify(&ds->ds_selq, POLLIN | POLLRDNORM, 0);
                        }
                        break;
                }

                dreq = dus->dus_req;
                resp.resp_id = dus->dus_id;
                if (dreq->dreq_flags & DMOVER_REQ_ERROR)
                        resp.resp_error = dreq->dreq_error;
                else {
                        resp.resp_error = 0;
                        memcpy(resp.resp_immediate, dreq->dreq_immediate,
                            sizeof(resp.resp_immediate));
                }

                dmio_usrreq_fini(ds, dus);

                mutex_exit(&ds->ds_lock);

                progress = 1;

                dmover_request_free(dreq);

                error = uiomove(&resp, sizeof(resp), uio);
                if (error)
                        return (error);

                mutex_enter(&ds->ds_lock);
        }

 out:
        mutex_exit(&ds->ds_lock);

        return (error);
}

/*
 * dmio_usrreq_done:
 *
 *      Dmover completion callback.
 */
static void
dmio_usrreq_done(struct dmover_request *dreq)
{
        struct dmio_usrreq_state *dus = dreq->dreq_cookie;
        struct dmio_state *ds = dreq->dreq_session->dses_cookie;

        /* We're already at splsoftclock(). */

        mutex_enter(&ds->ds_lock);
        TAILQ_REMOVE(&ds->ds_pending, dus, dus_q);
        if (ds->ds_flags & DMIO_STATE_DEAD) {
                int nreqs = --ds->ds_nreqs;
                mutex_exit(&ds->ds_lock);
                dmio_usrreq_fini(ds, dus);
                dmover_request_free(dreq);
                if (nreqs == 0) {
                        dmio_state_put(ds);
                }
                return;
        }

        TAILQ_INSERT_TAIL(&ds->ds_complete, dus, dus_q);
        if (ds->ds_flags & DMIO_STATE_READ_WAIT) {
                ds->ds_flags &= ~DMIO_STATE_READ_WAIT;
                cv_broadcast(&ds->ds_complete_cv);
        }
        if (ds->ds_flags & DMIO_STATE_SEL) {
                ds->ds_flags &= ~DMIO_STATE_SEL;
                selnotify(&ds->ds_selq, POLLOUT | POLLWRNORM, 0);
        }
        mutex_exit(&ds->ds_lock);
}

/*
 * dmio_write:
 *
 *      Write file op.
 */
static int
dmio_write(struct file *fp, off_t *offp, struct uio *uio,
    kauth_cred_t cred, int flags)
{
        struct dmio_state *ds = (struct dmio_state *) fp->f_data;
        struct dmio_usrreq_state *dus;
        struct dmover_request *dreq;
        struct dmio_usrreq req;
        int error = 0, progress = 0;

        if ((uio->uio_resid % sizeof(req)) != 0)
                return (EINVAL);

        if (ds->ds_session == NULL)
                return (ENXIO);

        getnanotime(&ds->ds_mtime);
        mutex_enter(&ds->ds_lock);

        while (uio->uio_resid != 0) {

                if (ds->ds_nreqs == DMIO_NREQS_MAX) {
                        if (fp->f_flag & FNONBLOCK) {
                                error = progress ? 0 : EWOULDBLOCK;
                                break;
                        }
                        ds->ds_flags |= DMIO_STATE_WRITE_WAIT;
                        error = cv_wait_sig(&ds->ds_complete_cv, &ds->ds_lock);
                        if (error)
                                break;
                        continue;
                }

                ds->ds_nreqs++;

                mutex_exit(&ds->ds_lock);

                progress = 1;

                error = uiomove(&req, sizeof(req), uio);
                if (error) {
                        mutex_enter(&ds->ds_lock);
                        ds->ds_nreqs--;
                        break;
                }

                /* XXX How should this interact with FNONBLOCK? */
                dreq = dmover_request_alloc(ds->ds_session, NULL);
                if (dreq == NULL) {
                        /* XXX */
                        ds->ds_nreqs--;
                        error = ENOMEM;
                        return error;
                }
                dus = pool_get(&dmio_usrreq_state_pool, PR_WAITOK);

                error = dmio_usrreq_init(fp, dus, &req, dreq);
                if (error) {
                        dmover_request_free(dreq);
                        pool_put(&dmio_usrreq_state_pool, dus);
                        return error;
                }

                dreq->dreq_callback = dmio_usrreq_done;
                dreq->dreq_cookie = dus;

                dus->dus_req = dreq;
                dus->dus_id = req.req_id;

                mutex_enter(&ds->ds_lock);

                TAILQ_INSERT_TAIL(&ds->ds_pending, dus, dus_q);

                mutex_exit(&ds->ds_lock);

                dmover_process(dreq);

                mutex_enter(&ds->ds_lock);
        }

        mutex_exit(&ds->ds_lock);

        return (error);
}

static int
dmio_stat(struct file *fp, struct stat *st)
{
        struct dmio_state *ds = fp->f_data;

        (void)memset(st, 0, sizeof(*st));
        KERNEL_LOCK(1, NULL);
        st->st_dev = makedev(cdevsw_lookup_major(&dmoverio_cdevsw), 0);
        st->st_atimespec = ds->ds_atime;
        st->st_mtimespec = ds->ds_mtime;
        st->st_ctimespec = st->st_birthtimespec = ds->ds_btime;
        st->st_uid = kauth_cred_geteuid(fp->f_cred);
        st->st_gid = kauth_cred_getegid(fp->f_cred);
        KERNEL_UNLOCK_ONE(NULL);
        return 0;
}

/*
 * dmio_ioctl:
 *
 *      Ioctl file op.
 */
static int
dmio_ioctl(struct file *fp, u_long cmd, void *data)
{
        struct dmio_state *ds = (struct dmio_state *) fp->f_data;
        int error;

        switch (cmd) {
        case FIONBIO:
        case FIOASYNC:
                return (0);

        case DMIO_SETFUNC:
            {
                struct dmio_setfunc *dsf = data;
                struct dmover_session *dses;

                mutex_enter(&ds->ds_lock);

                if (ds->ds_session != NULL ||
                    (ds->ds_flags & DMIO_STATE_LARVAL) != 0) {
                        mutex_exit(&ds->ds_lock);
                        return (EBUSY);
                }

                ds->ds_flags |= DMIO_STATE_LARVAL;

                mutex_exit(&ds->ds_lock);

                dsf->dsf_name[DMIO_MAX_FUNCNAME - 1] = '\0';
                error = dmover_session_create(dsf->dsf_name, &dses);

                mutex_enter(&ds->ds_lock);

                if (error == 0) {
                        dses->dses_cookie = ds;
                        ds->ds_session = dses;
                }
                ds->ds_flags &= ~DMIO_STATE_LARVAL;

                mutex_exit(&ds->ds_lock);
                break;
            }

        default:
                error = ENOTTY;
        }

        return (error);
}

/*
 * dmio_poll:
 *
 *      Poll file op.
 */
static int
dmio_poll(struct file *fp, int events)
{
        struct dmio_state *ds = (struct dmio_state *) fp->f_data;
        int revents = 0;

        if ((events & (POLLIN | POLLRDNORM | POLLOUT | POLLWRNORM)) == 0)
                return (revents);

        mutex_enter(&ds->ds_lock);

        if (ds->ds_flags & DMIO_STATE_DEAD) {
                /* EOF */
                revents |= events & (POLLIN | POLLRDNORM |
                    POLLOUT | POLLWRNORM);
                goto out;
        }

        /* We can read if there are completed requests. */
        if (events & (POLLIN | POLLRDNORM))
                if (TAILQ_EMPTY(&ds->ds_complete) == 0)
                        revents |= events & (POLLIN | POLLRDNORM);

        /*
         * We can write if there is there are fewer then DMIO_NREQS_MAX
         * are already in the queue.
         */
        if (events & (POLLOUT | POLLWRNORM))
                if (ds->ds_nreqs < DMIO_NREQS_MAX)
                        revents |= events & (POLLOUT | POLLWRNORM);

        if (revents == 0) {
                selrecord(curlwp, &ds->ds_selq);
                ds->ds_flags |= DMIO_STATE_SEL;
        }

 out:
        mutex_exit(&ds->ds_lock);

        return (revents);
}

/*
 * dmio_close:
 *
 *      Close file op.
 */
static int
dmio_close(struct file *fp)
{
        struct dmio_state *ds = (struct dmio_state *) fp->f_data;
        struct dmio_usrreq_state *dus;
        struct dmover_session *dses;

        mutex_enter(&ds->ds_lock);

        ds->ds_flags |= DMIO_STATE_DEAD;

        /* Garbage-collect all the responses on the queue. */
        while ((dus = TAILQ_FIRST(&ds->ds_complete)) != NULL) {
                TAILQ_REMOVE(&ds->ds_complete, dus, dus_q);
                ds->ds_nreqs--;
                mutex_exit(&ds->ds_lock);
                dmover_request_free(dus->dus_req);
                dmio_usrreq_fini(ds, dus);
                mutex_enter(&ds->ds_lock);
        }

        /*
         * If there are any requests pending, we have to wait for
         * them.  Don't free the dmio_state in this case.
         */
        if (ds->ds_nreqs == 0) {
                dses = ds->ds_session;
                mutex_exit(&ds->ds_lock);
                dmio_state_put(ds);
        } else {
                dses = NULL;
                mutex_exit(&ds->ds_lock);
        }

        fp->f_data = NULL;

        if (dses != NULL)
                dmover_session_destroy(dses);

        return (0);
}

static const struct fileops dmio_fileops = {
        .fo_name = "dmio",
        .fo_read = dmio_read,
        .fo_write = dmio_write,
        .fo_ioctl = dmio_ioctl,
        .fo_fcntl = fnullop_fcntl,
        .fo_poll = dmio_poll,
        .fo_stat = dmio_stat,
        .fo_close = dmio_close,
        .fo_kqfilter = fnullop_kqfilter,
        .fo_restart = fnullop_restart,
};

/*
 * dmoverioopen:
 *
 *      Device switch open routine.
 */
int
dmoverioopen(dev_t dev, int flag, int mode, struct lwp *l)
{
        struct dmio_state *ds;
        struct file *fp;
        int error, fd;

        if ((error = fd_allocfile(&fp, &fd)) != 0)
                return (error);

        ds = dmio_state_get();

        return fd_clone(fp, fd, flag, &dmio_fileops, ds);
}