/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * pseudo scsi disk driver
 */

#include <sys/scsi/scsi.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
#include <sys/kmem.h>
#include <sys/taskq.h>
#include <sys/disp.h>
#include <sys/types.h>
#include <sys/buf.h>

#include <sys/emul64.h>
#include <sys/emul64cmd.h>
#include <sys/emul64var.h>

/*
 * Mode sense/select page control
 */
#define MODE_SENSE_PC_CURRENT           0
#define MODE_SENSE_PC_CHANGEABLE        1
#define MODE_SENSE_PC_DEFAULT           2
#define MODE_SENSE_PC_SAVED             3

/*
 * Byte conversion macros
 */
#if     defined(_BIG_ENDIAN)
#define ushort_to_scsi_ushort(n)        (n)
#define uint32_to_scsi_uint32(n)        (n)
#define uint64_to_scsi_uint64(n)        (n)
#elif   defined(_LITTLE_ENDIAN)

#define ushort_to_scsi_ushort(n)                        \
                ((((n) & 0x00ff) << 8) |                \
                (((n)  & 0xff00) >> 8))

#define uint32_to_scsi_uint32(n)                        \
                ((((n) & 0x000000ff) << 24) |           \
                (((n)  & 0x0000ff00) << 8) |            \
                (((n)  & 0x00ff0000) >> 8) |            \
                (((n)  & 0xff000000) >> 24))
#define uint64_to_scsi_uint64(n)                                \
                ((((n) & 0x00000000000000ff) << 56) |           \
                (((n)  & 0x000000000000ff00) << 40) |           \
                (((n)  & 0x0000000000ff0000) << 24) |           \
                (((n)  & 0x00000000ff000000) << 8) |            \
                (((n)  & 0x000000ff00000000) >> 8) |            \
                (((n)  & 0x0000ff0000000000) >> 24) |           \
                (((n)  & 0x00ff000000000000) >> 40) |           \
                (((n)  & 0xff00000000000000) >> 56))
#else
error no _BIG_ENDIAN or _LITTLE_ENDIAN
#endif
#define uint_to_byte0(n)                ((n) & 0xff)
#define uint_to_byte1(n)                (((n)>>8) & 0xff)
#define uint_to_byte2(n)                (((n)>>16) & 0xff)
#define uint_to_byte3(n)                (((n)>>24) & 0xff)

/*
 * struct prop_map
 *
 * This structure maps a property name to the place to store its value.
 */
struct prop_map {
        char            *pm_name;       /* Name of the property. */
        int             *pm_value;      /* Place to store the value. */
};

static int emul64_debug_blklist = 0;

/*
 * Some interesting statistics.  These are protected by the
 * emul64_stats_mutex.  It would be nice to have an ioctl to print them out,
 * but we don't have the development time for that now.  You can at least
 * look at them with adb.
 */

int             emul64_collect_stats = 1; /* Collect stats if non-zero */
kmutex_t        emul64_stats_mutex;     /* Protect these variables */
long            emul64_nowrite_count = 0; /* # active nowrite ranges */
static uint64_t emul64_skipped_io = 0;  /* Skipped I/O operations, because of */
                                        /* EMUL64_WRITE_OFF. */
static uint64_t emul64_skipped_blk = 0; /* Skipped blocks because of */
                                        /* EMUL64_WRITE_OFF. */
static uint64_t emul64_io_ops = 0;      /* Total number of I/O operations */
                                        /* including skipped and actual. */
static uint64_t emul64_io_blocks = 0;   /* Total number of blocks involved */
                                        /* in I/O operations. */
static uint64_t emul64_nonzero = 0;     /* Number of non-zero data blocks */
                                        /* currently held in memory */
static uint64_t emul64_max_list_length = 0; /* Maximum size of a linked */
                                            /* list of non-zero blocks. */
uint64_t emul64_taskq_max = 0;          /* emul64_scsi_start uses the taskq */
                                        /* mechanism to dispatch work. */
                                        /* If the number of entries in the */
                                        /* exceeds the maximum for the queue */
                                        /* the queue a 1 second delay is */
                                        /* encountered in taskq_ent_alloc. */
                                        /* This counter counts the number */
                                        /* times that this happens. */

/*
 * Since emul64 does no physical I/O, operations that would normally be I/O
 * intensive become CPU bound.  An example of this is RAID 5
 * initialization.  When the kernel becomes CPU bound, it looks as if the
 * machine is hung.
 *
 * To avoid this problem, we provide a function, emul64_yield_check, that does a
 * delay from time to time to yield up the CPU.  The following variables
 * are tunables for this algorithm.
 *
 *      emul64_num_delay_called Number of times we called delay.  This is
 *                              not really a tunable.  Rather it is a
 *                              counter that provides useful information
 *                              for adjusting the tunables.
 *      emul64_yield_length     Number of microseconds to yield the CPU.
 *      emul64_yield_period     Number of I/O operations between yields.
 *      emul64_yield_enable     emul64 will yield the CPU, only if this
 *                              variable contains a non-zero value.  This
 *                              allows the yield functionality to be turned
 *                              off for experimentation purposes.
 *
 * The value of 1000 for emul64_yield_period has been determined by
 * experience with running the tests.
 */
static uint64_t         emul64_num_delay_called = 0;
static int              emul64_yield_length = 1000;
static int              emul64_yield_period = 1000;
static int              emul64_yield_enable = 1;
static kmutex_t         emul64_yield_mutex;
static kcondvar_t       emul64_yield_cv;

/*
 * This array establishes a set of tunable variables that can be set by
 * defining properties in the emul64.conf file.
 */
struct prop_map emul64_properties[] = {
        "emul64_collect_stats",         &emul64_collect_stats,
        "emul64_yield_length",          &emul64_yield_length,
        "emul64_yield_period",          &emul64_yield_period,
        "emul64_yield_enable",          &emul64_yield_enable,
        "emul64_max_task",              &emul64_max_task,
        "emul64_task_nthreads",         &emul64_task_nthreads
};

static unsigned char *emul64_zeros = NULL; /* Block of 0s for comparison */

extern void emul64_check_cond(struct scsi_pkt *pkt, uchar_t key,
                                uchar_t asc, uchar_t ascq);
/* ncyl=250000 acyl=2 nhead=24 nsect=357 */
uint_t dkg_rpm = 3600;

static int bsd_mode_sense_dad_mode_geometry(struct scsi_pkt *);
static int bsd_mode_sense_dad_mode_err_recov(struct scsi_pkt *);
static int bsd_mode_sense_modepage_disco_reco(struct scsi_pkt *);
static int bsd_mode_sense_dad_mode_format(struct scsi_pkt *);
static int bsd_mode_sense_dad_mode_cache(struct scsi_pkt *);
static int bsd_readblks(struct emul64 *, ushort_t, ushort_t, diskaddr_t,
                                int, unsigned char *);
static int bsd_writeblks(struct emul64 *, ushort_t, ushort_t, diskaddr_t,
                                int, unsigned char *);
emul64_tgt_t *find_tgt(struct emul64 *, ushort_t, ushort_t);
static blklist_t *bsd_findblk(emul64_tgt_t *, diskaddr_t, avl_index_t *);
static void bsd_allocblk(emul64_tgt_t *, diskaddr_t, caddr_t, avl_index_t);
static void bsd_freeblk(emul64_tgt_t *, blklist_t *);
static void emul64_yield_check();
static emul64_rng_overlap_t bsd_tgt_overlap(emul64_tgt_t *, diskaddr_t, int);

char *emul64_name = "emul64";


/*
 * Initialize globals in this file.
 */
void
emul64_bsd_init()
{
        emul64_zeros = (unsigned char *) kmem_zalloc(DEV_BSIZE, KM_SLEEP);
        mutex_init(&emul64_stats_mutex, NULL, MUTEX_DRIVER, NULL);
        mutex_init(&emul64_yield_mutex, NULL, MUTEX_DRIVER, NULL);
        cv_init(&emul64_yield_cv, NULL, CV_DRIVER, NULL);
}

/*
 * Clean up globals in this file.
 */
void
emul64_bsd_fini()
{
        cv_destroy(&emul64_yield_cv);
        mutex_destroy(&emul64_yield_mutex);
        mutex_destroy(&emul64_stats_mutex);
        if (emul64_zeros != NULL) {
                kmem_free(emul64_zeros, DEV_BSIZE);
                emul64_zeros = NULL;
        }
}

/*
 * Attempt to get the values of the properties that are specified in the
 * emul64_properties array.  If the property exists, copy its value to the
 * specified location.  All the properties have been assigned default
 * values in this driver, so if we cannot get the property that is not a
 * problem.
 */
void
emul64_bsd_get_props(dev_info_t *dip)
{
        uint_t          count;
        uint_t          i;
        struct prop_map *pmp;
        int             *properties;

        for (pmp = emul64_properties, i = 0;
            i < sizeof (emul64_properties) / sizeof (struct prop_map);
            i++, pmp++) {
                if (ddi_prop_lookup_int_array(DDI_DEV_T_ANY, dip,
                    DDI_PROP_DONTPASS, pmp->pm_name, &properties,
                    &count) == DDI_PROP_SUCCESS) {
                        if (count >= 1) {
                                *pmp->pm_value = *properties;
                        }
                        ddi_prop_free((void *) properties);
                }
        }
}

int
emul64_bsd_blkcompare(const void *a1, const void *b1)
{
        blklist_t       *a = (blklist_t *)a1;
        blklist_t       *b = (blklist_t *)b1;

        if (a->bl_blkno < b->bl_blkno)
                return (-1);
        if (a->bl_blkno == b->bl_blkno)
                return (0);
        return (1);
}

/* ARGSUSED 0 */
int
bsd_scsi_start_stop_unit(struct scsi_pkt *pkt)
{
        return (0);
}

/* ARGSUSED 0 */
int
bsd_scsi_test_unit_ready(struct scsi_pkt *pkt)
{
        return (0);
}

/* ARGSUSED 0 */
int
bsd_scsi_request_sense(struct scsi_pkt *pkt)
{
        return (0);
}

int
bsd_scsi_inq_page0(struct scsi_pkt *pkt, uchar_t pqdtype)
{
        struct emul64_cmd       *sp = PKT2CMD(pkt);

        if (sp->cmd_count < 6) {
                cmn_err(CE_CONT, "%s: bsd_scsi_inq_page0: size %d required\n",
                    emul64_name, 6);
                return (EIO);
        }

        sp->cmd_addr[0] = pqdtype;      /* periph qual., dtype */
        sp->cmd_addr[1] = 0;            /* page code */
        sp->cmd_addr[2] = 0;            /* reserved */
        sp->cmd_addr[3] = 6 - 3;        /* length */
        sp->cmd_addr[4] = 0;            /* 1st page */
        sp->cmd_addr[5] = 0x83;         /* 2nd page */

        pkt->pkt_resid = sp->cmd_count - 6;
        return (0);
}

int
bsd_scsi_inq_page83(struct scsi_pkt *pkt, uchar_t pqdtype)
{
        struct emul64           *emul64 = PKT2EMUL64(pkt);
        struct emul64_cmd       *sp = PKT2CMD(pkt);
        int                     instance = ddi_get_instance(emul64->emul64_dip);

        if (sp->cmd_count < 22) {
                cmn_err(CE_CONT, "%s: bsd_scsi_inq_page83: size %d required\n",
                    emul64_name, 22);
                return (EIO);
        }

        sp->cmd_addr[0] = pqdtype;      /* periph qual., dtype */
        sp->cmd_addr[1] = 0x83;         /* page code */
        sp->cmd_addr[2] = 0;            /* reserved */
        sp->cmd_addr[3] = (22 - 8) + 4; /* length */

        sp->cmd_addr[4] = 1;            /* code set - binary */
        sp->cmd_addr[5] = 3;            /* association and device ID type 3 */
        sp->cmd_addr[6] = 0;            /* reserved */
        sp->cmd_addr[7] = 22 - 8;       /* ID length */

        sp->cmd_addr[8] = 0xde;         /* @8: identifier, byte 0 */
        sp->cmd_addr[9] = 0xca;
        sp->cmd_addr[10] = 0xde;
        sp->cmd_addr[11] = 0x80;

        sp->cmd_addr[12] = 0xba;
        sp->cmd_addr[13] = 0xbe;
        sp->cmd_addr[14] = 0xab;
        sp->cmd_addr[15] = 0xba;
                                        /* @22: */

        /*
         * Instances seem to be assigned sequentially, so it unlikely that we
         * will have more than 65535 of them.
         */
        sp->cmd_addr[16] = uint_to_byte1(instance);
        sp->cmd_addr[17] = uint_to_byte0(instance);
        sp->cmd_addr[18] = uint_to_byte1(TGT(sp));
        sp->cmd_addr[19] = uint_to_byte0(TGT(sp));
        sp->cmd_addr[20] = uint_to_byte1(LUN(sp));
        sp->cmd_addr[21] = uint_to_byte0(LUN(sp));

        pkt->pkt_resid = sp->cmd_count - 22;
        return (0);
}

int
bsd_scsi_inquiry(struct scsi_pkt *pkt)
{
        struct emul64_cmd       *sp = PKT2CMD(pkt);
        union scsi_cdb          *cdb = (union scsi_cdb *)pkt->pkt_cdbp;
        emul64_tgt_t            *tgt;
        uchar_t                 pqdtype;
        struct scsi_inquiry     inq;

        EMUL64_MUTEX_ENTER(sp->cmd_emul64);
        tgt = find_tgt(sp->cmd_emul64,
            pkt->pkt_address.a_target, pkt->pkt_address.a_lun);
        EMUL64_MUTEX_EXIT(sp->cmd_emul64);

        if (sp->cmd_count < sizeof (inq)) {
                cmn_err(CE_CONT, "%s: bsd_scsi_inquiry: size %d required\n",
                    emul64_name, (int)sizeof (inq));
                return (EIO);
        }

        if (cdb->cdb_opaque[1] & 0xfc) {
                cmn_err(CE_WARN, "%s: bsd_scsi_inquiry: 0x%x",
                    emul64_name, cdb->cdb_opaque[1]);
                emul64_check_cond(pkt, 0x5, 0x24, 0x0); /* inv. fld in cdb */
                return (0);
        }

        pqdtype = tgt->emul64_tgt_dtype;
        if (cdb->cdb_opaque[1] & 0x1) {
                switch (cdb->cdb_opaque[2]) {
                case 0x00:
                        return (bsd_scsi_inq_page0(pkt, pqdtype));
                case 0x83:
                        return (bsd_scsi_inq_page83(pkt, pqdtype));
                default:
                        cmn_err(CE_WARN, "%s: bsd_scsi_inquiry: "
                            "unsupported 0x%x",
                            emul64_name, cdb->cdb_opaque[2]);
                        return (0);
                }
        }

        /* set up the inquiry data we return */
        (void) bzero((void *)&inq, sizeof (inq));

        inq.inq_dtype = pqdtype;
        inq.inq_ansi = 2;
        inq.inq_rdf = 2;
        inq.inq_len = sizeof (inq) - 4;
        inq.inq_wbus16 = 1;
        inq.inq_cmdque = 1;

        (void) bcopy(tgt->emul64_tgt_inq, inq.inq_vid,
            sizeof (tgt->emul64_tgt_inq));
        (void) bcopy("1", inq.inq_revision, 2);
        (void) bcopy((void *)&inq, sp->cmd_addr, sizeof (inq));

        pkt->pkt_resid = sp->cmd_count - sizeof (inq);
        return (0);
}

/* ARGSUSED 0 */
int
bsd_scsi_format(struct scsi_pkt *pkt)
{
        return (0);
}

int
bsd_scsi_io(struct scsi_pkt *pkt)
{
        struct emul64_cmd       *sp = PKT2CMD(pkt);
        union scsi_cdb          *cdb = (union scsi_cdb *)pkt->pkt_cdbp;
        diskaddr_t              lblkno;
        int                     nblks;

        switch (cdb->scc_cmd) {
        case SCMD_READ:
                        lblkno = (uint32_t)GETG0ADDR(cdb);
                        nblks = GETG0COUNT(cdb);
                        pkt->pkt_resid = bsd_readblks(sp->cmd_emul64,
                            pkt->pkt_address.a_target, pkt->pkt_address.a_lun,
                            lblkno, nblks, sp->cmd_addr);
                        if (emul64debug) {
                                cmn_err(CE_CONT, "%s: bsd_scsi_io: "
                                    "read g0 blk=%lld (0x%llx) nblks=%d\n",
                                    emul64_name, lblkno, lblkno, nblks);
                        }
                break;
        case SCMD_WRITE:
                        lblkno = (uint32_t)GETG0ADDR(cdb);
                        nblks = GETG0COUNT(cdb);
                        pkt->pkt_resid = bsd_writeblks(sp->cmd_emul64,
                            pkt->pkt_address.a_target, pkt->pkt_address.a_lun,
                            lblkno, nblks, sp->cmd_addr);
                        if (emul64debug) {
                                cmn_err(CE_CONT, "%s: bsd_scsi_io: "
                                    "write g0 blk=%lld (0x%llx) nblks=%d\n",
                                    emul64_name, lblkno, lblkno, nblks);
                        }
                break;
        case SCMD_READ_G1:
                        lblkno = (uint32_t)GETG1ADDR(cdb);
                        nblks = GETG1COUNT(cdb);
                        pkt->pkt_resid = bsd_readblks(sp->cmd_emul64,
                            pkt->pkt_address.a_target, pkt->pkt_address.a_lun,
                            lblkno, nblks, sp->cmd_addr);
                        if (emul64debug) {
                                cmn_err(CE_CONT, "%s: bsd_scsi_io: "
                                    "read g1 blk=%lld (0x%llx) nblks=%d\n",
                                    emul64_name, lblkno, lblkno, nblks);
                        }
                break;
        case SCMD_WRITE_G1:
                        lblkno = (uint32_t)GETG1ADDR(cdb);
                        nblks = GETG1COUNT(cdb);
                        pkt->pkt_resid = bsd_writeblks(sp->cmd_emul64,
                            pkt->pkt_address.a_target, pkt->pkt_address.a_lun,
                            lblkno, nblks, sp->cmd_addr);
                        if (emul64debug) {
                                cmn_err(CE_CONT, "%s: bsd_scsi_io: "
                                    "write g1 blk=%lld (0x%llx) nblks=%d\n",
                                    emul64_name, lblkno, lblkno, nblks);
                        }
                break;
        case SCMD_READ_G4:
                        lblkno = GETG4ADDR(cdb);
                        lblkno <<= 32;
                        lblkno |= (uint32_t)GETG4ADDRTL(cdb);
                        nblks = GETG4COUNT(cdb);
                        pkt->pkt_resid = bsd_readblks(sp->cmd_emul64,
                            pkt->pkt_address.a_target, pkt->pkt_address.a_lun,
                            lblkno, nblks, sp->cmd_addr);
                        if (emul64debug) {
                                cmn_err(CE_CONT, "%s: bsd_scsi_io: "
                                    "read g4 blk=%lld (0x%llx) nblks=%d\n",
                                    emul64_name, lblkno, lblkno, nblks);
                        }
                break;
        case SCMD_WRITE_G4:
                        lblkno = GETG4ADDR(cdb);
                        lblkno <<= 32;
                        lblkno |= (uint32_t)GETG4ADDRTL(cdb);
                        nblks = GETG4COUNT(cdb);
                        pkt->pkt_resid = bsd_writeblks(sp->cmd_emul64,
                            pkt->pkt_address.a_target, pkt->pkt_address.a_lun,
                            lblkno, nblks, sp->cmd_addr);
                        if (emul64debug) {
                                cmn_err(CE_CONT, "%s: bsd_scsi_io: "
                                    "write g4 blk=%lld (0x%llx) nblks=%d\n",
                                    emul64_name, lblkno, lblkno, nblks);
                        }
                break;
        default:
                cmn_err(CE_WARN, "%s: bsd_scsi_io: unhandled I/O: 0x%x",
                    emul64_name, cdb->scc_cmd);
                break;
        }

        if (pkt->pkt_resid != 0)
                cmn_err(CE_WARN, "%s: bsd_scsi_io: "
                    "pkt_resid: 0x%lx, lblkno %lld, nblks %d",
                    emul64_name, pkt->pkt_resid, lblkno, nblks);

        return (0);
}

int
bsd_scsi_log_sense(struct scsi_pkt *pkt)
{
        union scsi_cdb          *cdb = (union scsi_cdb *)pkt->pkt_cdbp;
        struct emul64_cmd       *sp = PKT2CMD(pkt);
        int                     page_code;

        if (sp->cmd_count < 9) {
                cmn_err(CE_CONT, "%s: bsd_scsi_log_sense size %d required\n",
                    emul64_name, 9);
                return (EIO);
        }

        page_code = cdb->cdb_opaque[2] & 0x3f;
        if (page_code) {
                cmn_err(CE_CONT, "%s: bsd_scsi_log_sense: "
                    "page 0x%x not supported\n", emul64_name, page_code);
                emul64_check_cond(pkt, 0x5, 0x24, 0x0); /* inv. fld in cdb */
                return (0);
        }

        sp->cmd_addr[0] = 0;            /* page code */
        sp->cmd_addr[1] = 0;            /* reserved */
        sp->cmd_addr[2] = 0;            /* MSB of page length */
        sp->cmd_addr[3] = 8 - 3;        /* LSB of page length */

        sp->cmd_addr[4] = 0;            /* MSB of parameter code */
        sp->cmd_addr[5] = 0;            /* LSB of parameter code */
        sp->cmd_addr[6] = 0;            /* parameter control byte */
        sp->cmd_addr[7] = 4 - 3;        /* parameter length */
        sp->cmd_addr[8] = 0x0;          /* parameter value */

        pkt->pkt_resid = sp->cmd_count - 9;
        return (0);
}

int
bsd_scsi_mode_sense(struct scsi_pkt *pkt)
{
        union scsi_cdb  *cdb = (union scsi_cdb *)pkt->pkt_cdbp;
        int             page_control;
        int             page_code;
        int             rval = 0;

        switch (cdb->scc_cmd) {
        case SCMD_MODE_SENSE:
                        page_code = cdb->cdb_opaque[2] & 0x3f;
                        page_control = (cdb->cdb_opaque[2] >> 6) & 0x03;
                        if (emul64debug) {
                                cmn_err(CE_CONT, "%s: bsd_scsi_mode_sense: "
                                    "page=0x%x control=0x%x nbytes=%d\n",
                                    emul64_name, page_code, page_control,
                                    GETG0COUNT(cdb));
                        }
                break;
        case SCMD_MODE_SENSE_G1:
                        page_code = cdb->cdb_opaque[2] & 0x3f;
                        page_control = (cdb->cdb_opaque[2] >> 6) & 0x03;
                        if (emul64debug) {
                                cmn_err(CE_CONT, "%s: bsd_scsi_mode_sense: "
                                    "page=0x%x control=0x%x nbytes=%d\n",
                                    emul64_name, page_code, page_control,
                                    GETG1COUNT(cdb));
                        }
                break;
        default:
                cmn_err(CE_CONT, "%s: bsd_scsi_mode_sense: "
                    "cmd 0x%x not supported\n", emul64_name, cdb->scc_cmd);
                return (EIO);
        }

        switch (page_code) {
        case DAD_MODE_GEOMETRY:
                rval = bsd_mode_sense_dad_mode_geometry(pkt);
                break;
        case DAD_MODE_ERR_RECOV:
                rval = bsd_mode_sense_dad_mode_err_recov(pkt);
                break;
        case MODEPAGE_DISCO_RECO:
                rval = bsd_mode_sense_modepage_disco_reco(pkt);
                break;
        case DAD_MODE_FORMAT:
                rval = bsd_mode_sense_dad_mode_format(pkt);
                break;
        case DAD_MODE_CACHE:
                rval = bsd_mode_sense_dad_mode_cache(pkt);
                break;
        default:
                cmn_err(CE_CONT, "%s: bsd_scsi_mode_sense: "
                    "page 0x%x not supported\n", emul64_name, page_code);
                rval = EIO;
                break;
        }

        return (rval);
}


static int
bsd_mode_sense_dad_mode_geometry(struct scsi_pkt *pkt)
{
        struct emul64_cmd       *sp = PKT2CMD(pkt);
        union scsi_cdb          *cdb = (union scsi_cdb *)pkt->pkt_cdbp;
        uchar_t                 *addr = (uchar_t *)sp->cmd_addr;
        emul64_tgt_t            *tgt;
        int                     page_control;
        struct mode_header      header;
        struct mode_geometry    page4;
        int                     ncyl;
        int                     rval = 0;

        page_control = (cdb->cdb_opaque[2] >> 6) & 0x03;

        if (emul64debug) {
                cmn_err(CE_CONT, "%s: bsd_mode_sense_dad_mode_geometry: "
                    "pc=%d n=%d\n", emul64_name, page_control, sp->cmd_count);
        }

        if (sp->cmd_count < (sizeof (header) + sizeof (page4))) {
                cmn_err(CE_CONT, "%s: bsd_mode_sense_dad_mode_geometry: "
                    "size %d required\n",
                    emul64_name, (int)(sizeof (header) + sizeof (page4)));
                return (EIO);
        }

        (void) bzero(&header, sizeof (header));
        (void) bzero(&page4, sizeof (page4));

        header.length = sizeof (header) + sizeof (page4) - 1;
        header.bdesc_length = 0;

        page4.mode_page.code = DAD_MODE_GEOMETRY;
        page4.mode_page.ps = 1;
        page4.mode_page.length = sizeof (page4) - sizeof (struct mode_page);

        switch (page_control) {
        case MODE_SENSE_PC_CURRENT:
        case MODE_SENSE_PC_DEFAULT:
        case MODE_SENSE_PC_SAVED:
                EMUL64_MUTEX_ENTER(sp->cmd_emul64);
                tgt = find_tgt(sp->cmd_emul64,
                    pkt->pkt_address.a_target, pkt->pkt_address.a_lun);
                EMUL64_MUTEX_EXIT(sp->cmd_emul64);
                ncyl = tgt->emul64_tgt_ncyls;
                page4.cyl_ub = uint_to_byte2(ncyl);
                page4.cyl_mb = uint_to_byte1(ncyl);
                page4.cyl_lb = uint_to_byte0(ncyl);
                page4.heads = uint_to_byte0(tgt->emul64_tgt_nheads);
                page4.rpm = ushort_to_scsi_ushort(dkg_rpm);
                break;
        case MODE_SENSE_PC_CHANGEABLE:
                page4.cyl_ub = 0xff;
                page4.cyl_mb = 0xff;
                page4.cyl_lb = 0xff;
                page4.heads = 0xff;
                page4.rpm = 0xffff;
                break;
        }

        (void) bcopy(&header, addr, sizeof (header));
        (void) bcopy(&page4, addr + sizeof (header), sizeof (page4));

        pkt->pkt_resid = sp->cmd_count - sizeof (page4) - sizeof (header);
        rval = 0;

        return (rval);
}

static int
bsd_mode_sense_dad_mode_err_recov(struct scsi_pkt *pkt)
{
        struct emul64_cmd       *sp = PKT2CMD(pkt);
        union scsi_cdb          *cdb = (union scsi_cdb *)pkt->pkt_cdbp;
        uchar_t                 *addr = (uchar_t *)sp->cmd_addr;
        int                     page_control;
        struct mode_header      header;
        struct mode_err_recov   page1;
        int                     rval = 0;

        page_control = (cdb->cdb_opaque[2] >> 6) & 0x03;

        if (emul64debug) {
                cmn_err(CE_CONT, "%s: bsd_mode_sense_dad_mode_err_recov: "
                    "pc=%d n=%d\n", emul64_name, page_control, sp->cmd_count);
        }

        if (sp->cmd_count < (sizeof (header) + sizeof (page1))) {
                cmn_err(CE_CONT, "%s: bsd_mode_sense_dad_mode_err_recov: "
                    "size %d required\n",
                    emul64_name, (int)(sizeof (header) + sizeof (page1)));
                return (EIO);
        }

        (void) bzero(&header, sizeof (header));
        (void) bzero(&page1, sizeof (page1));

        header.length = sizeof (header) + sizeof (page1) - 1;
        header.bdesc_length = 0;

        page1.mode_page.code = DAD_MODE_ERR_RECOV;
        page1.mode_page.ps = 1;
        page1.mode_page.length = sizeof (page1) - sizeof (struct mode_page);

        switch (page_control) {
        case MODE_SENSE_PC_CURRENT:
        case MODE_SENSE_PC_DEFAULT:
        case MODE_SENSE_PC_SAVED:
                break;
        case MODE_SENSE_PC_CHANGEABLE:
                break;
        }

        (void) bcopy(&header, addr, sizeof (header));
        (void) bcopy(&page1, addr + sizeof (header), sizeof (page1));

        pkt->pkt_resid = sp->cmd_count - sizeof (page1) - sizeof (header);
        rval = 0;

        return (rval);
}

static int
bsd_mode_sense_modepage_disco_reco(struct scsi_pkt *pkt)
{
        struct emul64_cmd       *sp = PKT2CMD(pkt);
        union scsi_cdb          *cdb = (union scsi_cdb *)pkt->pkt_cdbp;
        int                     rval = 0;
        uchar_t                 *addr = (uchar_t *)sp->cmd_addr;
        int                     page_control;
        struct mode_header      header;
        struct mode_disco_reco  page2;

        page_control = (cdb->cdb_opaque[2] >> 6) & 0x03;

        if (emul64debug) {
                cmn_err(CE_CONT, "%s: bsd_mode_sense_modepage_disco_reco: "
                    "pc=%d n=%d\n", emul64_name, page_control, sp->cmd_count);
        }

        if (sp->cmd_count < (sizeof (header) + sizeof (page2))) {
                cmn_err(CE_CONT, "%s: bsd_mode_sense_modepage_disco_reco: "
                    "size %d required\n",
                    emul64_name, (int)(sizeof (header) + sizeof (page2)));
                return (EIO);
        }

        (void) bzero(&header, sizeof (header));
        (void) bzero(&page2, sizeof (page2));

        header.length = sizeof (header) + sizeof (page2) - 1;
        header.bdesc_length = 0;

        page2.mode_page.code = MODEPAGE_DISCO_RECO;
        page2.mode_page.ps = 1;
        page2.mode_page.length = sizeof (page2) - sizeof (struct mode_page);

        switch (page_control) {
        case MODE_SENSE_PC_CURRENT:
        case MODE_SENSE_PC_DEFAULT:
        case MODE_SENSE_PC_SAVED:
                break;
        case MODE_SENSE_PC_CHANGEABLE:
                break;
        }

        (void) bcopy(&header, addr, sizeof (header));
        (void) bcopy(&page2, addr + sizeof (header), sizeof (page2));

        pkt->pkt_resid = sp->cmd_count - sizeof (page2) - sizeof (header);
        rval = 0;

        return (rval);
}

static int
bsd_mode_sense_dad_mode_format(struct scsi_pkt *pkt)
{
        struct emul64_cmd       *sp = PKT2CMD(pkt);
        union scsi_cdb          *cdb = (union scsi_cdb *)pkt->pkt_cdbp;
        uchar_t                 *addr = (uchar_t *)sp->cmd_addr;
        emul64_tgt_t            *tgt;
        int                     page_control;
        struct mode_header      header;
        struct mode_format      page3;
        int                     rval = 0;

        page_control = (cdb->cdb_opaque[2] >> 6) & 0x03;

        if (emul64debug) {
                cmn_err(CE_CONT, "%s: bsd_mode_sense_dad_mode_format: "
                    "pc=%d n=%d\n", emul64_name, page_control, sp->cmd_count);
        }

        if (sp->cmd_count < (sizeof (header) + sizeof (page3))) {
                cmn_err(CE_CONT, "%s: bsd_mode_sense_dad_mode_format: "
                    "size %d required\n",
                    emul64_name, (int)(sizeof (header) + sizeof (page3)));
                return (EIO);
        }

        (void) bzero(&header, sizeof (header));
        (void) bzero(&page3, sizeof (page3));

        header.length = sizeof (header) + sizeof (page3) - 1;
        header.bdesc_length = 0;

        page3.mode_page.code = DAD_MODE_FORMAT;
        page3.mode_page.ps = 1;
        page3.mode_page.length = sizeof (page3) - sizeof (struct mode_page);

        switch (page_control) {
        case MODE_SENSE_PC_CURRENT:
        case MODE_SENSE_PC_DEFAULT:
        case MODE_SENSE_PC_SAVED:
                page3.data_bytes_sect = ushort_to_scsi_ushort(DEV_BSIZE);
                page3.interleave = ushort_to_scsi_ushort(1);
                EMUL64_MUTEX_ENTER(sp->cmd_emul64);
                tgt = find_tgt(sp->cmd_emul64,
                    pkt->pkt_address.a_target, pkt->pkt_address.a_lun);
                EMUL64_MUTEX_EXIT(sp->cmd_emul64);
                page3.sect_track = ushort_to_scsi_ushort(tgt->emul64_tgt_nsect);
                break;
        case MODE_SENSE_PC_CHANGEABLE:
                break;
        }

        (void) bcopy(&header, addr, sizeof (header));
        (void) bcopy(&page3, addr + sizeof (header), sizeof (page3));

        pkt->pkt_resid = sp->cmd_count - sizeof (page3) - sizeof (header);
        rval = 0;

        return (rval);
}

static int
bsd_mode_sense_dad_mode_cache(struct scsi_pkt *pkt)
{
        struct emul64_cmd       *sp = PKT2CMD(pkt);
        union scsi_cdb          *cdb = (union scsi_cdb *)pkt->pkt_cdbp;
        uchar_t                 *addr = (uchar_t *)sp->cmd_addr;
        int                     page_control;
        struct mode_header      header;
        struct mode_cache       page8;
        int                     rval = 0;

        page_control = (cdb->cdb_opaque[2] >> 6) & 0x03;

        if (emul64debug) {
                cmn_err(CE_CONT, "%s: bsd_mode_sense_dad_mode_cache: "
                    "pc=%d n=%d\n", emul64_name, page_control, sp->cmd_count);
        }

        if (sp->cmd_count < (sizeof (header) + sizeof (page8))) {
                cmn_err(CE_CONT, "%s: bsd_mode_sense_dad_mode_cache: "
                    "size %d required\n",
                    emul64_name, (int)(sizeof (header) + sizeof (page8)));
                return (EIO);
        }

        (void) bzero(&header, sizeof (header));
        (void) bzero(&page8, sizeof (page8));

        header.length = sizeof (header) + sizeof (page8) - 1;
        header.bdesc_length = 0;

        page8.mode_page.code = DAD_MODE_CACHE;
        page8.mode_page.ps = 1;
        page8.mode_page.length = sizeof (page8) - sizeof (struct mode_page);

        switch (page_control) {
        case MODE_SENSE_PC_CURRENT:
        case MODE_SENSE_PC_DEFAULT:
        case MODE_SENSE_PC_SAVED:
                break;
        case MODE_SENSE_PC_CHANGEABLE:
                break;
        }

        (void) bcopy(&header, addr, sizeof (header));
        (void) bcopy(&page8, addr + sizeof (header), sizeof (page8));

        pkt->pkt_resid = sp->cmd_count - sizeof (page8) - sizeof (header);
        rval = 0;

        return (rval);
}

/* ARGSUSED 0 */
int
bsd_scsi_mode_select(struct scsi_pkt *pkt)
{
        return (0);
}

int
bsd_scsi_read_capacity_8(struct scsi_pkt *pkt)
{
        struct emul64_cmd       *sp = PKT2CMD(pkt);
        emul64_tgt_t            *tgt;
        struct scsi_capacity    cap;
        int                     rval = 0;

        EMUL64_MUTEX_ENTER(sp->cmd_emul64);
        tgt = find_tgt(sp->cmd_emul64,
            pkt->pkt_address.a_target, pkt->pkt_address.a_lun);
        EMUL64_MUTEX_EXIT(sp->cmd_emul64);
        if (tgt->emul64_tgt_sectors > 0xffffffff)
                cap.capacity = 0xffffffff;
        else
                cap.capacity =
                    uint32_to_scsi_uint32(tgt->emul64_tgt_sectors);
        cap.lbasize = uint32_to_scsi_uint32((uint_t)DEV_BSIZE);

        pkt->pkt_resid = sp->cmd_count - sizeof (struct scsi_capacity);

        (void) bcopy(&cap, (caddr_t)sp->cmd_addr,
            sizeof (struct scsi_capacity));
        return (rval);
}

int
bsd_scsi_read_capacity_16(struct scsi_pkt *pkt)
{
        struct emul64_cmd       *sp = PKT2CMD(pkt);
        emul64_tgt_t            *tgt;
        struct scsi_capacity_16 cap;
        int                     rval = 0;

        EMUL64_MUTEX_ENTER(sp->cmd_emul64);
        tgt = find_tgt(sp->cmd_emul64,
            pkt->pkt_address.a_target, pkt->pkt_address.a_lun);
        EMUL64_MUTEX_EXIT(sp->cmd_emul64);

        cap.sc_capacity = uint64_to_scsi_uint64(tgt->emul64_tgt_sectors);
        cap.sc_lbasize = uint32_to_scsi_uint32((uint_t)DEV_BSIZE);
        cap.sc_rto_en = 0;
        cap.sc_prot_en = 0;
        cap.sc_rsvd0 = 0;
        bzero(&cap.sc_rsvd1[0], sizeof (cap.sc_rsvd1));

        pkt->pkt_resid = sp->cmd_count - sizeof (struct scsi_capacity_16);

        (void) bcopy(&cap, (caddr_t)sp->cmd_addr,
            sizeof (struct scsi_capacity_16));
        return (rval);
}
int
bsd_scsi_read_capacity(struct scsi_pkt *pkt)
{
        return (bsd_scsi_read_capacity_8(pkt));
}


/* ARGSUSED 0 */
int
bsd_scsi_reserve(struct scsi_pkt *pkt)
{
        return (0);
}

/* ARGSUSED 0 */
int
bsd_scsi_release(struct scsi_pkt *pkt)
{
        return (0);
}


int
bsd_scsi_read_defect_list(struct scsi_pkt *pkt)
{
        pkt->pkt_resid = 0;
        return (0);
}


/* ARGSUSED 0 */
int
bsd_scsi_reassign_block(struct scsi_pkt *pkt)
{
        return (0);
}


static int
bsd_readblks(struct emul64 *emul64, ushort_t target, ushort_t lun,
    diskaddr_t blkno, int nblks, unsigned char *bufaddr)
{
        emul64_tgt_t    *tgt;
        blklist_t       *blk;
        emul64_rng_overlap_t overlap;
        int             i = 0;

        if (emul64debug) {
                cmn_err(CE_CONT, "%s: bsd_readblks: "
                    "<%d,%d> blk %llu (0x%llx) nblks %d\n",
                    emul64_name, target, lun, blkno, blkno, nblks);
        }

        emul64_yield_check();

        EMUL64_MUTEX_ENTER(emul64);
        tgt = find_tgt(emul64, target, lun);
        EMUL64_MUTEX_EXIT(emul64);
        if (tgt == NULL) {
                cmn_err(CE_WARN, "%s: bsd_readblks: no target for %d,%d\n",
                    emul64_name, target, lun);
                goto unlocked_out;
        }

        if (emul64_collect_stats) {
                mutex_enter(&emul64_stats_mutex);
                emul64_io_ops++;
                emul64_io_blocks += nblks;
                mutex_exit(&emul64_stats_mutex);
        }
        mutex_enter(&tgt->emul64_tgt_blk_lock);

        /*
         * Keep the ioctls from changing the nowrite list for the duration
         * of this I/O by grabbing emul64_tgt_nw_lock.  This will keep the
         * results from our call to bsd_tgt_overlap from changing while we
         * do the I/O.
         */
        rw_enter(&tgt->emul64_tgt_nw_lock, RW_READER);

        overlap = bsd_tgt_overlap(tgt, blkno, nblks);
        switch (overlap) {
        case O_SAME:
        case O_SUBSET:
        case O_OVERLAP:
                cmn_err(CE_WARN, "%s: bsd_readblks: "
                    "read to blocked area %lld,%d\n",
                    emul64_name, blkno, nblks);
                rw_exit(&tgt->emul64_tgt_nw_lock);
                goto errout;
        case O_NONE:
                break;
        }
        for (i = 0; i < nblks; i++) {
                if (emul64_debug_blklist)
                        cmn_err(CE_CONT, "%s: bsd_readblks: "
                            "%d of %d: blkno %lld\n",
                            emul64_name, i+1, nblks, blkno);
                if (blkno > tgt->emul64_tgt_sectors)
                        break;
                blk = bsd_findblk(tgt, blkno, NULL);
                if (blk) {
                        (void) bcopy(blk->bl_data, bufaddr, DEV_BSIZE);
                } else {
                        (void) bzero(bufaddr, DEV_BSIZE);
                }
                blkno++;
                bufaddr += DEV_BSIZE;
        }
        rw_exit(&tgt->emul64_tgt_nw_lock);

errout:
        mutex_exit(&tgt->emul64_tgt_blk_lock);

unlocked_out:
        return ((nblks - i) * DEV_BSIZE);
}


static int
bsd_writeblks(struct emul64 *emul64, ushort_t target, ushort_t lun,
    diskaddr_t blkno, int nblks, unsigned char *bufaddr)
{
        emul64_tgt_t    *tgt;
        blklist_t       *blk;
        emul64_rng_overlap_t overlap;
        avl_index_t     where;
        int             i = 0;

        if (emul64debug) {
                cmn_err(CE_CONT, "%s: bsd_writeblks: "
                    "<%d,%d> blk %llu (0x%llx) nblks %d\n",
                    emul64_name, target, lun, blkno, blkno, nblks);
        }

        emul64_yield_check();

        EMUL64_MUTEX_ENTER(emul64);
        tgt = find_tgt(emul64, target, lun);
        EMUL64_MUTEX_EXIT(emul64);
        if (tgt == NULL) {
                cmn_err(CE_WARN, "%s: bsd_writeblks: no target for %d,%d\n",
                    emul64_name, target, lun);
                goto unlocked_out;
        }

        if (emul64_collect_stats) {
                mutex_enter(&emul64_stats_mutex);
                emul64_io_ops++;
                emul64_io_blocks += nblks;
                mutex_exit(&emul64_stats_mutex);
        }
        mutex_enter(&tgt->emul64_tgt_blk_lock);

        /*
         * Keep the ioctls from changing the nowrite list for the duration
         * of this I/O by grabbing emul64_tgt_nw_lock.  This will keep the
         * results from our call to bsd_tgt_overlap from changing while we
         * do the I/O.
         */
        rw_enter(&tgt->emul64_tgt_nw_lock, RW_READER);
        overlap = bsd_tgt_overlap(tgt, blkno, nblks);
        switch (overlap) {
        case O_SAME:
        case O_SUBSET:
                if (emul64_collect_stats) {
                        mutex_enter(&emul64_stats_mutex);
                        emul64_skipped_io++;
                        emul64_skipped_blk += nblks;
                        mutex_exit(&emul64_stats_mutex);
                }
                rw_exit(&tgt->emul64_tgt_nw_lock);
                mutex_exit(&tgt->emul64_tgt_blk_lock);
                return (0);
        case O_OVERLAP:
        case O_NONE:
                break;
        }
        for (i = 0; i < nblks; i++) {
                if ((overlap == O_NONE) ||
                    (bsd_tgt_overlap(tgt, blkno, 1) == O_NONE)) {
                        /*
                         * If there was no overlap for the entire I/O range
                         * or if there is no overlap for this particular
                         * block, then we need to do the write.
                         */
                        if (emul64_debug_blklist)
                                cmn_err(CE_CONT, "%s: bsd_writeblks: "
                                    "%d of %d: blkno %lld\n",
                                    emul64_name, i+1, nblks, blkno);
                        if (blkno > tgt->emul64_tgt_sectors) {
                                cmn_err(CE_WARN, "%s: bsd_writeblks: "
                                    "blkno %lld, tgt_sectors %lld\n",
                                    emul64_name, blkno,
                                    tgt->emul64_tgt_sectors);
                                break;
                        }

                        blk = bsd_findblk(tgt, blkno, &where);
                        if (bcmp(bufaddr, emul64_zeros, DEV_BSIZE) == 0) {
                                if (blk) {
                                        bsd_freeblk(tgt, blk);
                                }
                        } else {
                                if (blk) {
                                        (void) bcopy(bufaddr, blk->bl_data,
                                            DEV_BSIZE);
                                } else {
                                        bsd_allocblk(tgt, blkno,
                                            (caddr_t)bufaddr, where);
                                }
                        }
                }
                blkno++;
                bufaddr += DEV_BSIZE;
        }

        /*
         * Now that we're done with our I/O, allow the ioctls to change the
         * nowrite list.
         */
        rw_exit(&tgt->emul64_tgt_nw_lock);
        mutex_exit(&tgt->emul64_tgt_blk_lock);

unlocked_out:
        return ((nblks - i) * DEV_BSIZE);
}

emul64_tgt_t *
find_tgt(struct emul64 *emul64, ushort_t target, ushort_t lun)
{
        emul64_tgt_t    *tgt;

        tgt = emul64->emul64_tgt;
        while (tgt) {
                if (tgt->emul64_tgt_saddr.a_target == target &&
                    tgt->emul64_tgt_saddr.a_lun == lun) {
                        break;
                }
                tgt = tgt->emul64_tgt_next;
        }
        return (tgt);

}

/*
 * Free all blocks that are part of the specified range.
 */
int
bsd_freeblkrange(emul64_tgt_t *tgt, emul64_range_t *range)
{
        blklist_t       *blk;
        blklist_t       *nextblk;

        ASSERT(mutex_owned(&tgt->emul64_tgt_blk_lock));
        for (blk = (blklist_t *)avl_first(&tgt->emul64_tgt_data);
            blk != NULL;
            blk = nextblk) {
                /*
                 * We need to get the next block pointer now, because blk
                 * will be freed inside the if statement.
                 */
                nextblk = AVL_NEXT(&tgt->emul64_tgt_data, blk);

                if (emul64_overlap(range, blk->bl_blkno, (size_t)1) != O_NONE) {
                        bsd_freeblk(tgt, blk);
                }
        }
        return (0);
}

static blklist_t *
bsd_findblk(emul64_tgt_t *tgt, diskaddr_t blkno, avl_index_t *where)
{
        blklist_t       *blk;
        blklist_t       search;

        ASSERT(mutex_owned(&tgt->emul64_tgt_blk_lock));

        search.bl_blkno = blkno;
        blk = (blklist_t *)avl_find(&tgt->emul64_tgt_data, &search, where);
        return (blk);
}


static void
bsd_allocblk(emul64_tgt_t *tgt,
                diskaddr_t blkno,
                caddr_t data,
                avl_index_t where)
{
        blklist_t       *blk;

        if (emul64_debug_blklist)
                cmn_err(CE_CONT, "%s: bsd_allocblk: %llu\n",
                    emul64_name, blkno);

        ASSERT(mutex_owned(&tgt->emul64_tgt_blk_lock));

        blk = (blklist_t *)kmem_zalloc(sizeof (blklist_t), KM_SLEEP);
        blk->bl_data = (uchar_t *)kmem_zalloc(DEV_BSIZE, KM_SLEEP);
        blk->bl_blkno = blkno;
        (void) bcopy(data, blk->bl_data, DEV_BSIZE);
        avl_insert(&tgt->emul64_tgt_data, (void *) blk, where);

        if (emul64_collect_stats) {
                mutex_enter(&emul64_stats_mutex);
                emul64_nonzero++;
                tgt->emul64_list_length++;
                if (tgt->emul64_list_length > emul64_max_list_length) {
                        emul64_max_list_length = tgt->emul64_list_length;
                }
                mutex_exit(&emul64_stats_mutex);
        }
}

static void
bsd_freeblk(emul64_tgt_t *tgt, blklist_t *blk)
{
        if (emul64_debug_blklist)
                cmn_err(CE_CONT, "%s: bsd_freeblk: <%d,%d> blk=%lld\n",
                    emul64_name, tgt->emul64_tgt_saddr.a_target,
                    tgt->emul64_tgt_saddr.a_lun, blk->bl_blkno);

        ASSERT(mutex_owned(&tgt->emul64_tgt_blk_lock));

        avl_remove(&tgt->emul64_tgt_data, (void *) blk);
        if (emul64_collect_stats) {
                mutex_enter(&emul64_stats_mutex);
                emul64_nonzero--;
                tgt->emul64_list_length--;
                mutex_exit(&emul64_stats_mutex);
        }
        kmem_free(blk->bl_data, DEV_BSIZE);
        kmem_free(blk, sizeof (blklist_t));
}

/*
 * Look for overlap between a nowrite range and a block range.
 *
 * NOTE:  Callers of this function must hold the tgt->emul64_tgt_nw_lock
 *        lock.  For the purposes of this function, a reader lock is
 *        sufficient.
 */
static emul64_rng_overlap_t
bsd_tgt_overlap(emul64_tgt_t *tgt, diskaddr_t blkno, int count)
{
        emul64_nowrite_t        *nw;
        emul64_rng_overlap_t    rv = O_NONE;

        for (nw = tgt->emul64_tgt_nowrite;
            (nw != NULL) && (rv == O_NONE);
            nw = nw->emul64_nwnext) {
                rv = emul64_overlap(&nw->emul64_blocked, blkno, (size_t)count);
        }
        return (rv);
}

/*
 * Operations that do a lot of I/O, such as RAID 5 initializations, result
 * in a CPU bound kernel when the device is an emul64 device.  This makes
 * the machine look hung.  To avoid this problem, give up the CPU from time
 * to time.
 */

static void
emul64_yield_check()
{
        static uint_t   emul64_io_count = 0;    /* # I/Os since last wait */
        static uint_t   emul64_waiting = FALSE; /* TRUE -> a thread is in */
                                                /*   cv_timed wait. */
        clock_t         ticks;

        if (emul64_yield_enable == 0)
                return;

        mutex_enter(&emul64_yield_mutex);

        if (emul64_waiting == TRUE) {
                /*
                 * Another thread has already started the timer.  We'll
                 * just wait here until their time expires, and they
                 * broadcast to us.  When they do that, we'll return and
                 * let our caller do more I/O.
                 */
                cv_wait(&emul64_yield_cv, &emul64_yield_mutex);
        } else if (emul64_io_count++ > emul64_yield_period) {
                /*
                 * Set emul64_waiting to let other threads know that we
                 * have started the timer.
                 */
                emul64_waiting = TRUE;
                emul64_num_delay_called++;
                ticks = drv_usectohz(emul64_yield_length);
                if (ticks == 0)
                        ticks = 1;
                (void) cv_reltimedwait(&emul64_yield_cv, &emul64_yield_mutex,
                    ticks, TR_CLOCK_TICK);
                emul64_io_count = 0;
                emul64_waiting = FALSE;

                /* Broadcast in case others are waiting. */
                cv_broadcast(&emul64_yield_cv);
        }

        mutex_exit(&emul64_yield_mutex);
}