MFC r317848:

[FreeBSD/FreeBSD.git] / sys / cam / scsi / scsi_pass.c

/*-
 * Copyright (c) 1997, 1998, 2000 Justin T. Gibbs.
 * Copyright (c) 1997, 1998, 1999 Kenneth D. Merry.
 * 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,
 *    without modification, immediately at the beginning of the file.
 * 2. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * 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.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/conf.h>
#include <sys/types.h>
#include <sys/bio.h>
#include <sys/bus.h>
#include <sys/devicestat.h>
#include <sys/errno.h>
#include <sys/fcntl.h>
#include <sys/malloc.h>
#include <sys/proc.h>
#include <sys/poll.h>
#include <sys/selinfo.h>
#include <sys/sdt.h>
#include <sys/taskqueue.h>
#include <vm/uma.h>
#include <vm/vm.h>
#include <vm/vm_extern.h>

#include <machine/bus.h>

#include <cam/cam.h>
#include <cam/cam_ccb.h>
#include <cam/cam_periph.h>
#include <cam/cam_queue.h>
#include <cam/cam_xpt.h>
#include <cam/cam_xpt_periph.h>
#include <cam/cam_debug.h>
#include <cam/cam_compat.h>
#include <cam/cam_xpt_periph.h>

#include <cam/scsi/scsi_all.h>
#include <cam/scsi/scsi_pass.h>

typedef enum {
        PASS_FLAG_OPEN                  = 0x01,
        PASS_FLAG_LOCKED                = 0x02,
        PASS_FLAG_INVALID               = 0x04,
        PASS_FLAG_INITIAL_PHYSPATH      = 0x08,
        PASS_FLAG_ZONE_INPROG           = 0x10,
        PASS_FLAG_ZONE_VALID            = 0x20,
        PASS_FLAG_UNMAPPED_CAPABLE      = 0x40,
        PASS_FLAG_ABANDONED_REF_SET     = 0x80
} pass_flags;

typedef enum {
        PASS_STATE_NORMAL
} pass_state;

typedef enum {
        PASS_CCB_BUFFER_IO,
        PASS_CCB_QUEUED_IO
} pass_ccb_types;

#define ccb_type        ppriv_field0
#define ccb_ioreq       ppriv_ptr1

/*
 * The maximum number of memory segments we preallocate.
 */
#define PASS_MAX_SEGS   16

typedef enum {
        PASS_IO_NONE            = 0x00,
        PASS_IO_USER_SEG_MALLOC = 0x01,
        PASS_IO_KERN_SEG_MALLOC = 0x02,
        PASS_IO_ABANDONED       = 0x04
} pass_io_flags; 

struct pass_io_req {
        union ccb                        ccb;
        union ccb                       *alloced_ccb;
        union ccb                       *user_ccb_ptr;
        camq_entry                       user_periph_links;
        ccb_ppriv_area                   user_periph_priv;
        struct cam_periph_map_info       mapinfo;
        pass_io_flags                    flags;
        ccb_flags                        data_flags;
        int                              num_user_segs;
        bus_dma_segment_t                user_segs[PASS_MAX_SEGS];
        int                              num_kern_segs;
        bus_dma_segment_t                kern_segs[PASS_MAX_SEGS];
        bus_dma_segment_t               *user_segptr;
        bus_dma_segment_t               *kern_segptr;
        int                              num_bufs;
        uint32_t                         dirs[CAM_PERIPH_MAXMAPS];
        uint32_t                         lengths[CAM_PERIPH_MAXMAPS];
        uint8_t                         *user_bufs[CAM_PERIPH_MAXMAPS];
        uint8_t                         *kern_bufs[CAM_PERIPH_MAXMAPS];
        struct bintime                   start_time;
        TAILQ_ENTRY(pass_io_req)         links;
};

struct pass_softc {
        pass_state                state;
        pass_flags                flags;
        u_int8_t                  pd_type;
        union ccb                 saved_ccb;
        int                       open_count;
        u_int                     maxio;
        struct devstat           *device_stats;
        struct cdev              *dev;
        struct cdev              *alias_dev;
        struct task               add_physpath_task;
        struct task               shutdown_kqueue_task;
        struct selinfo            read_select;
        TAILQ_HEAD(, pass_io_req) incoming_queue;
        TAILQ_HEAD(, pass_io_req) active_queue;
        TAILQ_HEAD(, pass_io_req) abandoned_queue;
        TAILQ_HEAD(, pass_io_req) done_queue;
        struct cam_periph        *periph;
        char                      zone_name[12];
        char                      io_zone_name[12];
        uma_zone_t                pass_zone;
        uma_zone_t                pass_io_zone;
        size_t                    io_zone_size;
};

static  d_open_t        passopen;
static  d_close_t       passclose;
static  d_ioctl_t       passioctl;
static  d_ioctl_t       passdoioctl;
static  d_poll_t        passpoll;
static  d_kqfilter_t    passkqfilter;
static  void            passreadfiltdetach(struct knote *kn);
static  int             passreadfilt(struct knote *kn, long hint);

static  periph_init_t   passinit;
static  periph_ctor_t   passregister;
static  periph_oninv_t  passoninvalidate;
static  periph_dtor_t   passcleanup;
static  periph_start_t  passstart;
static  void            pass_shutdown_kqueue(void *context, int pending);
static  void            pass_add_physpath(void *context, int pending);
static  void            passasync(void *callback_arg, u_int32_t code,
                                  struct cam_path *path, void *arg);
static  void            passdone(struct cam_periph *periph, 
                                 union ccb *done_ccb);
static  int             passcreatezone(struct cam_periph *periph);
static  void            passiocleanup(struct pass_softc *softc, 
                                      struct pass_io_req *io_req);
static  int             passcopysglist(struct cam_periph *periph,
                                       struct pass_io_req *io_req,
                                       ccb_flags direction);
static  int             passmemsetup(struct cam_periph *periph,
                                     struct pass_io_req *io_req);
static  int             passmemdone(struct cam_periph *periph,
                                    struct pass_io_req *io_req);
static  int             passerror(union ccb *ccb, u_int32_t cam_flags, 
                                  u_int32_t sense_flags);
static  int             passsendccb(struct cam_periph *periph, union ccb *ccb,
                                    union ccb *inccb);

static struct periph_driver passdriver =
{
        passinit, "pass",
        TAILQ_HEAD_INITIALIZER(passdriver.units), /* generation */ 0
};

PERIPHDRIVER_DECLARE(pass, passdriver);

static struct cdevsw pass_cdevsw = {
        .d_version =    D_VERSION,
        .d_flags =      D_TRACKCLOSE,
        .d_open =       passopen,
        .d_close =      passclose,
        .d_ioctl =      passioctl,
        .d_poll =       passpoll,
        .d_kqfilter =   passkqfilter,
        .d_name =       "pass",
};

static struct filterops passread_filtops = {
        .f_isfd =       1,
        .f_detach =     passreadfiltdetach,
        .f_event =      passreadfilt
};

static MALLOC_DEFINE(M_SCSIPASS, "scsi_pass", "scsi passthrough buffers");

static void
passinit(void)
{
        cam_status status;

        /*
         * Install a global async callback.  This callback will
         * receive async callbacks like "new device found".
         */
        status = xpt_register_async(AC_FOUND_DEVICE, passasync, NULL, NULL);

        if (status != CAM_REQ_CMP) {
                printf("pass: Failed to attach master async callback "
                       "due to status 0x%x!\n", status);
        }

}

static void
passrejectios(struct cam_periph *periph)
{
        struct pass_io_req *io_req, *io_req2;
        struct pass_softc *softc;

        softc = (struct pass_softc *)periph->softc;

        /*
         * The user can no longer get status for I/O on the done queue, so
         * clean up all outstanding I/O on the done queue.
         */
        TAILQ_FOREACH_SAFE(io_req, &softc->done_queue, links, io_req2) {
                TAILQ_REMOVE(&softc->done_queue, io_req, links);
                passiocleanup(softc, io_req);
                uma_zfree(softc->pass_zone, io_req);
        }

        /*
         * The underlying device is gone, so we can't issue these I/Os.
         * The devfs node has been shut down, so we can't return status to
         * the user.  Free any I/O left on the incoming queue.
         */
        TAILQ_FOREACH_SAFE(io_req, &softc->incoming_queue, links, io_req2) {
                TAILQ_REMOVE(&softc->incoming_queue, io_req, links);
                passiocleanup(softc, io_req);
                uma_zfree(softc->pass_zone, io_req);
        }

        /*
         * Normally we would put I/Os on the abandoned queue and acquire a
         * reference when we saw the final close.  But, the device went
         * away and devfs may have moved everything off to deadfs by the
         * time the I/O done callback is called; as a result, we won't see
         * any more closes.  So, if we have any active I/Os, we need to put
         * them on the abandoned queue.  When the abandoned queue is empty,
         * we'll release the remaining reference (see below) to the peripheral.
         */
        TAILQ_FOREACH_SAFE(io_req, &softc->active_queue, links, io_req2) {
                TAILQ_REMOVE(&softc->active_queue, io_req, links);
                io_req->flags |= PASS_IO_ABANDONED;
                TAILQ_INSERT_TAIL(&softc->abandoned_queue, io_req, links);
        }

        /*
         * If we put any I/O on the abandoned queue, acquire a reference.
         */
        if ((!TAILQ_EMPTY(&softc->abandoned_queue))
         && ((softc->flags & PASS_FLAG_ABANDONED_REF_SET) == 0)) {
                cam_periph_doacquire(periph);
                softc->flags |= PASS_FLAG_ABANDONED_REF_SET;
        }
}

static void
passdevgonecb(void *arg)
{
        struct cam_periph *periph;
        struct mtx *mtx;
        struct pass_softc *softc;
        int i;

        periph = (struct cam_periph *)arg;
        mtx = cam_periph_mtx(periph);
        mtx_lock(mtx);

        softc = (struct pass_softc *)periph->softc;
        KASSERT(softc->open_count >= 0, ("Negative open count %d",
                softc->open_count));

        /*
         * When we get this callback, we will get no more close calls from
         * devfs.  So if we have any dangling opens, we need to release the
         * reference held for that particular context.
         */
        for (i = 0; i < softc->open_count; i++)
                cam_periph_release_locked(periph);

        softc->open_count = 0;

        /*
         * Release the reference held for the device node, it is gone now.
         * Accordingly, inform all queued I/Os of their fate.
         */
        cam_periph_release_locked(periph);
        passrejectios(periph);

        /*
         * We reference the SIM lock directly here, instead of using
         * cam_periph_unlock().  The reason is that the final call to
         * cam_periph_release_locked() above could result in the periph
         * getting freed.  If that is the case, dereferencing the periph
         * with a cam_periph_unlock() call would cause a page fault.
         */
        mtx_unlock(mtx);

        /*
         * We have to remove our kqueue context from a thread because it
         * may sleep.  It would be nice if we could get a callback from
         * kqueue when it is done cleaning up resources.
         */
        taskqueue_enqueue(taskqueue_thread, &softc->shutdown_kqueue_task);
}

static void
passoninvalidate(struct cam_periph *periph)
{
        struct pass_softc *softc;

        softc = (struct pass_softc *)periph->softc;

        /*
         * De-register any async callbacks.
         */
        xpt_register_async(0, passasync, periph, periph->path);

        softc->flags |= PASS_FLAG_INVALID;

        /*
         * Tell devfs this device has gone away, and ask for a callback
         * when it has cleaned up its state.
         */
        destroy_dev_sched_cb(softc->dev, passdevgonecb, periph);
}

static void
passcleanup(struct cam_periph *periph)
{
        struct pass_softc *softc;

        softc = (struct pass_softc *)periph->softc;

        cam_periph_assert(periph, MA_OWNED);
        KASSERT(TAILQ_EMPTY(&softc->active_queue),
                ("%s called when there are commands on the active queue!\n",
                __func__));
        KASSERT(TAILQ_EMPTY(&softc->abandoned_queue),
                ("%s called when there are commands on the abandoned queue!\n",
                __func__));
        KASSERT(TAILQ_EMPTY(&softc->incoming_queue),
                ("%s called when there are commands on the incoming queue!\n",
                __func__));
        KASSERT(TAILQ_EMPTY(&softc->done_queue),
                ("%s called when there are commands on the done queue!\n",
                __func__));

        devstat_remove_entry(softc->device_stats);

        cam_periph_unlock(periph);

        /*
         * We call taskqueue_drain() for the physpath task to make sure it
         * is complete.  We drop the lock because this can potentially
         * sleep.  XXX KDM that is bad.  Need a way to get a callback when
         * a taskqueue is drained.
         *
         * Note that we don't drain the kqueue shutdown task queue.  This
         * is because we hold a reference on the periph for kqueue, and
         * release that reference from the kqueue shutdown task queue.  So
         * we cannot come into this routine unless we've released that
         * reference.  Also, because that could be the last reference, we
         * could be called from the cam_periph_release() call in
         * pass_shutdown_kqueue().  In that case, the taskqueue_drain()
         * would deadlock.  It would be preferable if we had a way to
         * get a callback when a taskqueue is done.
         */
        taskqueue_drain(taskqueue_thread, &softc->add_physpath_task);

        cam_periph_lock(periph);

        free(softc, M_DEVBUF);
}

static void
pass_shutdown_kqueue(void *context, int pending)
{
        struct cam_periph *periph;
        struct pass_softc *softc;

        periph = context;
        softc = periph->softc;

        knlist_clear(&softc->read_select.si_note, /*is_locked*/ 0);
        knlist_destroy(&softc->read_select.si_note);

        /*
         * Release the reference we held for kqueue.
         */
        cam_periph_release(periph);
}

static void
pass_add_physpath(void *context, int pending)
{
        struct cam_periph *periph;
        struct pass_softc *softc;
        struct mtx *mtx;
        char *physpath;

        /*
         * If we have one, create a devfs alias for our
         * physical path.
         */
        periph = context;
        softc = periph->softc;
        physpath = malloc(MAXPATHLEN, M_DEVBUF, M_WAITOK);
        mtx = cam_periph_mtx(periph);
        mtx_lock(mtx);

        if (periph->flags & CAM_PERIPH_INVALID)
                goto out;

        if (xpt_getattr(physpath, MAXPATHLEN,
                        "GEOM::physpath", periph->path) == 0
         && strlen(physpath) != 0) {

                mtx_unlock(mtx);
                make_dev_physpath_alias(MAKEDEV_WAITOK, &softc->alias_dev,
                                        softc->dev, softc->alias_dev, physpath);
                mtx_lock(mtx);
        }

out:
        /*
         * Now that we've made our alias, we no longer have to have a
         * reference to the device.
         */
        if ((softc->flags & PASS_FLAG_INITIAL_PHYSPATH) == 0)
                softc->flags |= PASS_FLAG_INITIAL_PHYSPATH;

        /*
         * We always acquire a reference to the periph before queueing this
         * task queue function, so it won't go away before we run.
         */
        while (pending-- > 0)
                cam_periph_release_locked(periph);
        mtx_unlock(mtx);

        free(physpath, M_DEVBUF);
}

static void
passasync(void *callback_arg, u_int32_t code,
          struct cam_path *path, void *arg)
{
        struct cam_periph *periph;

        periph = (struct cam_periph *)callback_arg;

        switch (code) {
        case AC_FOUND_DEVICE:
        {
                struct ccb_getdev *cgd;
                cam_status status;
 
                cgd = (struct ccb_getdev *)arg;
                if (cgd == NULL)
                        break;

                /*
                 * Allocate a peripheral instance for
                 * this device and start the probe
                 * process.
                 */
                status = cam_periph_alloc(passregister, passoninvalidate,
                                          passcleanup, passstart, "pass",
                                          CAM_PERIPH_BIO, path,
                                          passasync, AC_FOUND_DEVICE, cgd);

                if (status != CAM_REQ_CMP
                 && status != CAM_REQ_INPROG) {
                        const struct cam_status_entry *entry;

                        entry = cam_fetch_status_entry(status);

                        printf("passasync: Unable to attach new device "
                               "due to status %#x: %s\n", status, entry ?
                               entry->status_text : "Unknown");
                }

                break;
        }
        case AC_ADVINFO_CHANGED:
        {
                uintptr_t buftype;

                buftype = (uintptr_t)arg;
                if (buftype == CDAI_TYPE_PHYS_PATH) {
                        struct pass_softc *softc;
                        cam_status status;

                        softc = (struct pass_softc *)periph->softc;
                        /*
                         * Acquire a reference to the periph before we
                         * start the taskqueue, so that we don't run into
                         * a situation where the periph goes away before
                         * the task queue has a chance to run.
                         */
                        status = cam_periph_acquire(periph);
                        if (status != CAM_REQ_CMP)
                                break;

                        taskqueue_enqueue(taskqueue_thread,
                                          &softc->add_physpath_task);
                }
                break;
        }
        default:
                cam_periph_async(periph, code, path, arg);
                break;
        }
}

static cam_status
passregister(struct cam_periph *periph, void *arg)
{
        struct pass_softc *softc;
        struct ccb_getdev *cgd;
        struct ccb_pathinq cpi;
        struct make_dev_args args;
        int error, no_tags;

        cgd = (struct ccb_getdev *)arg;
        if (cgd == NULL) {
                printf("%s: no getdev CCB, can't register device\n", __func__);
                return(CAM_REQ_CMP_ERR);
        }

        softc = (struct pass_softc *)malloc(sizeof(*softc),
                                            M_DEVBUF, M_NOWAIT);

        if (softc == NULL) {
                printf("%s: Unable to probe new device. "
                       "Unable to allocate softc\n", __func__);
                return(CAM_REQ_CMP_ERR);
        }

        bzero(softc, sizeof(*softc));
        softc->state = PASS_STATE_NORMAL;
        if (cgd->protocol == PROTO_SCSI || cgd->protocol == PROTO_ATAPI)
                softc->pd_type = SID_TYPE(&cgd->inq_data);
        else if (cgd->protocol == PROTO_SATAPM)
                softc->pd_type = T_ENCLOSURE;
        else
                softc->pd_type = T_DIRECT;

        periph->softc = softc;
        softc->periph = periph;
        TAILQ_INIT(&softc->incoming_queue);
        TAILQ_INIT(&softc->active_queue);
        TAILQ_INIT(&softc->abandoned_queue);
        TAILQ_INIT(&softc->done_queue);
        snprintf(softc->zone_name, sizeof(softc->zone_name), "%s%d",
                 periph->periph_name, periph->unit_number);
        snprintf(softc->io_zone_name, sizeof(softc->io_zone_name), "%s%dIO",
                 periph->periph_name, periph->unit_number);
        softc->io_zone_size = MAXPHYS;
        knlist_init_mtx(&softc->read_select.si_note, cam_periph_mtx(periph));

        bzero(&cpi, sizeof(cpi));
        xpt_setup_ccb(&cpi.ccb_h, periph->path, CAM_PRIORITY_NORMAL);
        cpi.ccb_h.func_code = XPT_PATH_INQ;
        xpt_action((union ccb *)&cpi);

        if (cpi.maxio == 0)
                softc->maxio = DFLTPHYS;        /* traditional default */
        else if (cpi.maxio > MAXPHYS)
                softc->maxio = MAXPHYS;         /* for safety */
        else
                softc->maxio = cpi.maxio;       /* real value */

        if (cpi.hba_misc & PIM_UNMAPPED)
                softc->flags |= PASS_FLAG_UNMAPPED_CAPABLE;

        /*
         * We pass in 0 for a blocksize, since we don't 
         * know what the blocksize of this device is, if 
         * it even has a blocksize.
         */
        cam_periph_unlock(periph);
        no_tags = (cgd->inq_data.flags & SID_CmdQue) == 0;
        softc->device_stats = devstat_new_entry("pass",
                          periph->unit_number, 0,
                          DEVSTAT_NO_BLOCKSIZE
                          | (no_tags ? DEVSTAT_NO_ORDERED_TAGS : 0),
                          softc->pd_type |
                          XPORT_DEVSTAT_TYPE(cpi.transport) |
                          DEVSTAT_TYPE_PASS,
                          DEVSTAT_PRIORITY_PASS);

        /*
         * Initialize the taskqueue handler for shutting down kqueue.
         */
        TASK_INIT(&softc->shutdown_kqueue_task, /*priority*/ 0,
                  pass_shutdown_kqueue, periph);

        /*
         * Acquire a reference to the periph that we can release once we've
         * cleaned up the kqueue.
         */
        if (cam_periph_acquire(periph) != CAM_REQ_CMP) {
                xpt_print(periph->path, "%s: lost periph during "
                          "registration!\n", __func__);
                cam_periph_lock(periph);
                return (CAM_REQ_CMP_ERR);
        }

        /*
         * Acquire a reference to the periph before we create the devfs
         * instance for it.  We'll release this reference once the devfs
         * instance has been freed.
         */
        if (cam_periph_acquire(periph) != CAM_REQ_CMP) {
                xpt_print(periph->path, "%s: lost periph during "
                          "registration!\n", __func__);
                cam_periph_lock(periph);
                return (CAM_REQ_CMP_ERR);
        }

        /* Register the device */
        make_dev_args_init(&args);
        args.mda_devsw = &pass_cdevsw;
        args.mda_unit = periph->unit_number;
        args.mda_uid = UID_ROOT;
        args.mda_gid = GID_OPERATOR;
        args.mda_mode = 0600;
        args.mda_si_drv1 = periph;
        error = make_dev_s(&args, &softc->dev, "%s%d", periph->periph_name,
            periph->unit_number);
        if (error != 0) {
                cam_periph_lock(periph);
                cam_periph_release_locked(periph);
                return (CAM_REQ_CMP_ERR);
        }

        /*
         * Hold a reference to the periph before we create the physical
         * path alias so it can't go away.
         */
        if (cam_periph_acquire(periph) != CAM_REQ_CMP) {
                xpt_print(periph->path, "%s: lost periph during "
                          "registration!\n", __func__);
                cam_periph_lock(periph);
                return (CAM_REQ_CMP_ERR);
        }

        cam_periph_lock(periph);

        TASK_INIT(&softc->add_physpath_task, /*priority*/0,
                  pass_add_physpath, periph);

        /*
         * See if physical path information is already available.
         */
        taskqueue_enqueue(taskqueue_thread, &softc->add_physpath_task);

        /*
         * Add an async callback so that we get notified if
         * this device goes away or its physical path
         * (stored in the advanced info data of the EDT) has
         * changed.
         */
        xpt_register_async(AC_LOST_DEVICE | AC_ADVINFO_CHANGED,
                           passasync, periph, periph->path);

        if (bootverbose)
                xpt_announce_periph(periph, NULL);

        return(CAM_REQ_CMP);
}

static int
passopen(struct cdev *dev, int flags, int fmt, struct thread *td)
{
        struct cam_periph *periph;
        struct pass_softc *softc;
        int error;

        periph = (struct cam_periph *)dev->si_drv1;
        if (cam_periph_acquire(periph) != CAM_REQ_CMP)
                return (ENXIO);

        cam_periph_lock(periph);

        softc = (struct pass_softc *)periph->softc;

        if (softc->flags & PASS_FLAG_INVALID) {
                cam_periph_release_locked(periph);
                cam_periph_unlock(periph);
                return(ENXIO);
        }

        /*
         * Don't allow access when we're running at a high securelevel.
         */
        error = securelevel_gt(td->td_ucred, 1);
        if (error) {
                cam_periph_release_locked(periph);
                cam_periph_unlock(periph);
                return(error);
        }

        /*
         * Only allow read-write access.
         */
        if (((flags & FWRITE) == 0) || ((flags & FREAD) == 0)) {
                cam_periph_release_locked(periph);
                cam_periph_unlock(periph);
                return(EPERM);
        }

        /*
         * We don't allow nonblocking access.
         */
        if ((flags & O_NONBLOCK) != 0) {
                xpt_print(periph->path, "can't do nonblocking access\n");
                cam_periph_release_locked(periph);
                cam_periph_unlock(periph);
                return(EINVAL);
        }

        softc->open_count++;

        cam_periph_unlock(periph);

        return (error);
}

static int
passclose(struct cdev *dev, int flag, int fmt, struct thread *td)
{
        struct  cam_periph *periph;
        struct  pass_softc *softc;
        struct mtx *mtx;

        periph = (struct cam_periph *)dev->si_drv1;
        mtx = cam_periph_mtx(periph);
        mtx_lock(mtx);

        softc = periph->softc;
        softc->open_count--;

        if (softc->open_count == 0) {
                struct pass_io_req *io_req, *io_req2;

                TAILQ_FOREACH_SAFE(io_req, &softc->done_queue, links, io_req2) {
                        TAILQ_REMOVE(&softc->done_queue, io_req, links);
                        passiocleanup(softc, io_req);
                        uma_zfree(softc->pass_zone, io_req);
                }

                TAILQ_FOREACH_SAFE(io_req, &softc->incoming_queue, links,
                                   io_req2) {
                        TAILQ_REMOVE(&softc->incoming_queue, io_req, links);
                        passiocleanup(softc, io_req);
                        uma_zfree(softc->pass_zone, io_req);
                }

                /*
                 * If there are any active I/Os, we need to forcibly acquire a
                 * reference to the peripheral so that we don't go away
                 * before they complete.  We'll release the reference when
                 * the abandoned queue is empty.
                 */
                io_req = TAILQ_FIRST(&softc->active_queue);
                if ((io_req != NULL)
                 && (softc->flags & PASS_FLAG_ABANDONED_REF_SET) == 0) {
                        cam_periph_doacquire(periph);
                        softc->flags |= PASS_FLAG_ABANDONED_REF_SET;
                }

                /*
                 * Since the I/O in the active queue is not under our
                 * control, just set a flag so that we can clean it up when
                 * it completes and put it on the abandoned queue.  This
                 * will prevent our sending spurious completions in the
                 * event that the device is opened again before these I/Os
                 * complete.
                 */
                TAILQ_FOREACH_SAFE(io_req, &softc->active_queue, links,
                                   io_req2) {
                        TAILQ_REMOVE(&softc->active_queue, io_req, links);
                        io_req->flags |= PASS_IO_ABANDONED;
                        TAILQ_INSERT_TAIL(&softc->abandoned_queue, io_req,
                                          links);
                }
        }

        cam_periph_release_locked(periph);

        /*
         * We reference the lock directly here, instead of using
         * cam_periph_unlock().  The reason is that the call to
         * cam_periph_release_locked() above could result in the periph
         * getting freed.  If that is the case, dereferencing the periph
         * with a cam_periph_unlock() call would cause a page fault.
         *
         * cam_periph_release() avoids this problem using the same method,
         * but we're manually acquiring and dropping the lock here to
         * protect the open count and avoid another lock acquisition and
         * release.
         */
        mtx_unlock(mtx);

        return (0);
}


static void
passstart(struct cam_periph *periph, union ccb *start_ccb)
{
        struct pass_softc *softc;

        softc = (struct pass_softc *)periph->softc;

        switch (softc->state) {
        case PASS_STATE_NORMAL: {
                struct pass_io_req *io_req;

                /*
                 * Check for any queued I/O requests that require an
                 * allocated slot.
                 */
                io_req = TAILQ_FIRST(&softc->incoming_queue);
                if (io_req == NULL) {
                        xpt_release_ccb(start_ccb);
                        break;
                }
                TAILQ_REMOVE(&softc->incoming_queue, io_req, links);
                TAILQ_INSERT_TAIL(&softc->active_queue, io_req, links);
                /*
                 * Merge the user's CCB into the allocated CCB.
                 */
                xpt_merge_ccb(start_ccb, &io_req->ccb);
                start_ccb->ccb_h.ccb_type = PASS_CCB_QUEUED_IO;
                start_ccb->ccb_h.ccb_ioreq = io_req;
                start_ccb->ccb_h.cbfcnp = passdone;
                io_req->alloced_ccb = start_ccb;
                binuptime(&io_req->start_time);
                devstat_start_transaction(softc->device_stats,
                                          &io_req->start_time);

                xpt_action(start_ccb);

                /*
                 * If we have any more I/O waiting, schedule ourselves again.
                 */
                if (!TAILQ_EMPTY(&softc->incoming_queue))
                        xpt_schedule(periph, CAM_PRIORITY_NORMAL);
                break;
        }
        default:
                break;
        }
}

static void
passdone(struct cam_periph *periph, union ccb *done_ccb)
{ 
        struct pass_softc *softc;
        struct ccb_scsiio *csio;

        softc = (struct pass_softc *)periph->softc;

        cam_periph_assert(periph, MA_OWNED);

        csio = &done_ccb->csio;
        switch (csio->ccb_h.ccb_type) {
        case PASS_CCB_QUEUED_IO: {
                struct pass_io_req *io_req;

                io_req = done_ccb->ccb_h.ccb_ioreq;
#if 0
                xpt_print(periph->path, "%s: called for user CCB %p\n",
                          __func__, io_req->user_ccb_ptr);
#endif
                if (((done_ccb->ccb_h.status & CAM_STATUS_MASK) != CAM_REQ_CMP)
                 && (done_ccb->ccb_h.flags & CAM_PASS_ERR_RECOVER)
                 && ((io_req->flags & PASS_IO_ABANDONED) == 0)) {
                        int error;

                        error = passerror(done_ccb, CAM_RETRY_SELTO,
                                          SF_RETRY_UA | SF_NO_PRINT);

                        if (error == ERESTART) {
                                /*
                                 * A retry was scheduled, so
                                 * just return.
                                 */
                                return;
                        }
                }

                /*
                 * Copy the allocated CCB contents back to the malloced CCB
                 * so we can give status back to the user when he requests it.
                 */
                bcopy(done_ccb, &io_req->ccb, sizeof(*done_ccb));

                /*
                 * Log data/transaction completion with devstat(9).
                 */
                switch (done_ccb->ccb_h.func_code) {
                case XPT_SCSI_IO:
                        devstat_end_transaction(softc->device_stats,
                            done_ccb->csio.dxfer_len - done_ccb->csio.resid,
                            done_ccb->csio.tag_action & 0x3,
                            ((done_ccb->ccb_h.flags & CAM_DIR_MASK) ==
                            CAM_DIR_NONE) ? DEVSTAT_NO_DATA :
                            (done_ccb->ccb_h.flags & CAM_DIR_OUT) ?
                            DEVSTAT_WRITE : DEVSTAT_READ, NULL,
                            &io_req->start_time);
                        break;
                case XPT_ATA_IO:
                        devstat_end_transaction(softc->device_stats,
                            done_ccb->ataio.dxfer_len - done_ccb->ataio.resid,
                            0, /* Not used in ATA */
                            ((done_ccb->ccb_h.flags & CAM_DIR_MASK) ==
                            CAM_DIR_NONE) ? DEVSTAT_NO_DATA : 
                            (done_ccb->ccb_h.flags & CAM_DIR_OUT) ?
                            DEVSTAT_WRITE : DEVSTAT_READ, NULL,
                            &io_req->start_time);
                        break;
                case XPT_SMP_IO:
                        /*
                         * XXX KDM this isn't quite right, but there isn't
                         * currently an easy way to represent a bidirectional 
                         * transfer in devstat.  The only way to do it
                         * and have the byte counts come out right would
                         * mean that we would have to record two
                         * transactions, one for the request and one for the
                         * response.  For now, so that we report something,
                         * just treat the entire thing as a read.
                         */
                        devstat_end_transaction(softc->device_stats,
                            done_ccb->smpio.smp_request_len +
                            done_ccb->smpio.smp_response_len,
                            DEVSTAT_TAG_SIMPLE, DEVSTAT_READ, NULL,
                            &io_req->start_time);
                        break;
                default:
                        devstat_end_transaction(softc->device_stats, 0,
                            DEVSTAT_TAG_NONE, DEVSTAT_NO_DATA, NULL,
                            &io_req->start_time);
                        break;
                }

                /*
                 * In the normal case, take the completed I/O off of the
                 * active queue and put it on the done queue.  Notitfy the
                 * user that we have a completed I/O.
                 */
                if ((io_req->flags & PASS_IO_ABANDONED) == 0) {
                        TAILQ_REMOVE(&softc->active_queue, io_req, links);
                        TAILQ_INSERT_TAIL(&softc->done_queue, io_req, links);
                        selwakeuppri(&softc->read_select, PRIBIO);
                        KNOTE_LOCKED(&softc->read_select.si_note, 0);
                } else {
                        /*
                         * In the case of an abandoned I/O (final close
                         * without fetching the I/O), take it off of the
                         * abandoned queue and free it.
                         */
                        TAILQ_REMOVE(&softc->abandoned_queue, io_req, links);
                        passiocleanup(softc, io_req);
                        uma_zfree(softc->pass_zone, io_req);

                        /*
                         * Release the done_ccb here, since we may wind up
                         * freeing the peripheral when we decrement the
                         * reference count below.
                         */
                        xpt_release_ccb(done_ccb);

                        /*
                         * If the abandoned queue is empty, we can release
                         * our reference to the periph since we won't have
                         * any more completions coming.
                         */
                        if ((TAILQ_EMPTY(&softc->abandoned_queue))
                         && (softc->flags & PASS_FLAG_ABANDONED_REF_SET)) {
                                softc->flags &= ~PASS_FLAG_ABANDONED_REF_SET;
                                cam_periph_release_locked(periph);
                        }

                        /*
                         * We have already released the CCB, so we can
                         * return.
                         */
                        return;
                }
                break;
        }
        }
        xpt_release_ccb(done_ccb);
}

static int
passcreatezone(struct cam_periph *periph)
{
        struct pass_softc *softc;
        int error;

        error = 0;
        softc = (struct pass_softc *)periph->softc;

        cam_periph_assert(periph, MA_OWNED);
        KASSERT(((softc->flags & PASS_FLAG_ZONE_VALID) == 0), 
                ("%s called when the pass(4) zone is valid!\n", __func__));
        KASSERT((softc->pass_zone == NULL), 
                ("%s called when the pass(4) zone is allocated!\n", __func__));

        if ((softc->flags & PASS_FLAG_ZONE_INPROG) == 0) {

                /*
                 * We're the first context through, so we need to create
                 * the pass(4) UMA zone for I/O requests.
                 */
                softc->flags |= PASS_FLAG_ZONE_INPROG;

                /*
                 * uma_zcreate() does a blocking (M_WAITOK) allocation,
                 * so we cannot hold a mutex while we call it.
                 */
                cam_periph_unlock(periph);

                softc->pass_zone = uma_zcreate(softc->zone_name,
                    sizeof(struct pass_io_req), NULL, NULL, NULL, NULL,
                    /*align*/ 0, /*flags*/ 0);

                softc->pass_io_zone = uma_zcreate(softc->io_zone_name,
                    softc->io_zone_size, NULL, NULL, NULL, NULL,
                    /*align*/ 0, /*flags*/ 0);

                cam_periph_lock(periph);

                if ((softc->pass_zone == NULL)
                 || (softc->pass_io_zone == NULL)) {
                        if (softc->pass_zone == NULL)
                                xpt_print(periph->path, "unable to allocate "
                                    "IO Req UMA zone\n");
                        else
                                xpt_print(periph->path, "unable to allocate "
                                    "IO UMA zone\n");
                        softc->flags &= ~PASS_FLAG_ZONE_INPROG;
                        goto bailout;
                }

                /*
                 * Set the flags appropriately and notify any other waiters.
                 */
                softc->flags &= PASS_FLAG_ZONE_INPROG;
                softc->flags |= PASS_FLAG_ZONE_VALID;
                wakeup(&softc->pass_zone);
        } else {
                /*
                 * In this case, the UMA zone has not yet been created, but
                 * another context is in the process of creating it.  We
                 * need to sleep until the creation is either done or has
                 * failed.
                 */
                while ((softc->flags & PASS_FLAG_ZONE_INPROG)
                    && ((softc->flags & PASS_FLAG_ZONE_VALID) == 0)) {
                        error = msleep(&softc->pass_zone,
                                       cam_periph_mtx(periph), PRIBIO,
                                       "paszon", 0);
                        if (error != 0)
                                goto bailout;
                }
                /*
                 * If the zone creation failed, no luck for the user.
                 */
                if ((softc->flags & PASS_FLAG_ZONE_VALID) == 0){
                        error = ENOMEM;
                        goto bailout;
                }
        }
bailout:
        return (error);
}

static void
passiocleanup(struct pass_softc *softc, struct pass_io_req *io_req)
{
        union ccb *ccb;
        u_int8_t **data_ptrs[CAM_PERIPH_MAXMAPS];
        int i, numbufs;

        ccb = &io_req->ccb;

        switch (ccb->ccb_h.func_code) {
        case XPT_DEV_MATCH:
                numbufs = min(io_req->num_bufs, 2);

                if (numbufs == 1) {
                        data_ptrs[0] = (u_int8_t **)&ccb->cdm.matches;
                } else {
                        data_ptrs[0] = (u_int8_t **)&ccb->cdm.patterns;
                        data_ptrs[1] = (u_int8_t **)&ccb->cdm.matches;
                }
                break;
        case XPT_SCSI_IO:
        case XPT_CONT_TARGET_IO:
                data_ptrs[0] = &ccb->csio.data_ptr;
                numbufs = min(io_req->num_bufs, 1);
                break;
        case XPT_ATA_IO:
                data_ptrs[0] = &ccb->ataio.data_ptr;
                numbufs = min(io_req->num_bufs, 1);
                break;
        case XPT_SMP_IO:
                numbufs = min(io_req->num_bufs, 2);
                data_ptrs[0] = &ccb->smpio.smp_request;
                data_ptrs[1] = &ccb->smpio.smp_response;
                break;
        case XPT_DEV_ADVINFO:
                numbufs = min(io_req->num_bufs, 1);
                data_ptrs[0] = (uint8_t **)&ccb->cdai.buf;
                break;
        default:
                /* allow ourselves to be swapped once again */
                return;
                break; /* NOTREACHED */ 
        }

        if (io_req->flags & PASS_IO_USER_SEG_MALLOC) {
                free(io_req->user_segptr, M_SCSIPASS);
                io_req->user_segptr = NULL;
        }

        /*
         * We only want to free memory we malloced.
         */
        if (io_req->data_flags == CAM_DATA_VADDR) {
                for (i = 0; i < io_req->num_bufs; i++) {
                        if (io_req->kern_bufs[i] == NULL)
                                continue;

                        free(io_req->kern_bufs[i], M_SCSIPASS);
                        io_req->kern_bufs[i] = NULL;
                }
        } else if (io_req->data_flags == CAM_DATA_SG) {
                for (i = 0; i < io_req->num_kern_segs; i++) {
                        if ((uint8_t *)(uintptr_t)
                            io_req->kern_segptr[i].ds_addr == NULL)
                                continue;

                        uma_zfree(softc->pass_io_zone, (uint8_t *)(uintptr_t)
                            io_req->kern_segptr[i].ds_addr);
                        io_req->kern_segptr[i].ds_addr = 0;
                }
        }

        if (io_req->flags & PASS_IO_KERN_SEG_MALLOC) {
                free(io_req->kern_segptr, M_SCSIPASS);
                io_req->kern_segptr = NULL;
        }

        if (io_req->data_flags != CAM_DATA_PADDR) {
                for (i = 0; i < numbufs; i++) {
                        /*
                         * Restore the user's buffer pointers to their
                         * previous values.
                         */
                        if (io_req->user_bufs[i] != NULL)
                                *data_ptrs[i] = io_req->user_bufs[i];
                }
        }

}

static int
passcopysglist(struct cam_periph *periph, struct pass_io_req *io_req,
               ccb_flags direction)
{
        bus_size_t kern_watermark, user_watermark, len_copied, len_to_copy;
        bus_dma_segment_t *user_sglist, *kern_sglist;
        int i, j, error;

        error = 0;
        kern_watermark = 0;
        user_watermark = 0;
        len_to_copy = 0;
        len_copied = 0;
        user_sglist = io_req->user_segptr;
        kern_sglist = io_req->kern_segptr;

        for (i = 0, j = 0; i < io_req->num_user_segs &&
             j < io_req->num_kern_segs;) {
                uint8_t *user_ptr, *kern_ptr;

                len_to_copy = min(user_sglist[i].ds_len -user_watermark,
                    kern_sglist[j].ds_len - kern_watermark);

                user_ptr = (uint8_t *)(uintptr_t)user_sglist[i].ds_addr;
                user_ptr = user_ptr + user_watermark;
                kern_ptr = (uint8_t *)(uintptr_t)kern_sglist[j].ds_addr;
                kern_ptr = kern_ptr + kern_watermark;

                user_watermark += len_to_copy;
                kern_watermark += len_to_copy;

                if (!useracc(user_ptr, len_to_copy,
                    (direction == CAM_DIR_IN) ? VM_PROT_WRITE : VM_PROT_READ)) {
                        xpt_print(periph->path, "%s: unable to access user "
                                  "S/G list element %p len %zu\n", __func__,
                                  user_ptr, len_to_copy);
                        error = EFAULT;
                        goto bailout;
                }

                if (direction == CAM_DIR_IN) {
                        error = copyout(kern_ptr, user_ptr, len_to_copy);
                        if (error != 0) {
                                xpt_print(periph->path, "%s: copyout of %u "
                                          "bytes from %p to %p failed with "
                                          "error %d\n", __func__, len_to_copy,
                                          kern_ptr, user_ptr, error);
                                goto bailout;
                        }
                } else {
                        error = copyin(user_ptr, kern_ptr, len_to_copy);
                        if (error != 0) {
                                xpt_print(periph->path, "%s: copyin of %u "
                                          "bytes from %p to %p failed with "
                                          "error %d\n", __func__, len_to_copy,
                                          user_ptr, kern_ptr, error);
                                goto bailout;
                        }
                }

                len_copied += len_to_copy;

                if (user_sglist[i].ds_len == user_watermark) {
                        i++;
                        user_watermark = 0;
                }

                if (kern_sglist[j].ds_len == kern_watermark) {
                        j++;
                        kern_watermark = 0;
                }
        }

bailout:

        return (error);
}

static int
passmemsetup(struct cam_periph *periph, struct pass_io_req *io_req)
{
        union ccb *ccb;
        struct pass_softc *softc;
        int numbufs, i;
        uint8_t **data_ptrs[CAM_PERIPH_MAXMAPS];
        uint32_t lengths[CAM_PERIPH_MAXMAPS];
        uint32_t dirs[CAM_PERIPH_MAXMAPS];
        uint32_t num_segs;
        uint16_t *seg_cnt_ptr;
        size_t maxmap;
        int error;

        cam_periph_assert(periph, MA_NOTOWNED);

        softc = periph->softc;

        error = 0;
        ccb = &io_req->ccb;
        maxmap = 0;
        num_segs = 0;
        seg_cnt_ptr = NULL;

        switch(ccb->ccb_h.func_code) {
        case XPT_DEV_MATCH:
                if (ccb->cdm.match_buf_len == 0) {
                        printf("%s: invalid match buffer length 0\n", __func__);
                        return(EINVAL);
                }
                if (ccb->cdm.pattern_buf_len > 0) {
                        data_ptrs[0] = (u_int8_t **)&ccb->cdm.patterns;
                        lengths[0] = ccb->cdm.pattern_buf_len;
                        dirs[0] = CAM_DIR_OUT;
                        data_ptrs[1] = (u_int8_t **)&ccb->cdm.matches;
                        lengths[1] = ccb->cdm.match_buf_len;
                        dirs[1] = CAM_DIR_IN;
                        numbufs = 2;
                } else {
                        data_ptrs[0] = (u_int8_t **)&ccb->cdm.matches;
                        lengths[0] = ccb->cdm.match_buf_len;
                        dirs[0] = CAM_DIR_IN;
                        numbufs = 1;
                }
                io_req->data_flags = CAM_DATA_VADDR;
                break;
        case XPT_SCSI_IO:
        case XPT_CONT_TARGET_IO:
                if ((ccb->ccb_h.flags & CAM_DIR_MASK) == CAM_DIR_NONE)
                        return(0);

                /*
                 * The user shouldn't be able to supply a bio.
                 */
                if ((ccb->ccb_h.flags & CAM_DATA_MASK) == CAM_DATA_BIO)
                        return (EINVAL);

                io_req->data_flags = ccb->ccb_h.flags & CAM_DATA_MASK;

                data_ptrs[0] = &ccb->csio.data_ptr;
                lengths[0] = ccb->csio.dxfer_len;
                dirs[0] = ccb->ccb_h.flags & CAM_DIR_MASK;
                num_segs = ccb->csio.sglist_cnt;
                seg_cnt_ptr = &ccb->csio.sglist_cnt;
                numbufs = 1;
                maxmap = softc->maxio;
                break;
        case XPT_ATA_IO:
                if ((ccb->ccb_h.flags & CAM_DIR_MASK) == CAM_DIR_NONE)
                        return(0);

                /*
                 * We only support a single virtual address for ATA I/O.
                 */
                if ((ccb->ccb_h.flags & CAM_DATA_MASK) != CAM_DATA_VADDR)
                        return (EINVAL);

                io_req->data_flags = CAM_DATA_VADDR;

                data_ptrs[0] = &ccb->ataio.data_ptr;
                lengths[0] = ccb->ataio.dxfer_len;
                dirs[0] = ccb->ccb_h.flags & CAM_DIR_MASK;
                numbufs = 1;
                maxmap = softc->maxio;
                break;
        case XPT_SMP_IO:
                io_req->data_flags = CAM_DATA_VADDR;

                data_ptrs[0] = &ccb->smpio.smp_request;
                lengths[0] = ccb->smpio.smp_request_len;
                dirs[0] = CAM_DIR_OUT;
                data_ptrs[1] = &ccb->smpio.smp_response;
                lengths[1] = ccb->smpio.smp_response_len;
                dirs[1] = CAM_DIR_IN;
                numbufs = 2;
                maxmap = softc->maxio;
                break;
        case XPT_DEV_ADVINFO:
                if (ccb->cdai.bufsiz == 0)
                        return (0);

                io_req->data_flags = CAM_DATA_VADDR;

                data_ptrs[0] = (uint8_t **)&ccb->cdai.buf;
                lengths[0] = ccb->cdai.bufsiz;
                dirs[0] = CAM_DIR_IN;
                numbufs = 1;
                break;
        default:
                return(EINVAL);
                break; /* NOTREACHED */
        }

        io_req->num_bufs = numbufs;

        /*
         * If there is a maximum, check to make sure that the user's
         * request fits within the limit.  In general, we should only have
         * a maximum length for requests that go to hardware.  Otherwise it
         * is whatever we're able to malloc.
         */
        for (i = 0; i < numbufs; i++) {
                io_req->user_bufs[i] = *data_ptrs[i];
                io_req->dirs[i] = dirs[i];
                io_req->lengths[i] = lengths[i];

                if (maxmap == 0)
                        continue;

                if (lengths[i] <= maxmap)
                        continue;

                xpt_print(periph->path, "%s: data length %u > max allowed %u "
                          "bytes\n", __func__, lengths[i], maxmap);
                error = EINVAL;
                goto bailout;
        }

        switch (io_req->data_flags) {
        case CAM_DATA_VADDR:
                /* Map or copy the buffer into kernel address space */
                for (i = 0; i < numbufs; i++) {
                        uint8_t *tmp_buf;

                        /*
                         * If for some reason no length is specified, we
                         * don't need to allocate anything.
                         */
                        if (io_req->lengths[i] == 0)
                                continue;

                        /*
                         * Make sure that the user's buffer is accessible
                         * to that process.
                         */
                        if (!useracc(io_req->user_bufs[i], io_req->lengths[i],
                            (io_req->dirs[i] == CAM_DIR_IN) ? VM_PROT_WRITE :
                             VM_PROT_READ)) {
                                xpt_print(periph->path, "%s: user address %p "
                                    "length %u is not accessible\n", __func__,
                                    io_req->user_bufs[i], io_req->lengths[i]);
                                error = EFAULT;
                                goto bailout;
                        }

                        tmp_buf = malloc(lengths[i], M_SCSIPASS,
                                         M_WAITOK | M_ZERO);
                        io_req->kern_bufs[i] = tmp_buf;
                        *data_ptrs[i] = tmp_buf;

#if 0
                        xpt_print(periph->path, "%s: malloced %p len %u, user "
                                  "buffer %p, operation: %s\n", __func__,
                                  tmp_buf, lengths[i], io_req->user_bufs[i],
                                  (dirs[i] == CAM_DIR_IN) ? "read" : "write");
#endif
                        /*
                         * We only need to copy in if the user is writing.
                         */
                        if (dirs[i] != CAM_DIR_OUT)
                                continue;

                        error = copyin(io_req->user_bufs[i],
                                       io_req->kern_bufs[i], lengths[i]);
                        if (error != 0) {
                                xpt_print(periph->path, "%s: copy of user "
                                          "buffer from %p to %p failed with "
                                          "error %d\n", __func__,
                                          io_req->user_bufs[i],
                                          io_req->kern_bufs[i], error);
                                goto bailout;
                        }
                }
                break;
        case CAM_DATA_PADDR:
                /* Pass down the pointer as-is */
                break;
        case CAM_DATA_SG: {
                size_t sg_length, size_to_go, alloc_size;
                uint32_t num_segs_needed;

                /*
                 * Copy the user S/G list in, and then copy in the
                 * individual segments.
                 */
                /*
                 * We shouldn't see this, but check just in case.
                 */
                if (numbufs != 1) {
                        xpt_print(periph->path, "%s: cannot currently handle "
                                  "more than one S/G list per CCB\n", __func__);
                        error = EINVAL;
                        goto bailout;
                }

                /*
                 * We have to have at least one segment.
                 */
                if (num_segs == 0) {
                        xpt_print(periph->path, "%s: CAM_DATA_SG flag set, "
                                  "but sglist_cnt=0!\n", __func__);
                        error = EINVAL;
                        goto bailout;
                }

                /*
                 * Make sure the user specified the total length and didn't
                 * just leave it to us to decode the S/G list.
                 */
                if (lengths[0] == 0) {
                        xpt_print(periph->path, "%s: no dxfer_len specified, "
                                  "but CAM_DATA_SG flag is set!\n", __func__);
                        error = EINVAL;
                        goto bailout;
                }

                /*
                 * We allocate buffers in io_zone_size increments for an
                 * S/G list.  This will generally be MAXPHYS.
                 */
                if (lengths[0] <= softc->io_zone_size)
                        num_segs_needed = 1;
                else {
                        num_segs_needed = lengths[0] / softc->io_zone_size;
                        if ((lengths[0] % softc->io_zone_size) != 0)
                                num_segs_needed++;
                }

                /* Figure out the size of the S/G list */
                sg_length = num_segs * sizeof(bus_dma_segment_t);
                io_req->num_user_segs = num_segs;
                io_req->num_kern_segs = num_segs_needed;

                /* Save the user's S/G list pointer for later restoration */
                io_req->user_bufs[0] = *data_ptrs[0];

                /*
                 * If we have enough segments allocated by default to handle
                 * the length of the user's S/G list,
                 */
                if (num_segs > PASS_MAX_SEGS) {
                        io_req->user_segptr = malloc(sizeof(bus_dma_segment_t) *
                            num_segs, M_SCSIPASS, M_WAITOK | M_ZERO);
                        io_req->flags |= PASS_IO_USER_SEG_MALLOC;
                } else
                        io_req->user_segptr = io_req->user_segs;

                if (!useracc(*data_ptrs[0], sg_length, VM_PROT_READ)) {
                        xpt_print(periph->path, "%s: unable to access user "
                                  "S/G list at %p\n", __func__, *data_ptrs[0]);
                        error = EFAULT;
                        goto bailout;
                }

                error = copyin(*data_ptrs[0], io_req->user_segptr, sg_length);
                if (error != 0) {
                        xpt_print(periph->path, "%s: copy of user S/G list "
                                  "from %p to %p failed with error %d\n",
                                  __func__, *data_ptrs[0], io_req->user_segptr,
                                  error);
                        goto bailout;
                }

                if (num_segs_needed > PASS_MAX_SEGS) {
                        io_req->kern_segptr = malloc(sizeof(bus_dma_segment_t) *
                            num_segs_needed, M_SCSIPASS, M_WAITOK | M_ZERO);
                        io_req->flags |= PASS_IO_KERN_SEG_MALLOC;
                } else {
                        io_req->kern_segptr = io_req->kern_segs;
                }

                /*
                 * Allocate the kernel S/G list.
                 */
                for (size_to_go = lengths[0], i = 0;
                     size_to_go > 0 && i < num_segs_needed;
                     i++, size_to_go -= alloc_size) {
                        uint8_t *kern_ptr;

                        alloc_size = min(size_to_go, softc->io_zone_size);
                        kern_ptr = uma_zalloc(softc->pass_io_zone, M_WAITOK);
                        io_req->kern_segptr[i].ds_addr =
                            (bus_addr_t)(uintptr_t)kern_ptr;
                        io_req->kern_segptr[i].ds_len = alloc_size;
                }
                if (size_to_go > 0) {
                        printf("%s: size_to_go = %zu, software error!\n",
                               __func__, size_to_go);
                        error = EINVAL;
                        goto bailout;
                }

                *data_ptrs[0] = (uint8_t *)io_req->kern_segptr;
                *seg_cnt_ptr = io_req->num_kern_segs;

                /*
                 * We only need to copy data here if the user is writing.
                 */
                if (dirs[0] == CAM_DIR_OUT)
                        error = passcopysglist(periph, io_req, dirs[0]);
                break;
        }
        case CAM_DATA_SG_PADDR: {
                size_t sg_length;

                /*
                 * We shouldn't see this, but check just in case.
                 */
                if (numbufs != 1) {
                        printf("%s: cannot currently handle more than one "
                               "S/G list per CCB\n", __func__);
                        error = EINVAL;
                        goto bailout;
                }

                /*
                 * We have to have at least one segment.
                 */
                if (num_segs == 0) {
                        xpt_print(periph->path, "%s: CAM_DATA_SG_PADDR flag "
                                  "set, but sglist_cnt=0!\n", __func__);
                        error = EINVAL;
                        goto bailout;
                }

                /*
                 * Make sure the user specified the total length and didn't
                 * just leave it to us to decode the S/G list.
                 */
                if (lengths[0] == 0) {
                        xpt_print(periph->path, "%s: no dxfer_len specified, "
                                  "but CAM_DATA_SG flag is set!\n", __func__);
                        error = EINVAL;
                        goto bailout;
                }

                /* Figure out the size of the S/G list */
                sg_length = num_segs * sizeof(bus_dma_segment_t);
                io_req->num_user_segs = num_segs;
                io_req->num_kern_segs = io_req->num_user_segs;

                /* Save the user's S/G list pointer for later restoration */
                io_req->user_bufs[0] = *data_ptrs[0];

                if (num_segs > PASS_MAX_SEGS) {
                        io_req->user_segptr = malloc(sizeof(bus_dma_segment_t) *
                            num_segs, M_SCSIPASS, M_WAITOK | M_ZERO);
                        io_req->flags |= PASS_IO_USER_SEG_MALLOC;
                } else
                        io_req->user_segptr = io_req->user_segs;

                io_req->kern_segptr = io_req->user_segptr;

                error = copyin(*data_ptrs[0], io_req->user_segptr, sg_length);
                if (error != 0) {
                        xpt_print(periph->path, "%s: copy of user S/G list "
                                  "from %p to %p failed with error %d\n",
                                  __func__, *data_ptrs[0], io_req->user_segptr,
                                  error);
                        goto bailout;
                }
                break;
        }
        default:
        case CAM_DATA_BIO:
                /*
                 * A user shouldn't be attaching a bio to the CCB.  It
                 * isn't a user-accessible structure.
                 */
                error = EINVAL;
                break;
        }

bailout:
        if (error != 0)
                passiocleanup(softc, io_req);

        return (error);
}

static int
passmemdone(struct cam_periph *periph, struct pass_io_req *io_req)
{
        struct pass_softc *softc;
        union ccb *ccb;
        int error;
        int i;

        error = 0;
        softc = (struct pass_softc *)periph->softc;
        ccb = &io_req->ccb;

        switch (io_req->data_flags) {
        case CAM_DATA_VADDR:
                /*
                 * Copy back to the user buffer if this was a read.
                 */
                for (i = 0; i < io_req->num_bufs; i++) {
                        if (io_req->dirs[i] != CAM_DIR_IN)
                                continue;

                        error = copyout(io_req->kern_bufs[i],
                            io_req->user_bufs[i], io_req->lengths[i]);
                        if (error != 0) {
                                xpt_print(periph->path, "Unable to copy %u "
                                          "bytes from %p to user address %p\n",
                                          io_req->lengths[i],
                                          io_req->kern_bufs[i],
                                          io_req->user_bufs[i]);
                                goto bailout;
                        }

                }
                break;
        case CAM_DATA_PADDR:
                /* Do nothing.  The pointer is a physical address already */
                break;
        case CAM_DATA_SG:
                /*
                 * Copy back to the user buffer if this was a read.
                 * Restore the user's S/G list buffer pointer.
                 */
                if (io_req->dirs[0] == CAM_DIR_IN)
                        error = passcopysglist(periph, io_req, io_req->dirs[0]);
                break;
        case CAM_DATA_SG_PADDR:
                /*
                 * Restore the user's S/G list buffer pointer.  No need to
                 * copy.
                 */
                break;
        default:
        case CAM_DATA_BIO:
                error = EINVAL;
                break;
        }

bailout:
        /*
         * Reset the user's pointers to their original values and free
         * allocated memory.
         */
        passiocleanup(softc, io_req);

        return (error);
}

static int
passioctl(struct cdev *dev, u_long cmd, caddr_t addr, int flag, struct thread *td)
{
        int error;

        if ((error = passdoioctl(dev, cmd, addr, flag, td)) == ENOTTY) {
                error = cam_compat_ioctl(dev, cmd, addr, flag, td, passdoioctl);
        }
        return (error);
}

static int
passdoioctl(struct cdev *dev, u_long cmd, caddr_t addr, int flag, struct thread *td)
{
        struct  cam_periph *periph;
        struct  pass_softc *softc;
        int     error;
        uint32_t priority;

        periph = (struct cam_periph *)dev->si_drv1;
        cam_periph_lock(periph);
        softc = (struct pass_softc *)periph->softc;

        error = 0;

        switch (cmd) {

        case CAMIOCOMMAND:
        {
                union ccb *inccb;
                union ccb *ccb;
                int ccb_malloced;

                inccb = (union ccb *)addr;

                /*
                 * Some CCB types, like scan bus and scan lun can only go
                 * through the transport layer device.
                 */
                if (inccb->ccb_h.func_code & XPT_FC_XPT_ONLY) {
                        xpt_print(periph->path, "CCB function code %#x is "
                            "restricted to the XPT device\n",
                            inccb->ccb_h.func_code);
                        error = ENODEV;
                        break;
                }

                /* Compatibility for RL/priority-unaware code. */
                priority = inccb->ccb_h.pinfo.priority;
                if (priority <= CAM_PRIORITY_OOB)
                    priority += CAM_PRIORITY_OOB + 1;

                /*
                 * Non-immediate CCBs need a CCB from the per-device pool
                 * of CCBs, which is scheduled by the transport layer.
                 * Immediate CCBs and user-supplied CCBs should just be
                 * malloced.
                 */
                if ((inccb->ccb_h.func_code & XPT_FC_QUEUED)
                 && ((inccb->ccb_h.func_code & XPT_FC_USER_CCB) == 0)) {
                        ccb = cam_periph_getccb(periph, priority);
                        ccb_malloced = 0;
                } else {
                        ccb = xpt_alloc_ccb_nowait();

                        if (ccb != NULL)
                                xpt_setup_ccb(&ccb->ccb_h, periph->path,
                                              priority);
                        ccb_malloced = 1;
                }

                if (ccb == NULL) {
                        xpt_print(periph->path, "unable to allocate CCB\n");
                        error = ENOMEM;
                        break;
                }

                error = passsendccb(periph, ccb, inccb);

                if (ccb_malloced)
                        xpt_free_ccb(ccb);
                else
                        xpt_release_ccb(ccb);

                break;
        }
        case CAMIOQUEUE:
        {
                struct pass_io_req *io_req;
                union ccb **user_ccb, *ccb;
                xpt_opcode fc;

                if ((softc->flags & PASS_FLAG_ZONE_VALID) == 0) {
                        error = passcreatezone(periph);
                        if (error != 0)
                                goto bailout;
                }

                /*
                 * We're going to do a blocking allocation for this I/O
                 * request, so we have to drop the lock.
                 */
                cam_periph_unlock(periph);

                io_req = uma_zalloc(softc->pass_zone, M_WAITOK | M_ZERO);
                ccb = &io_req->ccb;
                user_ccb = (union ccb **)addr;

                /*
                 * Unlike the CAMIOCOMMAND ioctl above, we only have a
                 * pointer to the user's CCB, so we have to copy the whole
                 * thing in to a buffer we have allocated (above) instead
                 * of allowing the ioctl code to malloc a buffer and copy
                 * it in.
                 *
                 * This is an advantage for this asynchronous interface,
                 * since we don't want the memory to get freed while the
                 * CCB is outstanding.
                 */
#if 0
                xpt_print(periph->path, "Copying user CCB %p to "
                          "kernel address %p\n", *user_ccb, ccb);
#endif
                error = copyin(*user_ccb, ccb, sizeof(*ccb));
                if (error != 0) {
                        xpt_print(periph->path, "Copy of user CCB %p to "
                                  "kernel address %p failed with error %d\n",
                                  *user_ccb, ccb, error);
                        uma_zfree(softc->pass_zone, io_req);
                        cam_periph_lock(periph);
                        break;
                }

                if (ccb->ccb_h.flags & CAM_CDB_POINTER) {
                        if (ccb->csio.cdb_len > IOCDBLEN) {
                                error = EINVAL;
                                break;
                        }
                        error = copyin(ccb->csio.cdb_io.cdb_ptr,
                            ccb->csio.cdb_io.cdb_bytes, ccb->csio.cdb_len);
                        if (error)
                                break;
                        ccb->ccb_h.flags &= ~CAM_CDB_POINTER;
                }

                /*
                 * Some CCB types, like scan bus and scan lun can only go
                 * through the transport layer device.
                 */
                if (ccb->ccb_h.func_code & XPT_FC_XPT_ONLY) {
                        xpt_print(periph->path, "CCB function code %#x is "
                            "restricted to the XPT device\n",
                            ccb->ccb_h.func_code);
                        uma_zfree(softc->pass_zone, io_req);
                        cam_periph_lock(periph);
                        error = ENODEV;
                        break;
                }

                /*
                 * Save the user's CCB pointer as well as his linked list
                 * pointers and peripheral private area so that we can
                 * restore these later.
                 */
                io_req->user_ccb_ptr = *user_ccb;
                io_req->user_periph_links = ccb->ccb_h.periph_links;
                io_req->user_periph_priv = ccb->ccb_h.periph_priv;

                /*
                 * Now that we've saved the user's values, we can set our
                 * own peripheral private entry.
                 */
                ccb->ccb_h.ccb_ioreq = io_req;

                /* Compatibility for RL/priority-unaware code. */
                priority = ccb->ccb_h.pinfo.priority;
                if (priority <= CAM_PRIORITY_OOB)
                    priority += CAM_PRIORITY_OOB + 1;

                /*
                 * Setup fields in the CCB like the path and the priority.
                 * The path in particular cannot be done in userland, since
                 * it is a pointer to a kernel data structure.
                 */
                xpt_setup_ccb_flags(&ccb->ccb_h, periph->path, priority,
                                    ccb->ccb_h.flags);

                /*
                 * Setup our done routine.  There is no way for the user to
                 * have a valid pointer here.
                 */
                ccb->ccb_h.cbfcnp = passdone;

                fc = ccb->ccb_h.func_code;
                /*
                 * If this function code has memory that can be mapped in
                 * or out, we need to call passmemsetup().
                 */
                if ((fc == XPT_SCSI_IO) || (fc == XPT_ATA_IO)
                 || (fc == XPT_SMP_IO) || (fc == XPT_DEV_MATCH)
                 || (fc == XPT_DEV_ADVINFO)) {
                        error = passmemsetup(periph, io_req);
                        if (error != 0) {
                                uma_zfree(softc->pass_zone, io_req);
                                cam_periph_lock(periph);
                                break;
                        }
                } else
                        io_req->mapinfo.num_bufs_used = 0;

                cam_periph_lock(periph);

                /*
                 * Everything goes on the incoming queue initially.
                 */
                TAILQ_INSERT_TAIL(&softc->incoming_queue, io_req, links);

                /*
                 * If the CCB is queued, and is not a user CCB, then
                 * we need to allocate a slot for it.  Call xpt_schedule()
                 * so that our start routine will get called when a CCB is
                 * available.
                 */
                if ((fc & XPT_FC_QUEUED)
                 && ((fc & XPT_FC_USER_CCB) == 0)) {
                        xpt_schedule(periph, priority);
                        break;
                } 

                /*
                 * At this point, the CCB in question is either an
                 * immediate CCB (like XPT_DEV_ADVINFO) or it is a user CCB
                 * and therefore should be malloced, not allocated via a slot.
                 * Remove the CCB from the incoming queue and add it to the
                 * active queue.
                 */
                TAILQ_REMOVE(&softc->incoming_queue, io_req, links);
                TAILQ_INSERT_TAIL(&softc->active_queue, io_req, links);

                xpt_action(ccb);

                /*
                 * If this is not a queued CCB (i.e. it is an immediate CCB),
                 * then it is already done.  We need to put it on the done
                 * queue for the user to fetch.
                 */
                if ((fc & XPT_FC_QUEUED) == 0) {
                        TAILQ_REMOVE(&softc->active_queue, io_req, links);
                        TAILQ_INSERT_TAIL(&softc->done_queue, io_req, links);
                }
                break;
        }
        case CAMIOGET:
        {
                union ccb **user_ccb;
                struct pass_io_req *io_req;
                int old_error;

                user_ccb = (union ccb **)addr;
                old_error = 0;

                io_req = TAILQ_FIRST(&softc->done_queue);
                if (io_req == NULL) {
                        error = ENOENT;
                        break;
                }

                /*
                 * Remove the I/O from the done queue.
                 */
                TAILQ_REMOVE(&softc->done_queue, io_req, links);

                /*
                 * We have to drop the lock during the copyout because the
                 * copyout can result in VM faults that require sleeping.
                 */
                cam_periph_unlock(periph);

                /*
                 * Do any needed copies (e.g. for reads) and revert the
                 * pointers in the CCB back to the user's pointers.
                 */
                error = passmemdone(periph, io_req);

                old_error = error;

                io_req->ccb.ccb_h.periph_links = io_req->user_periph_links;
                io_req->ccb.ccb_h.periph_priv = io_req->user_periph_priv;

#if 0
                xpt_print(periph->path, "Copying to user CCB %p from "
                          "kernel address %p\n", *user_ccb, &io_req->ccb);
#endif

                error = copyout(&io_req->ccb, *user_ccb, sizeof(union ccb));
                if (error != 0) {
                        xpt_print(periph->path, "Copy to user CCB %p from "
                                  "kernel address %p failed with error %d\n",
                                  *user_ccb, &io_req->ccb, error);
                }

                /*
                 * Prefer the first error we got back, and make sure we
                 * don't overwrite bad status with good.
                 */
                if (old_error != 0)
                        error = old_error;

                cam_periph_lock(periph);

                /*
                 * At this point, if there was an error, we could potentially
                 * re-queue the I/O and try again.  But why?  The error
                 * would almost certainly happen again.  We might as well
                 * not leak memory.
                 */
                uma_zfree(softc->pass_zone, io_req);
                break;
        }
        default:
                error = cam_periph_ioctl(periph, cmd, addr, passerror);
                break;
        }

bailout:
        cam_periph_unlock(periph);

        return(error);
}

static int
passpoll(struct cdev *dev, int poll_events, struct thread *td)
{
        struct cam_periph *periph;
        struct pass_softc *softc;
        int revents;

        periph = (struct cam_periph *)dev->si_drv1;
        softc = (struct pass_softc *)periph->softc;

        revents = poll_events & (POLLOUT | POLLWRNORM);
        if ((poll_events & (POLLIN | POLLRDNORM)) != 0) {
                cam_periph_lock(periph);

                if (!TAILQ_EMPTY(&softc->done_queue)) {
                        revents |= poll_events & (POLLIN | POLLRDNORM);
                }
                cam_periph_unlock(periph);
                if (revents == 0)
                        selrecord(td, &softc->read_select);
        }

        return (revents);
}

static int
passkqfilter(struct cdev *dev, struct knote *kn)
{
        struct cam_periph *periph;
        struct pass_softc *softc;

        periph = (struct cam_periph *)dev->si_drv1;
        softc = (struct pass_softc *)periph->softc;

        kn->kn_hook = (caddr_t)periph;
        kn->kn_fop = &passread_filtops;
        knlist_add(&softc->read_select.si_note, kn, 0);

        return (0);
}

static void
passreadfiltdetach(struct knote *kn)
{
        struct cam_periph *periph;
        struct pass_softc *softc;

        periph = (struct cam_periph *)kn->kn_hook;
        softc = (struct pass_softc *)periph->softc;

        knlist_remove(&softc->read_select.si_note, kn, 0);
}

static int
passreadfilt(struct knote *kn, long hint)
{
        struct cam_periph *periph;
        struct pass_softc *softc;
        int retval;

        periph = (struct cam_periph *)kn->kn_hook;
        softc = (struct pass_softc *)periph->softc;

        cam_periph_assert(periph, MA_OWNED);

        if (TAILQ_EMPTY(&softc->done_queue))
                retval = 0;
        else
                retval = 1;

        return (retval);
}

/*
 * Generally, "ccb" should be the CCB supplied by the kernel.  "inccb"
 * should be the CCB that is copied in from the user.
 */
static int
passsendccb(struct cam_periph *periph, union ccb *ccb, union ccb *inccb)
{
        struct pass_softc *softc;
        struct cam_periph_map_info mapinfo;
        uint8_t *cmd;
        xpt_opcode fc;
        int error;

        softc = (struct pass_softc *)periph->softc;

        /*
         * There are some fields in the CCB header that need to be
         * preserved, the rest we get from the user.
         */
        xpt_merge_ccb(ccb, inccb);

        if (ccb->ccb_h.flags & CAM_CDB_POINTER) {
                cmd = __builtin_alloca(ccb->csio.cdb_len);
                error = copyin(ccb->csio.cdb_io.cdb_ptr, cmd, ccb->csio.cdb_len);
                if (error)
                        return (error);
                ccb->csio.cdb_io.cdb_ptr = cmd;
        }

        /*
         */
        ccb->ccb_h.cbfcnp = passdone;

        /*
         * Let cam_periph_mapmem do a sanity check on the data pointer format.
         * Even if no data transfer is needed, it's a cheap check and it
         * simplifies the code.
         */
        fc = ccb->ccb_h.func_code;
        if ((fc == XPT_SCSI_IO) || (fc == XPT_ATA_IO) || (fc == XPT_SMP_IO)
         || (fc == XPT_DEV_MATCH) || (fc == XPT_DEV_ADVINFO)) {
                bzero(&mapinfo, sizeof(mapinfo));

                /*
                 * cam_periph_mapmem calls into proc and vm functions that can
                 * sleep as well as trigger I/O, so we can't hold the lock.
                 * Dropping it here is reasonably safe.
                 */
                cam_periph_unlock(periph);
                error = cam_periph_mapmem(ccb, &mapinfo, softc->maxio);
                cam_periph_lock(periph);

                /*
                 * cam_periph_mapmem returned an error, we can't continue.
                 * Return the error to the user.
                 */
                if (error)
                        return(error);
        } else
                /* Ensure that the unmap call later on is a no-op. */
                mapinfo.num_bufs_used = 0;

        /*
         * If the user wants us to perform any error recovery, then honor
         * that request.  Otherwise, it's up to the user to perform any
         * error recovery.
         */
        cam_periph_runccb(ccb, passerror, /* cam_flags */ CAM_RETRY_SELTO,
            /* sense_flags */ ((ccb->ccb_h.flags & CAM_PASS_ERR_RECOVER) ?
             SF_RETRY_UA : SF_NO_RECOVERY) | SF_NO_PRINT,
            softc->device_stats);

        cam_periph_unmapmem(ccb, &mapinfo);

        ccb->ccb_h.cbfcnp = NULL;
        ccb->ccb_h.periph_priv = inccb->ccb_h.periph_priv;
        bcopy(ccb, inccb, sizeof(union ccb));

        return(0);
}

static int
passerror(union ccb *ccb, u_int32_t cam_flags, u_int32_t sense_flags)
{
        struct cam_periph *periph;
        struct pass_softc *softc;

        periph = xpt_path_periph(ccb->ccb_h.path);
        softc = (struct pass_softc *)periph->softc;
        
        return(cam_periph_error(ccb, cam_flags, sense_flags, 
                                 &softc->saved_ccb));
}