kern_conf.c

Go to the documentation of this file.

/*-
 * Copyright (c) 1999-2002 Poul-Henning Kamp
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

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

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/bio.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/module.h>
#include <sys/malloc.h>
#include <sys/conf.h>
#include <sys/vnode.h>
#include <sys/queue.h>
#include <sys/poll.h>
#include <sys/sx.h>
#include <sys/ctype.h>
#include <sys/ucred.h>
#include <sys/taskqueue.h>
#include <machine/stdarg.h>

#include <fs/devfs/devfs_int.h>
#include <vm/vm.h>

static MALLOC_DEFINE(M_DEVT, "cdev", "cdev storage");

struct mtx devmtx;
static void destroy_devl(struct cdev *dev);
static int destroy_dev_sched_cbl(struct cdev *dev,
    void (*cb)(void *), void *arg);
static int make_dev_credv(int flags, struct cdev **dres, struct cdevsw *devsw,
    int unit, struct ucred *cr, uid_t uid, gid_t gid, int mode, const char *fmt,
    va_list ap);

static struct cdev_priv_list cdevp_free_list =
    TAILQ_HEAD_INITIALIZER(cdevp_free_list);
static SLIST_HEAD(free_cdevsw, cdevsw) cdevsw_gt_post_list =
    SLIST_HEAD_INITIALIZER(cdevsw_gt_post_list);

void
dev_lock(void)
{

        mtx_lock(&devmtx);
}

/*
 * Free all the memory collected while the cdev mutex was
 * locked. Since devmtx is after the system map mutex, free() cannot
 * be called immediately and is postponed until cdev mutex can be
 * dropped.
 */
static void
dev_unlock_and_free(void)
{
        struct cdev_priv_list cdp_free;
        struct free_cdevsw csw_free;
        struct cdev_priv *cdp;
        struct cdevsw *csw;

        mtx_assert(&devmtx, MA_OWNED);

        /*
         * Make the local copy of the list heads while the dev_mtx is
         * held. Free it later.
         */
        TAILQ_INIT(&cdp_free);
        TAILQ_CONCAT(&cdp_free, &cdevp_free_list, cdp_list);
        csw_free = cdevsw_gt_post_list;
        SLIST_INIT(&cdevsw_gt_post_list);

        mtx_unlock(&devmtx);

        while ((cdp = TAILQ_FIRST(&cdp_free)) != NULL) {
                TAILQ_REMOVE(&cdp_free, cdp, cdp_list);
                devfs_free(&cdp->cdp_c);
        }
        while ((csw = SLIST_FIRST(&csw_free)) != NULL) {
                SLIST_REMOVE_HEAD(&csw_free, d_postfree_list);
                free(csw, M_DEVT);
        }
}

static void
dev_free_devlocked(struct cdev *cdev)
{
        struct cdev_priv *cdp;

        mtx_assert(&devmtx, MA_OWNED);
        cdp = cdev2priv(cdev);
        KASSERT((cdp->cdp_flags & CDP_UNREF_DTR) == 0,
            ("destroy_dev() was not called after delist_dev(%p)", cdev));
        TAILQ_INSERT_HEAD(&cdevp_free_list, cdp, cdp_list);
}

static void
cdevsw_free_devlocked(struct cdevsw *csw)
{

        mtx_assert(&devmtx, MA_OWNED);
        SLIST_INSERT_HEAD(&cdevsw_gt_post_list, csw, d_postfree_list);
}

void
dev_unlock(void)
{

        mtx_unlock(&devmtx);
}

void
dev_ref(struct cdev *dev)
{

        mtx_assert(&devmtx, MA_NOTOWNED);
        mtx_lock(&devmtx);
        dev->si_refcount++;
        mtx_unlock(&devmtx);
}

void
dev_refl(struct cdev *dev)
{

        mtx_assert(&devmtx, MA_OWNED);
        dev->si_refcount++;
}

void
dev_rel(struct cdev *dev)
{
        int flag = 0;

        mtx_assert(&devmtx, MA_NOTOWNED);
        dev_lock();
        dev->si_refcount--;
        KASSERT(dev->si_refcount >= 0,
            ("dev_rel(%s) gave negative count", devtoname(dev)));
#if 0
        if (dev->si_usecount == 0 &&
            (dev->si_flags & SI_CHEAPCLONE) && (dev->si_flags & SI_NAMED))
                ;
        else 
#endif
        if (dev->si_devsw == NULL && dev->si_refcount == 0) {
                LIST_REMOVE(dev, si_list);
                flag = 1;
        }
        dev_unlock();
        if (flag)
                devfs_free(dev);
}

struct cdevsw *
dev_refthread(struct cdev *dev, int *ref)
{
        struct cdevsw *csw;
        struct cdev_priv *cdp;

        mtx_assert(&devmtx, MA_NOTOWNED);
        if ((dev->si_flags & SI_ETERNAL) != 0) {
                *ref = 0;
                return (dev->si_devsw);
        }
        dev_lock();
        csw = dev->si_devsw;
        if (csw != NULL) {
                cdp = cdev2priv(dev);
                if ((cdp->cdp_flags & CDP_SCHED_DTR) == 0)
                        dev->si_threadcount++;
                else
                        csw = NULL;
        }
        dev_unlock();
        *ref = 1;
        return (csw);
}

struct cdevsw *
devvn_refthread(struct vnode *vp, struct cdev **devp, int *ref)
{
        struct cdevsw *csw;
        struct cdev_priv *cdp;
        struct cdev *dev;

        mtx_assert(&devmtx, MA_NOTOWNED);
        if ((vp->v_vflag & VV_ETERNALDEV) != 0) {
                dev = vp->v_rdev;
                if (dev == NULL)
                        return (NULL);
                KASSERT((dev->si_flags & SI_ETERNAL) != 0,
                    ("Not eternal cdev"));
                *ref = 0;
                csw = dev->si_devsw;
                KASSERT(csw != NULL, ("Eternal cdev is destroyed"));
                *devp = dev;
                return (csw);
        }

        csw = NULL;
        dev_lock();
        dev = vp->v_rdev;
        if (dev == NULL) {
                dev_unlock();
                return (NULL);
        }
        cdp = cdev2priv(dev);
        if ((cdp->cdp_flags & CDP_SCHED_DTR) == 0) {
                csw = dev->si_devsw;
                if (csw != NULL)
                        dev->si_threadcount++;
        }
        dev_unlock();
        if (csw != NULL) {
                *devp = dev;
                *ref = 1;
        }
        return (csw);
}

void    
dev_relthread(struct cdev *dev, int ref)
{

        mtx_assert(&devmtx, MA_NOTOWNED);
        if (!ref)
                return;
        dev_lock();
        KASSERT(dev->si_threadcount > 0,
            ("%s threadcount is wrong", dev->si_name));
        dev->si_threadcount--;
        dev_unlock();
}

int
nullop(void)
{

        return (0);
}

int
eopnotsupp(void)
{

        return (EOPNOTSUPP);
}

static int
enxio(void)
{
        return (ENXIO);
}

static int
enodev(void)
{
        return (ENODEV);
}

/* Define a dead_cdevsw for use when devices leave unexpectedly. */

#define dead_open       (d_open_t *)enxio
#define dead_close      (d_close_t *)enxio
#define dead_read       (d_read_t *)enxio
#define dead_write      (d_write_t *)enxio
#define dead_ioctl      (d_ioctl_t *)enxio
#define dead_poll       (d_poll_t *)enodev
#define dead_mmap       (d_mmap_t *)enodev

static void
dead_strategy(struct bio *bp)
{

        biofinish(bp, NULL, ENXIO);
}

#define dead_dump       (dumper_t *)enxio
#define dead_kqfilter   (d_kqfilter_t *)enxio
#define dead_mmap_single (d_mmap_single_t *)enodev

static struct cdevsw dead_cdevsw = {
        .d_version =    D_VERSION,
        .d_open =       dead_open,
        .d_close =      dead_close,
        .d_read =       dead_read,
        .d_write =      dead_write,
        .d_ioctl =      dead_ioctl,
        .d_poll =       dead_poll,
        .d_mmap =       dead_mmap,
        .d_strategy =   dead_strategy,
        .d_name =       "dead",
        .d_dump =       dead_dump,
        .d_kqfilter =   dead_kqfilter,
        .d_mmap_single = dead_mmap_single
};

/* Default methods if driver does not specify method */

#define null_open       (d_open_t *)nullop
#define null_close      (d_close_t *)nullop
#define no_read         (d_read_t *)enodev
#define no_write        (d_write_t *)enodev
#define no_ioctl        (d_ioctl_t *)enodev
#define no_mmap         (d_mmap_t *)enodev
#define no_kqfilter     (d_kqfilter_t *)enodev
#define no_mmap_single  (d_mmap_single_t *)enodev

static void
no_strategy(struct bio *bp)
{

        biofinish(bp, NULL, ENODEV);
}

static int
no_poll(struct cdev *dev __unused, int events, struct thread *td __unused)
{

        return (poll_no_poll(events));
}

#define no_dump         (dumper_t *)enodev

static int
giant_open(struct cdev *dev, int oflags, int devtype, struct thread *td)
{
        struct cdevsw *dsw;
        int ref, retval;

        dsw = dev_refthread(dev, &ref);
        if (dsw == NULL)
                return (ENXIO);
        mtx_lock(&Giant);
        retval = dsw->d_gianttrick->d_open(dev, oflags, devtype, td);
        mtx_unlock(&Giant);
        dev_relthread(dev, ref);
        return (retval);
}

static int
giant_fdopen(struct cdev *dev, int oflags, struct thread *td, struct file *fp)
{
        struct cdevsw *dsw;
        int ref, retval;

        dsw = dev_refthread(dev, &ref);
        if (dsw == NULL)
                return (ENXIO);
        mtx_lock(&Giant);
        retval = dsw->d_gianttrick->d_fdopen(dev, oflags, td, fp);
        mtx_unlock(&Giant);
        dev_relthread(dev, ref);
        return (retval);
}

static int
giant_close(struct cdev *dev, int fflag, int devtype, struct thread *td)
{
        struct cdevsw *dsw;
        int ref, retval;

        dsw = dev_refthread(dev, &ref);
        if (dsw == NULL)
                return (ENXIO);
        mtx_lock(&Giant);
        retval = dsw->d_gianttrick->d_close(dev, fflag, devtype, td);
        mtx_unlock(&Giant);
        dev_relthread(dev, ref);
        return (retval);
}

static void
giant_strategy(struct bio *bp)
{
        struct cdevsw *dsw;
        struct cdev *dev;
        int ref;

        dev = bp->bio_dev;
        dsw = dev_refthread(dev, &ref);
        if (dsw == NULL) {
                biofinish(bp, NULL, ENXIO);
                return;
        }
        mtx_lock(&Giant);
        dsw->d_gianttrick->d_strategy(bp);
        mtx_unlock(&Giant);
        dev_relthread(dev, ref);
}

static int
giant_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int fflag, struct thread *td)
{
        struct cdevsw *dsw;
        int ref, retval;

        dsw = dev_refthread(dev, &ref);
        if (dsw == NULL)
                return (ENXIO);
        mtx_lock(&Giant);
        retval = dsw->d_gianttrick->d_ioctl(dev, cmd, data, fflag, td);
        mtx_unlock(&Giant);
        dev_relthread(dev, ref);
        return (retval);
}
  
static int
giant_read(struct cdev *dev, struct uio *uio, int ioflag)
{
        struct cdevsw *dsw;
        int ref, retval;

        dsw = dev_refthread(dev, &ref);
        if (dsw == NULL)
                return (ENXIO);
        mtx_lock(&Giant);
        retval = dsw->d_gianttrick->d_read(dev, uio, ioflag);
        mtx_unlock(&Giant);
        dev_relthread(dev, ref);
        return (retval);
}

static int
giant_write(struct cdev *dev, struct uio *uio, int ioflag)
{
        struct cdevsw *dsw;
        int ref, retval;

        dsw = dev_refthread(dev, &ref);
        if (dsw == NULL)
                return (ENXIO);
        mtx_lock(&Giant);
        retval = dsw->d_gianttrick->d_write(dev, uio, ioflag);
        mtx_unlock(&Giant);
        dev_relthread(dev, ref);
        return (retval);
}

static int
giant_poll(struct cdev *dev, int events, struct thread *td)
{
        struct cdevsw *dsw;
        int ref, retval;

        dsw = dev_refthread(dev, &ref);
        if (dsw == NULL)
                return (ENXIO);
        mtx_lock(&Giant);
        retval = dsw->d_gianttrick->d_poll(dev, events, td);
        mtx_unlock(&Giant);
        dev_relthread(dev, ref);
        return (retval);
}

static int
giant_kqfilter(struct cdev *dev, struct knote *kn)
{
        struct cdevsw *dsw;
        int ref, retval;

        dsw = dev_refthread(dev, &ref);
        if (dsw == NULL)
                return (ENXIO);
        mtx_lock(&Giant);
        retval = dsw->d_gianttrick->d_kqfilter(dev, kn);
        mtx_unlock(&Giant);
        dev_relthread(dev, ref);
        return (retval);
}

static int
giant_mmap(struct cdev *dev, vm_ooffset_t offset, vm_paddr_t *paddr, int nprot,
    vm_memattr_t *memattr)
{
        struct cdevsw *dsw;
        int ref, retval;

        dsw = dev_refthread(dev, &ref);
        if (dsw == NULL)
                return (ENXIO);
        mtx_lock(&Giant);
        retval = dsw->d_gianttrick->d_mmap(dev, offset, paddr, nprot,
            memattr);
        mtx_unlock(&Giant);
        dev_relthread(dev, ref);
        return (retval);
}

static int
giant_mmap_single(struct cdev *dev, vm_ooffset_t *offset, vm_size_t size,
    vm_object_t *object, int nprot)
{
        struct cdevsw *dsw;
        int ref, retval;

        dsw = dev_refthread(dev, &ref);
        if (dsw == NULL)
                return (ENXIO);
        mtx_lock(&Giant);
        retval = dsw->d_gianttrick->d_mmap_single(dev, offset, size, object,
            nprot);
        mtx_unlock(&Giant);
        dev_relthread(dev, ref);
        return (retval);
}

static void
notify(struct cdev *dev, const char *ev, int flags)
{
        static const char prefix[] = "cdev=";
        char *data;
        int namelen, mflags;

        if (cold)
                return;
        mflags = (flags & MAKEDEV_NOWAIT) ? M_NOWAIT : M_WAITOK;
        namelen = strlen(dev->si_name);
        data = malloc(namelen + sizeof(prefix), M_TEMP, mflags);
        if (data == NULL)
                return;
        memcpy(data, prefix, sizeof(prefix) - 1);
        memcpy(data + sizeof(prefix) - 1, dev->si_name, namelen + 1);
        devctl_notify_f("DEVFS", "CDEV", ev, data, mflags);
        free(data, M_TEMP);
}

static void
notify_create(struct cdev *dev, int flags)
{

        notify(dev, "CREATE", flags);
}

static void
notify_destroy(struct cdev *dev)
{

        notify(dev, "DESTROY", MAKEDEV_WAITOK);
}

static struct cdev *
newdev(struct cdevsw *csw, int unit, struct cdev *si)
{
        struct cdev *si2;

        mtx_assert(&devmtx, MA_OWNED);
        if (csw->d_flags & D_NEEDMINOR) {
                /* We may want to return an existing device */
                LIST_FOREACH(si2, &csw->d_devs, si_list) {
                        if (dev2unit(si2) == unit) {
                                dev_free_devlocked(si);
                                return (si2);
                        }
                }
        }
        si->si_drv0 = unit;
        si->si_devsw = csw;
        LIST_INSERT_HEAD(&csw->d_devs, si, si_list);
        return (si);
}

static void
fini_cdevsw(struct cdevsw *devsw)
{
        struct cdevsw *gt;

        if (devsw->d_gianttrick != NULL) {
                gt = devsw->d_gianttrick;
                memcpy(devsw, gt, sizeof *devsw);
                cdevsw_free_devlocked(gt);
                devsw->d_gianttrick = NULL;
        }
        devsw->d_flags &= ~D_INIT;
}

static int
prep_cdevsw(struct cdevsw *devsw, int flags)
{
        struct cdevsw *dsw2;

        mtx_assert(&devmtx, MA_OWNED);
        if (devsw->d_flags & D_INIT)
                return (0);
        if (devsw->d_flags & D_NEEDGIANT) {
                dev_unlock();
                dsw2 = malloc(sizeof *dsw2, M_DEVT,
                     (flags & MAKEDEV_NOWAIT) ? M_NOWAIT : M_WAITOK);
                dev_lock();
                if (dsw2 == NULL && !(devsw->d_flags & D_INIT))
                        return (ENOMEM);
        } else
                dsw2 = NULL;
        if (devsw->d_flags & D_INIT) {
                if (dsw2 != NULL)
                        cdevsw_free_devlocked(dsw2);
                return (0);
        }

        if (devsw->d_version != D_VERSION_03) {
                printf(
                    "WARNING: Device driver \"%s\" has wrong version %s\n",
                    devsw->d_name == NULL ? "???" : devsw->d_name,
                    "and is disabled.  Recompile KLD module.");
                devsw->d_open = dead_open;
                devsw->d_close = dead_close;
                devsw->d_read = dead_read;
                devsw->d_write = dead_write;
                devsw->d_ioctl = dead_ioctl;
                devsw->d_poll = dead_poll;
                devsw->d_mmap = dead_mmap;
                devsw->d_mmap_single = dead_mmap_single;
                devsw->d_strategy = dead_strategy;
                devsw->d_dump = dead_dump;
                devsw->d_kqfilter = dead_kqfilter;
        }
        
        if (devsw->d_flags & D_NEEDGIANT) {
                if (devsw->d_gianttrick == NULL) {
                        memcpy(dsw2, devsw, sizeof *dsw2);
                        devsw->d_gianttrick = dsw2;
                        dsw2 = NULL;
                }
        }

#define FIXUP(member, noop, giant)                              \
        do {                                                    \
                if (devsw->member == NULL) {                    \
                        devsw->member = noop;                   \
                } else if (devsw->d_flags & D_NEEDGIANT)        \
                        devsw->member = giant;                  \
                }                                               \
        while (0)

        FIXUP(d_open,           null_open,      giant_open);
        FIXUP(d_fdopen,         NULL,           giant_fdopen);
        FIXUP(d_close,          null_close,     giant_close);
        FIXUP(d_read,           no_read,        giant_read);
        FIXUP(d_write,          no_write,       giant_write);
        FIXUP(d_ioctl,          no_ioctl,       giant_ioctl);
        FIXUP(d_poll,           no_poll,        giant_poll);
        FIXUP(d_mmap,           no_mmap,        giant_mmap);
        FIXUP(d_strategy,       no_strategy,    giant_strategy);
        FIXUP(d_kqfilter,       no_kqfilter,    giant_kqfilter);
        FIXUP(d_mmap_single,    no_mmap_single, giant_mmap_single);

        if (devsw->d_dump == NULL)      devsw->d_dump = no_dump;

        LIST_INIT(&devsw->d_devs);

        devsw->d_flags |= D_INIT;

        if (dsw2 != NULL)
                cdevsw_free_devlocked(dsw2);
        return (0);
}

static int
prep_devname(struct cdev *dev, const char *fmt, va_list ap)
{
        int len;
        char *from, *q, *s, *to;

        mtx_assert(&devmtx, MA_OWNED);

        len = vsnrprintf(dev->__si_namebuf, sizeof(dev->__si_namebuf), 32,
            fmt, ap);
        if (len > sizeof(dev->__si_namebuf) - 1)
                return (ENAMETOOLONG);

        /* Strip leading slashes. */
        for (from = dev->__si_namebuf; *from == '/'; from++)
                ;

        for (to = dev->__si_namebuf; *from != '\0'; from++, to++) {
                /* Treat multiple sequential slashes as single. */
                while (from[0] == '/' && from[1] == '/')
                        from++;
                /* Trailing slash is considered invalid. */
                if (from[0] == '/' && from[1] == '\0')
                        return (EINVAL);
                *to = *from;
        }
        *to = '\0';

        if (dev->__si_namebuf[0] == '\0')
                return (EINVAL);

        /* Disallow "." and ".." components. */
        for (s = dev->__si_namebuf;;) {
                for (q = s; *q != '/' && *q != '\0'; q++)
                        ;
                if (q - s == 1 && s[0] == '.')
                        return (EINVAL);
                if (q - s == 2 && s[0] == '.' && s[1] == '.')
                        return (EINVAL);
                if (*q != '/')
                        break;
                s = q + 1;
        }

        if (devfs_dev_exists(dev->__si_namebuf) != 0)
                return (EEXIST);

        return (0);
}

static int
make_dev_credv(int flags, struct cdev **dres, struct cdevsw *devsw, int unit,
    struct ucred *cr, uid_t uid, gid_t gid, int mode, const char *fmt,
    va_list ap)
{
        struct cdev *dev, *dev_new;
        int res;

        KASSERT((flags & MAKEDEV_WAITOK) == 0 || (flags & MAKEDEV_NOWAIT) == 0,
            ("make_dev_credv: both WAITOK and NOWAIT specified"));
        dev_new = devfs_alloc(flags);
        if (dev_new == NULL)
                return (ENOMEM);
        dev_lock();
        res = prep_cdevsw(devsw, flags);
        if (res != 0) {
                dev_unlock();
                devfs_free(dev_new);
                return (res);
        }
        dev = newdev(devsw, unit, dev_new);
        if ((dev->si_flags & SI_NAMED) == 0) {
                res = prep_devname(dev, fmt, ap);
                if (res != 0) {
                        if ((flags & MAKEDEV_CHECKNAME) == 0) {
                                panic(
                        "make_dev_credv: bad si_name (error=%d, si_name=%s)",
                                    res, dev->si_name);
                        }
                        if (dev == dev_new) {
                                LIST_REMOVE(dev, si_list);
                                dev_unlock();
                                devfs_free(dev);
                        } else
                                dev_unlock();
                        return (res);
                }
        }
        if (flags & MAKEDEV_REF)
                dev_refl(dev);
        if (flags & MAKEDEV_ETERNAL)
                dev->si_flags |= SI_ETERNAL;
        if (dev->si_flags & SI_CHEAPCLONE &&
            dev->si_flags & SI_NAMED) {
                /*
                 * This is allowed as it removes races and generally
                 * simplifies cloning devices.
                 * XXX: still ??
                 */
                dev_unlock_and_free();
                *dres = dev;
                return (0);
        }
        KASSERT(!(dev->si_flags & SI_NAMED),
            ("make_dev() by driver %s on pre-existing device (min=%x, name=%s)",
            devsw->d_name, dev2unit(dev), devtoname(dev)));
        dev->si_flags |= SI_NAMED;
        if (cr != NULL)
                dev->si_cred = crhold(cr);
        dev->si_uid = uid;
        dev->si_gid = gid;
        dev->si_mode = mode;

        devfs_create(dev);
        clean_unrhdrl(devfs_inos);
        dev_unlock_and_free();

        notify_create(dev, flags);

        *dres = dev;
        return (0);
}

struct cdev *
make_dev(struct cdevsw *devsw, int unit, uid_t uid, gid_t gid, int mode,
    const char *fmt, ...)
{
        struct cdev *dev;
        va_list ap;
        int res;

        va_start(ap, fmt);
        res = make_dev_credv(0, &dev, devsw, unit, NULL, uid, gid, mode, fmt,
            ap);
        va_end(ap);
        KASSERT(res == 0 && dev != NULL,
            ("make_dev: failed make_dev_credv (error=%d)", res));
        return (dev);
}

struct cdev *
make_dev_cred(struct cdevsw *devsw, int unit, struct ucred *cr, uid_t uid,
    gid_t gid, int mode, const char *fmt, ...)
{
        struct cdev *dev;
        va_list ap;
        int res;

        va_start(ap, fmt);
        res = make_dev_credv(0, &dev, devsw, unit, cr, uid, gid, mode, fmt, ap);
        va_end(ap);

        KASSERT(res == 0 && dev != NULL,
            ("make_dev_cred: failed make_dev_credv (error=%d)", res));
        return (dev);
}

struct cdev *
make_dev_credf(int flags, struct cdevsw *devsw, int unit, struct ucred *cr,
    uid_t uid, gid_t gid, int mode, const char *fmt, ...)
{
        struct cdev *dev;
        va_list ap;
        int res;

        va_start(ap, fmt);
        res = make_dev_credv(flags, &dev, devsw, unit, cr, uid, gid, mode,
            fmt, ap);
        va_end(ap);

        KASSERT(((flags & MAKEDEV_NOWAIT) != 0 && res == ENOMEM) ||
            ((flags & MAKEDEV_CHECKNAME) != 0 && res != ENOMEM) || res == 0,
            ("make_dev_credf: failed make_dev_credv (error=%d)", res));
        return (res == 0 ? dev : NULL);
}

int
make_dev_p(int flags, struct cdev **cdev, struct cdevsw *devsw,
    struct ucred *cr, uid_t uid, gid_t gid, int mode, const char *fmt, ...)
{
        va_list ap;
        int res;

        va_start(ap, fmt);
        res = make_dev_credv(flags, cdev, devsw, 0, cr, uid, gid, mode,
            fmt, ap);
        va_end(ap);

        KASSERT(((flags & MAKEDEV_NOWAIT) != 0 && res == ENOMEM) ||
            ((flags & MAKEDEV_CHECKNAME) != 0 && res != ENOMEM) || res == 0,
            ("make_dev_p: failed make_dev_credv (error=%d)", res));
        return (res);
}

static void
dev_dependsl(struct cdev *pdev, struct cdev *cdev)
{

        cdev->si_parent = pdev;
        cdev->si_flags |= SI_CHILD;
        LIST_INSERT_HEAD(&pdev->si_children, cdev, si_siblings);
}


void
dev_depends(struct cdev *pdev, struct cdev *cdev)
{

        dev_lock();
        dev_dependsl(pdev, cdev);
        dev_unlock();
}

static int
make_dev_alias_v(int flags, struct cdev **cdev, struct cdev *pdev,
    const char *fmt, va_list ap)
{
        struct cdev *dev;
        int error;

        KASSERT(pdev != NULL, ("make_dev_alias_v: pdev is NULL"));
        KASSERT((flags & MAKEDEV_WAITOK) == 0 || (flags & MAKEDEV_NOWAIT) == 0,
            ("make_dev_alias_v: both WAITOK and NOWAIT specified"));
        KASSERT((flags & ~(MAKEDEV_WAITOK | MAKEDEV_NOWAIT |
            MAKEDEV_CHECKNAME)) == 0,
            ("make_dev_alias_v: invalid flags specified (flags=%02x)", flags));

        dev = devfs_alloc(flags);
        if (dev == NULL)
                return (ENOMEM);
        dev_lock();
        dev->si_flags |= SI_ALIAS;
        error = prep_devname(dev, fmt, ap);
        if (error != 0) {
                if ((flags & MAKEDEV_CHECKNAME) == 0) {
                        panic("make_dev_alias_v: bad si_name "
                            "(error=%d, si_name=%s)", error, dev->si_name);
                }
                dev_unlock();
                devfs_free(dev);
                return (error);
        }
        dev->si_flags |= SI_NAMED;
        devfs_create(dev);
        dev_dependsl(pdev, dev);
        clean_unrhdrl(devfs_inos);
        dev_unlock();

        notify_create(dev, flags);
        *cdev = dev;

        return (0);
}

struct cdev *
make_dev_alias(struct cdev *pdev, const char *fmt, ...)
{
        struct cdev *dev;
        va_list ap;
        int res;

        va_start(ap, fmt);
        res = make_dev_alias_v(MAKEDEV_WAITOK, &dev, pdev, fmt, ap);
        va_end(ap);

        KASSERT(res == 0 && dev != NULL,
            ("make_dev_alias: failed make_dev_alias_v (error=%d)", res));
        return (dev);
}

int
make_dev_alias_p(int flags, struct cdev **cdev, struct cdev *pdev,
    const char *fmt, ...)
{
        va_list ap;
        int res;

        va_start(ap, fmt);
        res = make_dev_alias_v(flags, cdev, pdev, fmt, ap);
        va_end(ap);
        return (res);
}

int
make_dev_physpath_alias(int flags, struct cdev **cdev, struct cdev *pdev, 
    struct cdev *old_alias, const char *physpath)
{
        char *devfspath;
        int physpath_len;
        int max_parentpath_len;
        int parentpath_len;
        int devfspathbuf_len;
        int mflags;
        int ret;

        *cdev = NULL;
        devfspath = NULL;
        physpath_len = strlen(physpath);
        ret = EINVAL;
        if (physpath_len == 0)
                goto out;

        if (strncmp("id1,", physpath, 4) == 0) {
                physpath += 4;
                physpath_len -= 4;
                if (physpath_len == 0)
                        goto out;
        }

        max_parentpath_len = SPECNAMELEN - physpath_len - /*/*/1;
        parentpath_len = strlen(pdev->si_name);
        if (max_parentpath_len < parentpath_len) {
                if (bootverbose)
                        printf("WARNING: Unable to alias %s "
                            "to %s/%s - path too long\n",
                            pdev->si_name, physpath, pdev->si_name);
                ret = ENAMETOOLONG;
                goto out;
        }

        mflags = (flags & MAKEDEV_NOWAIT) ? M_NOWAIT : M_WAITOK;
        devfspathbuf_len = physpath_len + /*/*/1 + parentpath_len + /*NUL*/1;
        devfspath = malloc(devfspathbuf_len, M_DEVBUF, mflags);
        if (devfspath == NULL) {
                ret = ENOMEM;
                goto out;
        }

        sprintf(devfspath, "%s/%s", physpath, pdev->si_name);
        if (old_alias != NULL && strcmp(old_alias->si_name, devfspath) == 0) {
                /* Retain the existing alias. */
                *cdev = old_alias;
                old_alias = NULL;
                ret = 0;
        } else {
                ret = make_dev_alias_p(flags, cdev, pdev, "%s", devfspath);
        }
out:
        if (old_alias != NULL)  
                destroy_dev(old_alias);
        if (devfspath != NULL)
                free(devfspath, M_DEVBUF);
        return (ret);
}

static void
destroy_devl(struct cdev *dev)
{
        struct cdevsw *csw;
        struct cdev_privdata *p;
        struct cdev_priv *cdp;

        mtx_assert(&devmtx, MA_OWNED);
        KASSERT(dev->si_flags & SI_NAMED,
            ("WARNING: Driver mistake: destroy_dev on %d\n", dev2unit(dev)));
        KASSERT((dev->si_flags & SI_ETERNAL) == 0,
            ("WARNING: Driver mistake: destroy_dev on eternal %d\n",
             dev2unit(dev)));

        cdp = cdev2priv(dev);
        if ((cdp->cdp_flags & CDP_UNREF_DTR) == 0) {
                /*
                 * Avoid race with dev_rel(), e.g. from the populate
                 * loop.  If CDP_UNREF_DTR flag is set, the reference
                 * to be dropped at the end of destroy_devl() was
                 * already taken by delist_dev_locked().
                 */
                dev_refl(dev);

                devfs_destroy(dev);
        }

        /* Remove name marking */
        dev->si_flags &= ~SI_NAMED;

        /* If we are a child, remove us from the parents list */
        if (dev->si_flags & SI_CHILD) {
                LIST_REMOVE(dev, si_siblings);
                dev->si_flags &= ~SI_CHILD;
        }

        /* Kill our children */
        while (!LIST_EMPTY(&dev->si_children))
                destroy_devl(LIST_FIRST(&dev->si_children));

        /* Remove from clone list */
        if (dev->si_flags & SI_CLONELIST) {
                LIST_REMOVE(dev, si_clone);
                dev->si_flags &= ~SI_CLONELIST;
        }

        csw = dev->si_devsw;
        dev->si_devsw = NULL;   /* already NULL for SI_ALIAS */
        while (csw != NULL && csw->d_purge != NULL && dev->si_threadcount) {
                csw->d_purge(dev);
                msleep(csw, &devmtx, PRIBIO, "devprg", hz/10);
                if (dev->si_threadcount)
                        printf("Still %lu threads in %s\n",
                            dev->si_threadcount, devtoname(dev));
        }
        while (dev->si_threadcount != 0) {
                /* Use unique dummy wait ident */
                msleep(&csw, &devmtx, PRIBIO, "devdrn", hz / 10);
        }

        dev_unlock();
        if ((cdp->cdp_flags & CDP_UNREF_DTR) == 0) {
                /* avoid out of order notify events */
                notify_destroy(dev);
        }
        mtx_lock(&cdevpriv_mtx);
        while ((p = LIST_FIRST(&cdp->cdp_fdpriv)) != NULL) {
                devfs_destroy_cdevpriv(p);
                mtx_lock(&cdevpriv_mtx);
        }
        mtx_unlock(&cdevpriv_mtx);
        dev_lock();

        dev->si_drv1 = 0;
        dev->si_drv2 = 0;
        bzero(&dev->__si_u, sizeof(dev->__si_u));

        if (!(dev->si_flags & SI_ALIAS)) {
                /* Remove from cdevsw list */
                LIST_REMOVE(dev, si_list);

                /* If cdevsw has no more struct cdev *'s, clean it */
                if (LIST_EMPTY(&csw->d_devs)) {
                        fini_cdevsw(csw);
                        wakeup(&csw->d_devs);
                }
        }
        dev->si_flags &= ~SI_ALIAS;
        cdp->cdp_flags &= ~CDP_UNREF_DTR;
        dev->si_refcount--;

        if (dev->si_refcount > 0)
                LIST_INSERT_HEAD(&dead_cdevsw.d_devs, dev, si_list);
        else
                dev_free_devlocked(dev);
}

static void
delist_dev_locked(struct cdev *dev)
{
        struct cdev_priv *cdp;
        struct cdev *child;

        mtx_assert(&devmtx, MA_OWNED);
        cdp = cdev2priv(dev);
        if ((cdp->cdp_flags & CDP_UNREF_DTR) != 0)
                return;
        cdp->cdp_flags |= CDP_UNREF_DTR;
        dev_refl(dev);
        devfs_destroy(dev);
        LIST_FOREACH(child, &dev->si_children, si_siblings)
                delist_dev_locked(child);
        dev_unlock();   
        /* ensure the destroy event is queued in order */
        notify_destroy(dev);
        dev_lock();
}

/*
 * This function will delist a character device and its children from
 * the directory listing and create a destroy event without waiting
 * for all character device references to go away. At some later point
 * destroy_dev() must be called to complete the character device
 * destruction. After calling this function the character device name
 * can instantly be re-used.
 */
void
delist_dev(struct cdev *dev)
{

        WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "delist_dev");
        dev_lock();
        delist_dev_locked(dev);
        dev_unlock();
}

void
destroy_dev(struct cdev *dev)
{

        WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "destroy_dev");
        dev_lock();
        destroy_devl(dev);
        dev_unlock_and_free();
}

const char *
devtoname(struct cdev *dev)
{

        return (dev->si_name);
}

int
dev_stdclone(char *name, char **namep, const char *stem, int *unit)
{
        int u, i;

        i = strlen(stem);
        if (bcmp(stem, name, i) != 0)
                return (0);
        if (!isdigit(name[i]))
                return (0);
        u = 0;
        if (name[i] == '0' && isdigit(name[i+1]))
                return (0);
        while (isdigit(name[i])) {
                u *= 10;
                u += name[i++] - '0';
        }
        if (u > 0xffffff)
                return (0);
        *unit = u;
        if (namep)
                *namep = &name[i];
        if (name[i]) 
                return (2);
        return (1);
}

/*
 * Helper functions for cloning device drivers.
 *
 * The objective here is to make it unnecessary for the device drivers to
 * use rman or similar to manage their unit number space.  Due to the way
 * we do "on-demand" devices, using rman or other "private" methods 
 * will be very tricky to lock down properly once we lock down this file.
 *
 * Instead we give the drivers these routines which puts the struct cdev *'s
 * that are to be managed on their own list, and gives the driver the ability
 * to ask for the first free unit number or a given specified unit number.
 *
 * In addition these routines support paired devices (pty, nmdm and similar)
 * by respecting a number of "flag" bits in the minor number.
 *
 */

struct clonedevs {
        LIST_HEAD(,cdev)        head;
};

void
clone_setup(struct clonedevs **cdp)
{

        *cdp = malloc(sizeof **cdp, M_DEVBUF, M_WAITOK | M_ZERO);
        LIST_INIT(&(*cdp)->head);
}

int
clone_create(struct clonedevs **cdp, struct cdevsw *csw, int *up,
    struct cdev **dp, int extra)
{
        struct clonedevs *cd;
        struct cdev *dev, *ndev, *dl, *de;
        int unit, low, u;

        KASSERT(*cdp != NULL,
            ("clone_setup() not called in driver \"%s\"", csw->d_name));
        KASSERT(!(extra & CLONE_UNITMASK),
            ("Illegal extra bits (0x%x) in clone_create", extra));
        KASSERT(*up <= CLONE_UNITMASK,
            ("Too high unit (0x%x) in clone_create", *up));
        KASSERT(csw->d_flags & D_NEEDMINOR,
            ("clone_create() on cdevsw without minor numbers"));


        /*
         * Search the list for a lot of things in one go:
         *   A preexisting match is returned immediately.
         *   The lowest free unit number if we are passed -1, and the place
         *       in the list where we should insert that new element.
         *   The place to insert a specified unit number, if applicable
         *       the end of the list.
         */
        unit = *up;
        ndev = devfs_alloc(MAKEDEV_WAITOK);
        dev_lock();
        prep_cdevsw(csw, MAKEDEV_WAITOK);
        low = extra;
        de = dl = NULL;
        cd = *cdp;
        LIST_FOREACH(dev, &cd->head, si_clone) {
                KASSERT(dev->si_flags & SI_CLONELIST,
                    ("Dev %p(%s) should be on clonelist", dev, dev->si_name));
                u = dev2unit(dev);
                if (u == (unit | extra)) {
                        *dp = dev;
                        dev_unlock();
                        devfs_free(ndev);
                        return (0);
                }
                if (unit == -1 && u == low) {
                        low++;
                        de = dev;
                        continue;
                } else if (u < (unit | extra)) {
                        de = dev;
                        continue;
                } else if (u > (unit | extra)) {
                        dl = dev;
                        break;
                }
        }
        if (unit == -1)
                unit = low & CLONE_UNITMASK;
        dev = newdev(csw, unit | extra, ndev);
        if (dev->si_flags & SI_CLONELIST) {
                printf("dev %p (%s) is on clonelist\n", dev, dev->si_name);
                printf("unit=%d, low=%d, extra=0x%x\n", unit, low, extra);
                LIST_FOREACH(dev, &cd->head, si_clone) {
                        printf("\t%p %s\n", dev, dev->si_name);
                }
                panic("foo");
        }
        KASSERT(!(dev->si_flags & SI_CLONELIST),
            ("Dev %p(%s) should not be on clonelist", dev, dev->si_name));
        if (dl != NULL)
                LIST_INSERT_BEFORE(dl, dev, si_clone);
        else if (de != NULL)
                LIST_INSERT_AFTER(de, dev, si_clone);
        else
                LIST_INSERT_HEAD(&cd->head, dev, si_clone);
        dev->si_flags |= SI_CLONELIST;
        *up = unit;
        dev_unlock_and_free();
        return (1);
}

/*
 * Kill everything still on the list.  The driver should already have
 * disposed of any softc hung of the struct cdev *'s at this time.
 */
void
clone_cleanup(struct clonedevs **cdp)
{
        struct cdev *dev;
        struct cdev_priv *cp;
        struct clonedevs *cd;
        
        cd = *cdp;
        if (cd == NULL)
                return;
        dev_lock();
        while (!LIST_EMPTY(&cd->head)) {
                dev = LIST_FIRST(&cd->head);
                LIST_REMOVE(dev, si_clone);
                KASSERT(dev->si_flags & SI_CLONELIST,
                    ("Dev %p(%s) should be on clonelist", dev, dev->si_name));
                dev->si_flags &= ~SI_CLONELIST;
                cp = cdev2priv(dev);
                if (!(cp->cdp_flags & CDP_SCHED_DTR)) {
                        cp->cdp_flags |= CDP_SCHED_DTR;
                        KASSERT(dev->si_flags & SI_NAMED,
                                ("Driver has goofed in cloning underways udev %x unit %x", dev2udev(dev), dev2unit(dev)));
                        destroy_devl(dev);
                }
        }
        dev_unlock_and_free();
        free(cd, M_DEVBUF);
        *cdp = NULL;
}

static TAILQ_HEAD(, cdev_priv) dev_ddtr =
        TAILQ_HEAD_INITIALIZER(dev_ddtr);
static struct task dev_dtr_task;

static void
destroy_dev_tq(void *ctx, int pending)
{
        struct cdev_priv *cp;
        struct cdev *dev;
        void (*cb)(void *);
        void *cb_arg;

        dev_lock();
        while (!TAILQ_EMPTY(&dev_ddtr)) {
                cp = TAILQ_FIRST(&dev_ddtr);
                dev = &cp->cdp_c;
                KASSERT(cp->cdp_flags & CDP_SCHED_DTR,
                    ("cdev %p in dev_destroy_tq without CDP_SCHED_DTR", cp));
                TAILQ_REMOVE(&dev_ddtr, cp, cdp_dtr_list);
                cb = cp->cdp_dtr_cb;
                cb_arg = cp->cdp_dtr_cb_arg;
                destroy_devl(dev);
                dev_unlock_and_free();
                dev_rel(dev);
                if (cb != NULL)
                        cb(cb_arg);
                dev_lock();
        }
        dev_unlock();
}

/*
 * devmtx shall be locked on entry. devmtx will be unlocked after
 * function return.
 */
static int
destroy_dev_sched_cbl(struct cdev *dev, void (*cb)(void *), void *arg)
{
        struct cdev_priv *cp;

        mtx_assert(&devmtx, MA_OWNED);
        cp = cdev2priv(dev);
        if (cp->cdp_flags & CDP_SCHED_DTR) {
                dev_unlock();
                return (0);
        }
        dev_refl(dev);
        cp->cdp_flags |= CDP_SCHED_DTR;
        cp->cdp_dtr_cb = cb;
        cp->cdp_dtr_cb_arg = arg;
        TAILQ_INSERT_TAIL(&dev_ddtr, cp, cdp_dtr_list);
        dev_unlock();
        taskqueue_enqueue(taskqueue_swi_giant, &dev_dtr_task);
        return (1);
}

int
destroy_dev_sched_cb(struct cdev *dev, void (*cb)(void *), void *arg)
{

        dev_lock();
        return (destroy_dev_sched_cbl(dev, cb, arg));
}

int
destroy_dev_sched(struct cdev *dev)
{

        return (destroy_dev_sched_cb(dev, NULL, NULL));
}

void
destroy_dev_drain(struct cdevsw *csw)
{

        dev_lock();
        while (!LIST_EMPTY(&csw->d_devs)) {
                msleep(&csw->d_devs, &devmtx, PRIBIO, "devscd", hz/10);
        }
        dev_unlock();
}

void
drain_dev_clone_events(void)
{

        sx_xlock(&clone_drain_lock);
        sx_xunlock(&clone_drain_lock);
}

static void
devdtr_init(void *dummy __unused)
{

        TASK_INIT(&dev_dtr_task, 0, destroy_dev_tq, NULL);
}

SYSINIT(devdtr, SI_SUB_DEVFS, SI_ORDER_SECOND, devdtr_init, NULL);

#include "opt_ddb.h"
#ifdef DDB
#include <sys/kernel.h>

#include <ddb/ddb.h>

DB_SHOW_COMMAND(cdev, db_show_cdev)
{
        struct cdev_priv *cdp;
        struct cdev *dev;
        u_int flags;
        char buf[512];

        if (!have_addr) {
                TAILQ_FOREACH(cdp, &cdevp_list, cdp_list) {
                        dev = &cdp->cdp_c;
                        db_printf("%s %p\n", dev->si_name, dev);
                        if (db_pager_quit)
                                break;
                }
                return;
        }

        dev = (struct cdev *)addr;
        cdp = cdev2priv(dev);
        db_printf("dev %s ref %d use %ld thr %ld inuse %u fdpriv %p\n",
            dev->si_name, dev->si_refcount, dev->si_usecount,
            dev->si_threadcount, cdp->cdp_inuse, cdp->cdp_fdpriv.lh_first);
        db_printf("devsw %p si_drv0 %d si_drv1 %p si_drv2 %p\n",
            dev->si_devsw, dev->si_drv0, dev->si_drv1, dev->si_drv2);
        flags = dev->si_flags;
#define SI_FLAG(flag)   do {                                            \
        if (flags & (flag)) {                                           \
                if (buf[0] != '\0')                                     \
                        strlcat(buf, ", ", sizeof(buf));                \
                strlcat(buf, (#flag) + 3, sizeof(buf));                 \
                flags &= ~(flag);                                       \
        }                                                               \
} while (0)
        buf[0] = '\0';
        SI_FLAG(SI_ETERNAL);
        SI_FLAG(SI_ALIAS);
        SI_FLAG(SI_NAMED);
        SI_FLAG(SI_CHEAPCLONE);
        SI_FLAG(SI_CHILD);
        SI_FLAG(SI_DEVOPEN);
        SI_FLAG(SI_CONSOPEN);
        SI_FLAG(SI_DUMPDEV);
        SI_FLAG(SI_CANDELETE);
        SI_FLAG(SI_CLONELIST);
        db_printf("si_flags %s\n", buf);

        flags = cdp->cdp_flags;
#define CDP_FLAG(flag)  do {                                            \
        if (flags & (flag)) {                                           \
                if (buf[0] != '\0')                                     \
                        strlcat(buf, ", ", sizeof(buf));                \
                strlcat(buf, (#flag) + 4, sizeof(buf));                 \
                flags &= ~(flag);                                       \
        }                                                               \
} while (0)
        buf[0] = '\0';
        CDP_FLAG(CDP_ACTIVE);
        CDP_FLAG(CDP_SCHED_DTR);
        db_printf("cdp_flags %s\n", buf);
}
#endif