MFC r1.27:

[dragonfly.git] / sys / kern / kern_conf.c

/*-
 * Parts Copyright (c) 1995 Terrence R. Lambert
 * Copyright (c) 1995 Julian R. Elischer
 * 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by Terrence R. Lambert.
 * 4. The name Terrence R. Lambert may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY Julian R. Elischer ``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 TERRENCE R. LAMBERT 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.
 *
 * $FreeBSD: src/sys/kern/kern_conf.c,v 1.73.2.3 2003/03/10 02:18:25 imp Exp $
 * $DragonFly: src/sys/kern/kern_conf.c,v 1.23 2007/05/09 00:53:34 dillon Exp $
 */

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/module.h>
#include <sys/malloc.h>
#include <sys/conf.h>
#include <sys/vnode.h>
#include <sys/queue.h>
#include <sys/device.h>
#include <machine/stdarg.h>

#include <sys/sysref2.h>

static void cdev_terminate(struct cdev *dev);

MALLOC_DEFINE(M_DEVT, "cdev_t", "dev_t storage");

/*
 * SYSREF Integration - reference counting, allocation,
 * sysid and syslink integration.
 */
static struct sysref_class     cdev_sysref_class = {
        .name =         "cdev",
        .mtype =        M_DEVT,
        .proto =        SYSREF_PROTO_DEV,
        .offset =       offsetof(struct cdev, si_sysref),
        .objsize =      sizeof(struct cdev),
        .mag_capacity = 32,
        .flags =        0,
        .ops =  {
                .terminate = (sysref_terminate_func_t)cdev_terminate
        }
};

/*
 * This is the number of hash-buckets.  Experiements with 'real-life'
 * udev_t's show that a prime halfway between two powers of two works
 * best.
 */
#define DEVT_HASH 128   /* must be power of 2 */
static LIST_HEAD(, cdev) dev_hash[DEVT_HASH];

static int free_devt;
SYSCTL_INT(_debug, OID_AUTO, free_devt, CTLFLAG_RW, &free_devt, 0, "");
int dev_ref_debug = 0;
SYSCTL_INT(_debug, OID_AUTO, dev_refs, CTLFLAG_RW, &dev_ref_debug, 0, "");

/*
 * cdev_t and u_dev_t primitives.  Note that the major number is always
 * extracted from si_umajor, not from si_devsw, because si_devsw is replaced
 * when a device is destroyed.
 */
int
major(cdev_t dev)
{
        if (dev == NULL)
                return NOUDEV;
        return(dev->si_umajor);
}

int
minor(cdev_t dev)
{
        if (dev == NULL)
                return NOUDEV;
        return(dev->si_uminor);
}

/*
 * Compatibility function with old udev_t format to convert the
 * non-consecutive minor space into a consecutive minor space.
 */
int
lminor(cdev_t dev)
{
        int y;

        if (dev == NULL)
                return NOUDEV;
        y = dev->si_uminor;
        if (y & 0x0000ff00)
                return NOUDEV;
        return ((y & 0xff) | (y >> 8));
}

/*
 * This is a bit complex because devices are always created relative to
 * a particular cdevsw, including 'hidden' cdevsw's (such as the raw device
 * backing a disk subsystem overlay), so we have to compare both the
 * devsw and udev fields to locate the correct device.
 *
 * The device is created if it does not already exist.  If SI_ADHOC is not
 * set the device will be referenced (once) and SI_ADHOC will be set.
 * The caller must explicitly add additional references to the device if
 * the caller wishes to track additional references.
 *
 * NOTE: The passed ops vector must normally match the device.  This is
 * because the kernel may create shadow devices that are INVISIBLE TO
 * USERLAND.  For example, the block device backing a disk is created
 * as a shadow underneath the user-visible disklabel management device.
 * Sometimes a device ops vector can be overridden, such as by /dev/console.
 * In this case and this case only we allow a match when the ops vector
 * otherwise would not match.
 */
static
int
__devthash(int x, int y)
{
        return(((x << 2) ^ y) & (DEVT_HASH - 1));
}

static
cdev_t
hashdev(struct dev_ops *ops, int x, int y, int allow_intercept)
{
        struct cdev *si;
        int hash;

        hash = __devthash(x, y);
        LIST_FOREACH(si, &dev_hash[hash], si_hash) {
                if (si->si_umajor == x && si->si_uminor == y) {
                        if (si->si_ops == ops)
                                return (si);
                        if (allow_intercept && (si->si_flags & SI_INTERCEPTED))
                                return (si);
                }
        }
        si = sysref_alloc(&cdev_sysref_class);
        si->si_ops = ops;
        si->si_flags |= SI_HASHED | SI_ADHOC;
        si->si_umajor = x;
        si->si_uminor = y;
        LIST_INSERT_HEAD(&dev_hash[hash], si, si_hash);
        sysref_activate(&si->si_sysref);

        dev_dclone(si);
        if (ops != &dead_dev_ops)
                ++ops->head.refs;
        if (dev_ref_debug) {
                kprintf("create    dev %p %s(minor=%08x) refs=%d\n", 
                        si, devtoname(si), y,
                        si->si_sysref.refcnt);
        }
        return (si);
}

/*
 * Convert a device pointer to an old style device number.  Return NOUDEV
 * if the device is invalid or if the device (maj,min) cannot be converted
 * to an old style udev_t.
 */
udev_t
dev2udev(cdev_t dev)
{
        if (dev == NULL)
                return NOUDEV;
        if ((dev->si_umajor & 0xffffff00) ||
            (dev->si_uminor & 0x0000ff00)) {
                return NOUDEV;
        }
        return((dev->si_umajor << 8) | dev->si_uminor);
}

/*
 * Convert a device number to a device pointer.  The device is referenced
 * ad-hoc, meaning that the caller should call reference_dev() if it wishes
 * to keep ahold of the returned structure long term.
 *
 * The returned device is associated with the currently installed cdevsw
 * for the requested major number.  NULL is returned if the major number
 * has not been registered.
 */
cdev_t
udev2dev(udev_t x, int b)
{
        cdev_t dev;
        struct dev_ops *ops;

        if (x == NOUDEV || b != 0)
                return(NULL);
        ops = dev_ops_get(umajor(x), uminor(x));
        if (ops == NULL)
                return(NULL);
        dev = hashdev(ops, umajor(x), uminor(x), TRUE);
        return(dev);
}

int
dev_is_good(cdev_t dev)
{
        if (dev != NULL && dev->si_ops != &dead_dev_ops)
                return(1);
        return(0);
}

/*
 * Various user device number extraction and conversion routines
 */
int
uminor(udev_t dev)
{
        if (dev == NOUDEV)
                return(-1);
        return(dev & 0xffff00ff);
}

int
umajor(udev_t dev)
{
        if (dev == NOUDEV)
                return(-1);
        return((dev & 0xff00) >> 8);
}

udev_t
makeudev(int x, int y)
{
        if ((x & 0xffffff00) || (y & 0x0000ff00))
                return NOUDEV;
        return ((x << 8) | y);
}

/*
 * Create an internal or external device.
 *
 * Device majors can be overloaded and used directly by the kernel without
 * conflict, but userland will only see the particular device major that
 * has been installed with dev_ops_add().
 *
 * This routine creates and returns an unreferenced ad-hoc entry for the
 * device which will remain intact until the device is destroyed.  If the
 * caller intends to store the device pointer it must call reference_dev()
 * to retain a real reference to the device.
 *
 * If an entry already exists, this function will set (or override)
 * its cred requirements and name (XXX DEVFS interface).
 */
cdev_t
make_dev(struct dev_ops *ops, int minor, uid_t uid, gid_t gid, 
        int perms, const char *fmt, ...)
{
        cdev_t  dev;
        __va_list ap;
        int i;

        /*
         * compile the cdevsw and install the device
         */
        compile_dev_ops(ops);
        dev = hashdev(ops, ops->head.maj, minor, FALSE);

        /*
         * Set additional fields (XXX DEVFS interface goes here)
         */
        __va_start(ap, fmt);
        i = kvcprintf(fmt, NULL, dev->si_name, 32, ap);
        dev->si_name[i] = '\0';
        __va_end(ap);

        return (dev);
}

/*
 * This function is similar to make_dev() but no cred information or name
 * need be specified.
 */
cdev_t
make_adhoc_dev(struct dev_ops *ops, int minor)
{
        cdev_t dev;

        dev = hashdev(ops, ops->head.maj, minor, FALSE);
        return(dev);
}

/*
 * This function is similar to make_dev() except the new device is created
 * using an old device as a template.
 */
cdev_t
make_sub_dev(cdev_t odev, int minor)
{
        cdev_t  dev;

        dev = hashdev(odev->si_ops, odev->si_umajor, minor, FALSE);

        /*
         * Copy cred requirements and name info XXX DEVFS.
         */
        if (dev->si_name[0] == 0 && odev->si_name[0])
                bcopy(odev->si_name, dev->si_name, sizeof(dev->si_name));
        return (dev);
}

cdev_t
get_dev(int x, int y)
{
        cdev_t dev;
        struct dev_ops *ops;

        if (x == NOUDEV)
                return(NULL);
        ops = dev_ops_get(x, y);
        if (ops == NULL)
                return(NULL);
        dev = hashdev(ops, x, y, TRUE);
        return(dev);
}

/*
 * destroy_dev() removes the adhoc association for a device and revectors
 * its ops to &dead_dev_ops.
 *
 * This routine releases the reference count associated with the ADHOC
 * entry, plus releases the reference count held by the caller.  What this
 * means is that you should not call destroy_dev(make_dev(...)), because
 * make_dev() does not bump the reference count (beyond what it needs to
 * create the ad-hoc association).  Any procedure that intends to destroy
 * a device must have its own reference to it first.
 */
void
destroy_dev(cdev_t dev)
{
        int hash;

        if (dev == NULL)
                return;
        if ((dev->si_flags & SI_ADHOC) == 0) {
                release_dev(dev);
                return;
        }
        if (dev_ref_debug) {
                kprintf("destroy   dev %p %s(minor=%08x) refs=%d\n", 
                        dev, devtoname(dev), dev->si_uminor,
                        dev->si_sysref.refcnt);
        }
        if (dev->si_sysref.refcnt < 2) {
                kprintf("destroy_dev(): too few references on device! "
                        "%p %s(minor=%08x) refs=%d\n",
                    dev, devtoname(dev), dev->si_uminor,
                    dev->si_sysref.refcnt);
        }
        dev->si_flags &= ~SI_ADHOC;
        if (dev->si_flags & SI_HASHED) {
                hash = __devthash(dev->si_umajor, dev->si_uminor);
                LIST_REMOVE(dev, si_hash);
                dev->si_flags &= ~SI_HASHED;
        }

        /*
         * We have to release the ops reference before we replace the
         * device switch with dead_dev_ops.
         */
        if (dead_dev_ops.d_strategy == NULL)
                compile_dev_ops(&dead_dev_ops);
        if (dev->si_ops && dev->si_ops != &dead_dev_ops)
                dev_ops_release(dev->si_ops);
        dev->si_drv1 = NULL;
        dev->si_drv2 = NULL;
        dev->si_ops = &dead_dev_ops;
        sysref_put(&dev->si_sysref);    /* release adhoc association */
        release_dev(dev);               /* release callers reference */
}

/*
 * Destroy all ad-hoc device associations associated with a domain within a
 * device switch.  Only the minor numbers are included in the mask/match
 * values. 
 *
 * Unlike the ops functions whos link structures do not contain
 * any major bits, this function scans through the dev list via
 * si_umajor/si_uminor.
 *
 * The caller must not include any major bits in the match value.
 */
void
destroy_all_devs(struct dev_ops *ops, u_int mask, u_int match)
{
        int i;
        cdev_t dev;
        cdev_t ndev;

        for (i = 0; i < DEVT_HASH; ++i) {
                ndev = LIST_FIRST(&dev_hash[i]);
                while ((dev = ndev) != NULL) {
                    ndev = LIST_NEXT(dev, si_hash);
                    KKASSERT(dev->si_flags & SI_ADHOC);
                    if (dev->si_ops == ops && 
                        ((u_int)dev->si_uminor & mask) == match
                    ) {
                        reference_dev(dev);
                        destroy_dev(dev);
                    }
                }
        }
}

/*
 * Add a reference to a device.  Callers generally add their own references
 * when they are going to store a device node in a variable for long periods
 * of time, to prevent a disassociation from free()ing the node.
 *
 * Also note that a caller that intends to call destroy_dev() must first
 * obtain a reference on the device.  The ad-hoc reference you get with
 * make_dev() and friends is NOT sufficient to be able to call destroy_dev().
 */
cdev_t
reference_dev(cdev_t dev)
{
        if (dev != NULL) {
                sysref_get(&dev->si_sysref);
                if (dev_ref_debug) {
                        kprintf("reference dev %p %s(minor=%08x) refs=%d\n", 
                            dev, devtoname(dev), dev->si_uminor,
                            dev->si_sysref.refcnt);
                }
        }
        return(dev);
}

/*
 * release a reference on a device.  The device will be terminated when the
 * last reference has been released.
 *
 * NOTE: we must use si_umajor to figure out the original major number,
 * because si_ops could already be pointing at dead_dev_ops.
 */
void
release_dev(cdev_t dev)
{
        if (dev == NULL)
                return;
        sysref_put(&dev->si_sysref);
}

static
void
cdev_terminate(struct cdev *dev)
{
        int messedup = 0;

        if (dev_ref_debug) {
                kprintf("release   dev %p %s(minor=%08x) refs=%d\n", 
                        dev, devtoname(dev), dev->si_uminor,
                        dev->si_sysref.refcnt);
        }
        if (dev->si_flags & SI_ADHOC) {
                kprintf("Warning: illegal final release on ADHOC"
                        " device %p(%s), the device was never"
                        " destroyed!\n",
                        dev, devtoname(dev));
                messedup = 1;
        }
        if (dev->si_flags & SI_HASHED) {
                kprintf("Warning: last release on device, no call"
                        " to destroy_dev() was made! dev %p(%s)\n",
                        dev, devtoname(dev));
                reference_dev(dev);
                destroy_dev(dev);
                messedup = 1;
        }
        if (SLIST_FIRST(&dev->si_hlist) != NULL) {
                kprintf("Warning: last release on device, vnode"
                        " associations still exist! dev %p(%s)\n",
                        dev, devtoname(dev));
                messedup = 1;
        }
        if (dev->si_ops && dev->si_ops != &dead_dev_ops) {
                dev_ops_release(dev->si_ops);
                dev->si_ops = NULL;
        }
        if (messedup == 0) 
                sysref_put(&dev->si_sysref);
}

const char *
devtoname(cdev_t dev)
{
        int mynor;
        int len;
        char *p;
        const char *dname;

        if (dev == NULL)
                return("#nodev");
        if (dev->si_name[0] == '#' || dev->si_name[0] == '\0') {
                p = dev->si_name;
                len = sizeof(dev->si_name);
                if ((dname = dev_dname(dev)) != NULL)
                        ksnprintf(p, len, "#%s/", dname);
                else
                        ksnprintf(p, len, "#%d/", major(dev));
                len -= strlen(p);
                p += strlen(p);
                mynor = minor(dev);
                if (mynor < 0 || mynor > 255)
                        ksnprintf(p, len, "%#x", (u_int)mynor);
                else
                        ksnprintf(p, len, "%d", mynor);
        }
        return (dev->si_name);
}