sound: Retire unit.*

The unit.* code is largely obsolete and imposes limits that are no
longer needed nowadays.

- Capping the maximum allowed soundcards in a given machine. By default,
  the limit is 512 (snd_max_u() in unit.c), and the maximum possible is
  2048 (SND_UNIT_UMAX in unit.h). It can also be tuned through the
  hw.snd.maxunit loader(8) tunable. Even though these limits are large
  enough that they should never cause problems, there is no need for
  this limit to exist in the first place.
- Capping the available device/channel types. By default, this is 32
  (snd_max_d() in unit.c). However, these types are pre-defined in
  pcm/sound.h (see SND_DEV_*), so the cap is unnecessary when we know
  that their number is constant.
- Capping the number of channels per-device. By default, the limit 1024
  (snd_max_c() in unit.c). This is probably the most problematic of the
  limits mentioned, because this limit can never be reached, as the
  maximum is hard-capped at either hw.snd.maxautovchans (16 by default),
  or SND_MAXHWCHAN and SND_MAXVCHANS.

These limtits are encoded in masks (see SND_U_MASK, SND_D_MASK,
SND_C_MASK in unit.h) and are used to construct a bitfield of the form
[dsp_unit, type, channel_unit] in snd_mkunit() which is assigned to
pcm_channel->unit.

This patch gets rid of everything unit.*-related and makes a slightly
different use of the "unit" field to only contain the channel unit
number. The channel type is stored in a new pcm_channel->type field, and
the DSP unit number need not be stored at all, since we can fetch it
from device_get_unit(pcm_channel->dev). This change has the effect that
we no longer need to impose caps on the number of soundcards,
device/channel types and per-device channels. As a result the code is
noticeably simplified and more readable.

Apart from the fact that the hw.snd.maxunit loader(8) tunable is also
retired as a side-effect of this patch, sound(4)'s behavior remains the
same.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Reviewed by:	dev_submerge.ch
Differential Revision:	https://reviews.freebsd.org/D44912

13 files changed, 74 insertions, 454 deletions

diff --git a/RELNOTES b/RELNOTES
index 91d6d74a38fc..658a82a9e1b0 100644
--- a/RELNOTES
+++ b/RELNOTES
@@ -10,6 +10,9 @@ newline.  Entries should be separated by a newline.
 
 Changes to this file should not be MFCed.
 
+8fef193e14e2:
+	As a side-effect of retiring the unit.* code in sound(4), the
+	hw.snd.maxunit loader(8) tunable is also retired.
 6d5ce2bb6344:
 	The default value of the nfs_reserved_port_only rc.conf(5) setting has
 	changed.  The FreeBSD NFS server now requires the source port of
diff --git a/sys/conf/files b/sys/conf/files
index 29c02a503027..ef0a56eb8b45 100644
--- a/sys/conf/files
+++ b/sys/conf/files
@@ -3072,7 +3072,6 @@ dev/smc/if_smc.c		optional smc
 dev/smc/if_smc_acpi.c		optional smc acpi
 dev/smc/if_smc_fdt.c		optional smc fdt
 dev/snp/snp.c			optional snp
-dev/sound/unit.c		optional sound
 dev/sound/pci/als4000.c		optional snd_als4000 pci
 dev/sound/pci/atiixp.c		optional snd_atiixp pci
 dev/sound/pci/cmi.c		optional snd_cmi pci
diff --git a/sys/dev/sound/pcm/channel.h b/sys/dev/sound/pcm/channel.h
index c8d33c583188..d4f73275ed39 100644
--- a/sys/dev/sound/pcm/channel.h
+++ b/sys/dev/sound/pcm/channel.h
@@ -104,6 +104,7 @@ struct pcm_channel {
 	void *devinfo;
 	device_t dev;
 	int unit;
+	int type;
 	char name[CHN_NAMELEN];
 	char comm[MAXCOMLEN + 1];
 	struct mtx *lock;
@@ -224,7 +225,7 @@ struct pcm_channel {
 #define CHN_INSERT_SORT(w, x, y, z)		do {			\
 	struct pcm_channel *t, *a = NULL;				\
 	CHN_FOREACH(t, x, z) {						\
-		if ((y)->unit w t->unit)				\
+		if ((y)->type w t->type)				\
 			a = t;						\
 		else							\
 			break;						\
@@ -235,13 +236,9 @@ struct pcm_channel {
 		CHN_INSERT_HEAD(x, y, z);				\
 } while (0)
 
-#define CHN_INSERT_SORT_ASCEND(x, y, z)		CHN_INSERT_SORT(>, x, y, z)
+#define CHN_INSERT_SORT_ASCEND(x, y, z)		CHN_INSERT_SORT(>=, x, y, z)
 #define CHN_INSERT_SORT_DESCEND(x, y, z)	CHN_INSERT_SORT(<, x, y, z)
 
-#define CHN_UNIT(x)	(snd_unit2u((x)->unit))
-#define CHN_DEV(x)	(snd_unit2d((x)->unit))
-#define CHN_CHAN(x)	(snd_unit2c((x)->unit))
-
 #define CHN_BUF_PARENT(x, y)						\
 	(((x) != NULL && (x)->parentchannel != NULL &&			\
 	(x)->parentchannel->bufhard != NULL) ?				\
diff --git a/sys/dev/sound/pcm/dsp.c b/sys/dev/sound/pcm/dsp.c
index df1482d6a97a..448ecb183298 100644
--- a/sys/dev/sound/pcm/dsp.c
+++ b/sys/dev/sound/pcm/dsp.c
@@ -444,7 +444,7 @@ dsp_open(struct cdev *i_dev, int flags, int mode, struct thread *td)
 	if (DSP_F_READ(flags)) {
 		/* open for read */
 		rderror = pcm_chnalloc(d, &rdch, PCMDIR_REC,
-		    td->td_proc->p_pid, td->td_proc->p_comm, -1);
+		    td->td_proc->p_pid, td->td_proc->p_comm);
 
 		if (rderror == 0 && chn_reset(rdch, fmt, spd) != 0)
 			rderror = ENXIO;
@@ -472,7 +472,7 @@ dsp_open(struct cdev *i_dev, int flags, int mode, struct thread *td)
 	if (DSP_F_WRITE(flags)) {
 		/* open for write */
 		wrerror = pcm_chnalloc(d, &wrch, PCMDIR_PLAY,
-		    td->td_proc->p_pid, td->td_proc->p_comm, -1);
+		    td->td_proc->p_pid, td->td_proc->p_comm);
 
 		if (wrerror == 0 && chn_reset(wrch, fmt, spd) != 0)
 			wrerror = ENXIO;
@@ -630,68 +630,12 @@ dsp_write(struct cdev *i_dev, struct uio *buf, int flag)
 }
 
 static int
-dsp_get_volume_channel(struct dsp_cdevpriv *priv, struct pcm_channel **volch)
-{
-	struct snddev_info *d;
-	struct pcm_channel *c;
-	int unit;
-
-	KASSERT(volch != NULL,
-	    ("%s(): NULL query priv=%p volch=%p", __func__, priv, volch));
-
-	d = priv->sc;
-	if (!PCM_REGISTERED(d)) {
-		*volch = NULL;
-		return (EINVAL);
-	}
-
-	PCM_UNLOCKASSERT(d);
-
-	*volch = NULL;
-
-	c = priv->volch;
-	if (c != NULL) {
-		if (!(c->feederflags & (1 << FEEDER_VOLUME)))
-			return (-1);
-		*volch = c;
-		return (0);
-	}
-
-	PCM_LOCK(d);
-	PCM_WAIT(d);
-	PCM_ACQUIRE(d);
-
-	unit = dev2unit(d->dsp_dev);
-
-	CHN_FOREACH(c, d, channels.pcm) {
-		CHN_LOCK(c);
-		if (c->unit != unit) {
-			CHN_UNLOCK(c);
-			continue;
-		}
-		*volch = c;
-		pcm_chnref(c, 1);
-		priv->volch = c;
-		CHN_UNLOCK(c);
-		PCM_RELEASE(d);
-		PCM_UNLOCK(d);
-		return ((c->feederflags & (1 << FEEDER_VOLUME)) ? 0 : -1);
-	}
-
-	PCM_RELEASE(d);
-	PCM_UNLOCK(d);
-
-	return (EINVAL);
-}
-
-static int
 dsp_ioctl_channel(struct dsp_cdevpriv *priv, struct pcm_channel *volch,
     u_long cmd, caddr_t arg)
 {
 	struct snddev_info *d;
 	struct pcm_channel *rdch, *wrch;
-	int j, devtype, ret;
-	int left, right, center, mute;
+	int j, left, right, center, mute;
 
 	d = priv->sc;
 	if (!PCM_REGISTERED(d) || !(pcm_getflags(d->dev) & SD_F_VPC))
@@ -716,19 +660,6 @@ dsp_ioctl_channel(struct dsp_cdevpriv *priv, struct pcm_channel *volch,
 			volch = wrch;
 	}
 
-	devtype = PCMDEV(d->dsp_dev);
-
-	/* Look super harder */
-	if (volch == NULL &&
-	    (devtype == SND_DEV_DSPHW_PLAY || devtype == SND_DEV_DSPHW_VPLAY ||
-	    devtype == SND_DEV_DSPHW_REC || devtype == SND_DEV_DSPHW_VREC)) {
-		ret = dsp_get_volume_channel(priv, &volch);
-		if (ret != 0)
-			return (ret);
-		if (volch == NULL)
-			return (EINVAL);
-	}
-
 	/* Final validation */
 	if (volch == NULL)
 		return (EINVAL);
@@ -2105,8 +2036,6 @@ dsp_sysinit(void *p)
 {
 	if (dsp_ehtag != NULL)
 		return;
-	/* initialize unit numbering */
-	snd_unit_init();
 	dsp_ehtag = EVENTHANDLER_REGISTER(dev_clone, dsp_clone, 0, 1000);
 }
 
@@ -2123,20 +2052,19 @@ SYSINIT(dsp_sysinit, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, dsp_sysinit, NULL);
 SYSUNINIT(dsp_sysuninit, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, dsp_sysuninit, NULL);
 
 char *
-dsp_unit2name(char *buf, size_t len, int unit)
+dsp_unit2name(char *buf, size_t len, struct pcm_channel *ch)
 {
-	int i, dtype;
+	int i;
 
 	KASSERT(buf != NULL && len != 0,
 	    ("bogus buf=%p len=%ju", buf, (uintmax_t)len));
 
-	dtype = snd_unit2d(unit);
-
 	for (i = 0; i < nitems(dsp_cdevs); i++) {
-		if (dtype != dsp_cdevs[i].type || dsp_cdevs[i].alias != NULL)
+		if (ch->type != dsp_cdevs[i].type || dsp_cdevs[i].alias != NULL)
 			continue;
-		snprintf(buf, len, "%s%d%s%d", dsp_cdevs[i].name,
-		    snd_unit2u(unit), dsp_cdevs[i].sep, snd_unit2c(unit));
+		snprintf(buf, len, "%s%d%s%d",
+		    dsp_cdevs[i].name, device_get_unit(ch->dev),
+		    dsp_cdevs[i].sep, ch->unit);
 		return (buf);
 	}
 
@@ -2224,12 +2152,10 @@ dsp_oss_audioinfo(struct cdev *i_dev, oss_audioinfo *ai)
 				if (devfs_foreach_cdevpriv(i_dev,
 				    dsp_oss_audioinfo_cb, ch) != 0) {
 					devname = dsp_unit2name(buf,
-					    sizeof(buf), ch->unit);
+					    sizeof(buf), ch);
 				}
-			} else if (ai->dev == nchan) {
-				devname = dsp_unit2name(buf, sizeof(buf),
-				    ch->unit);
-			}
+			} else if (ai->dev == nchan)
+				devname = dsp_unit2name(buf, sizeof(buf), ch);
 			if (devname != NULL)
 				break;
 			CHN_UNLOCK(ch);
diff --git a/sys/dev/sound/pcm/dsp.h b/sys/dev/sound/pcm/dsp.h
index 6098c0641eb5..b81e60dc19b5 100644
--- a/sys/dev/sound/pcm/dsp.h
+++ b/sys/dev/sound/pcm/dsp.h
@@ -35,7 +35,7 @@ extern struct cdevsw dsp_cdevsw;
 
 int dsp_make_dev(device_t);
 void dsp_destroy_dev(device_t);
-char *dsp_unit2name(char *, size_t, int);
+char *dsp_unit2name(char *, size_t, struct pcm_channel *);
 int dsp_oss_audioinfo(struct cdev *, oss_audioinfo *);
 
 #endif /* !_PCMDSP_H_ */
diff --git a/sys/dev/sound/pcm/feeder.c b/sys/dev/sound/pcm/feeder.c
index 8278a85948a8..78443ad76140 100644
--- a/sys/dev/sound/pcm/feeder.c
+++ b/sys/dev/sound/pcm/feeder.c
@@ -82,9 +82,7 @@ feeder_register(void *p)
 		if (snd_verbose < 0 || snd_verbose > 4)
 			snd_verbose = 1;
 
-		/* initialize unit numbering */
-		snd_unit_init();
-		if (snd_unit < 0 || snd_unit > PCMMAXUNIT)
+		if (snd_unit < 0)
 			snd_unit = -1;
 		
 		if (snd_maxautovchans < 0 ||
diff --git a/sys/dev/sound/pcm/mixer.c b/sys/dev/sound/pcm/mixer.c
index 2f4a6f4d6395..3e197b120c9d 100644
--- a/sys/dev/sound/pcm/mixer.c
+++ b/sys/dev/sound/pcm/mixer.c
@@ -727,7 +727,7 @@ mixer_init(device_t dev, kobj_class_t cls, void *devinfo)
 	u_int16_t v;
 	struct cdev *pdev;
 	const char *name;
-	int i, unit, devunit, val;
+	int i, unit, val;
 
 	snddev = device_get_softc(dev);
 	if (snddev == NULL)
@@ -764,8 +764,7 @@ mixer_init(device_t dev, kobj_class_t cls, void *devinfo)
 
 	mixer_setrecsrc(m, 0); /* Set default input. */
 
-	devunit = snd_mkunit(unit, SND_DEV_CTL, 0);
-	pdev = make_dev(&mixer_cdevsw, devunit, UID_ROOT, GID_WHEEL, 0666,
+	pdev = make_dev(&mixer_cdevsw, SND_DEV_CTL, UID_ROOT, GID_WHEEL, 0666,
 	    "mixer%d", unit);
 	pdev->si_drv1 = m;
 	snddev->mixer_dev = pdev;
diff --git a/sys/dev/sound/pcm/sound.c b/sys/dev/sound/pcm/sound.c
index 0a88d732def7..c32536a55960 100644
--- a/sys/dev/sound/pcm/sound.c
+++ b/sys/dev/sound/pcm/sound.c
@@ -244,98 +244,63 @@ pcm_setvchans(struct snddev_info *d, int direction, int newcnt, int num)
 /* return error status and a locked channel */
 int
 pcm_chnalloc(struct snddev_info *d, struct pcm_channel **ch, int direction,
-    pid_t pid, char *comm, int devunit)
+    pid_t pid, char *comm)
 {
 	struct pcm_channel *c;
 	int err, vchancount, vchan_num;
+	bool retry;
 
-	KASSERT(d != NULL && ch != NULL && (devunit == -1 ||
-	    !(devunit & ~(SND_U_MASK | SND_D_MASK | SND_C_MASK))) &&
+	KASSERT(d != NULL && ch != NULL &&
 	    (direction == PCMDIR_PLAY || direction == PCMDIR_REC),
-	    ("%s(): invalid d=%p ch=%p direction=%d pid=%d devunit=%d",
-	    __func__, d, ch, direction, pid, devunit));
+	    ("%s(): invalid d=%p ch=%p direction=%d pid=%d",
+	    __func__, d, ch, direction, pid));
 	PCM_BUSYASSERT(d);
 
-	/* Double check again. */
-	if (devunit != -1) {
-		switch (snd_unit2d(devunit)) {
-		case SND_DEV_DSPHW_PLAY:
-		case SND_DEV_DSPHW_VPLAY:
-			if (direction != PCMDIR_PLAY)
-				return (ENOTSUP);
-			break;
-		case SND_DEV_DSPHW_REC:
-		case SND_DEV_DSPHW_VREC:
-			if (direction != PCMDIR_REC)
-				return (ENOTSUP);
-			break;
-		default:
-			if (!(direction == PCMDIR_PLAY ||
-			    direction == PCMDIR_REC))
-				return (ENOTSUP);
-			break;
-		}
-	}
-
 	*ch = NULL;
 	vchan_num = 0;
 	vchancount = (direction == PCMDIR_PLAY) ? d->pvchancount :
 	    d->rvchancount;
 
+	retry = false;
 retry_chnalloc:
 	err = ENOTSUP;
 	/* scan for a free channel */
 	CHN_FOREACH(c, d, channels.pcm) {
 		CHN_LOCK(c);
-		if (devunit == -1 && c->direction == direction &&
-		    (c->flags & CHN_F_VIRTUAL)) {
+		if (c->direction == direction && (c->flags & CHN_F_VIRTUAL)) {
 			if (vchancount < snd_maxautovchans &&
-			    vchan_num < CHN_CHAN(c)) {
+			    vchan_num < c->unit) {
 			    	CHN_UNLOCK(c);
 				goto vchan_alloc;
 			}
 			vchan_num++;
 		}
-		if (c->direction == direction && !(c->flags & CHN_F_BUSY) &&
-		    (devunit == -1 || devunit == -2 || c->unit == devunit)) {
+		if (c->direction == direction && !(c->flags & CHN_F_BUSY)) {
 			c->flags |= CHN_F_BUSY;
 			c->pid = pid;
 			strlcpy(c->comm, (comm != NULL) ? comm :
 			    CHN_COMM_UNKNOWN, sizeof(c->comm));
 			*ch = c;
 			return (0);
-		} else if (c->unit == devunit) {
-			if (c->direction != direction)
-				err = ENOTSUP;
-			else if (c->flags & CHN_F_BUSY)
-				err = EBUSY;
-			else
-				err = EINVAL;
-			CHN_UNLOCK(c);
-			return (err);
-		} else if ((devunit == -1 || devunit == -2) &&
-		    c->direction == direction && (c->flags & CHN_F_BUSY))
+		} else if (c->direction == direction && (c->flags & CHN_F_BUSY))
 			err = EBUSY;
 		CHN_UNLOCK(c);
 	}
 
-	if (devunit == -2)
+	/*
+	 * We came from retry_chnalloc and still didn't find a free channel.
+	 */
+	if (retry)
 		return (err);
 
 vchan_alloc:
 	/* no channel available */
-	if (devunit == -1 || snd_unit2d(devunit) == SND_DEV_DSPHW_VPLAY ||
-	    snd_unit2d(devunit) == SND_DEV_DSPHW_VREC) {
-		if (!(vchancount > 0 && vchancount < snd_maxautovchans) &&
-		    (devunit == -1 || snd_unit2c(devunit) < snd_maxautovchans))
-			return (err);
-		err = pcm_setvchans(d, direction, vchancount + 1,
-		    (devunit == -1) ? -1 : snd_unit2c(devunit));
-		if (err == 0) {
-			if (devunit == -1)
-				devunit = -2;
-			goto retry_chnalloc;
-		}
+	if (!(vchancount > 0 && vchancount < snd_maxautovchans))
+		return (err);
+	err = pcm_setvchans(d, direction, vchancount + 1, -1);
+	if (err == 0) {
+		retry = true;
+		goto retry_chnalloc;
 	}
 
 	return (err);
@@ -445,7 +410,7 @@ pcm_chn_create(struct snddev_info *d, struct pcm_channel *parent, kobj_class_t c
 {
 	struct pcm_channel *ch;
 	int direction, err, rpnum, *pnum, max;
-	int udc, device, chan;
+	int type, unit;
 	char *dirs, *devname, buf[CHN_NAMELEN];
 
 	PCM_BUSYASSERT(d);
@@ -457,56 +422,54 @@ pcm_chn_create(struct snddev_info *d, struct pcm_channel *parent, kobj_class_t c
 		dirs = "play";
 		direction = PCMDIR_PLAY;
 		pnum = &d->playcount;
-		device = SND_DEV_DSPHW_PLAY;
+		type = SND_DEV_DSPHW_PLAY;
 		max = SND_MAXHWCHAN;
 		break;
 	case PCMDIR_PLAY_VIRTUAL:
 		dirs = "virtual_play";
 		direction = PCMDIR_PLAY;
 		pnum = &d->pvchancount;
-		device = SND_DEV_DSPHW_VPLAY;
+		type = SND_DEV_DSPHW_VPLAY;
 		max = SND_MAXVCHANS;
 		break;
 	case PCMDIR_REC:
 		dirs = "record";
 		direction = PCMDIR_REC;
 		pnum = &d->reccount;
-		device = SND_DEV_DSPHW_REC;
+		type = SND_DEV_DSPHW_REC;
 		max = SND_MAXHWCHAN;
 		break;
 	case PCMDIR_REC_VIRTUAL:
 		dirs = "virtual_record";
 		direction = PCMDIR_REC;
 		pnum = &d->rvchancount;
-		device = SND_DEV_DSPHW_VREC;
+		type = SND_DEV_DSPHW_VREC;
 		max = SND_MAXVCHANS;
 		break;
 	default:
 		return (NULL);
 	}
 
-	chan = (num == -1) ? 0 : num;
+	unit = (num == -1) ? 0 : num;
 
-	if (*pnum >= max || chan >= max)
+	if (*pnum >= max || unit >= max)
 		return (NULL);
 
 	rpnum = 0;
 
 	CHN_FOREACH(ch, d, channels.pcm) {
-		if (CHN_DEV(ch) != device)
+		if (ch->type != type)
 			continue;
-		if (chan == CHN_CHAN(ch)) {
-			if (num != -1) {
-				device_printf(d->dev,
-				    "channel num=%d allocated!\n", chan);
-				return (NULL);
-			}
-			chan++;
-			if (chan >= max) {
-				device_printf(d->dev,
-				    "chan=%d > %d\n", chan, max);
-				return (NULL);
-			}
+		if (unit == ch->unit && num != -1) {
+			device_printf(d->dev,
+			    "channel num=%d allocated!\n", unit);
+			return (NULL);
+		}
+		unit++;
+		if (unit >= max) {
+			device_printf(d->dev,
+			    "chan=%d > %d\n", unit, max);
+			return (NULL);
 		}
 		rpnum++;
 	}
@@ -518,25 +481,24 @@ pcm_chn_create(struct snddev_info *d, struct pcm_channel *parent, kobj_class_t c
 		return (NULL);
 	}
 
-	udc = snd_mkunit(device_get_unit(d->dev), device, chan);
-	devname = dsp_unit2name(buf, sizeof(buf), udc);
-
-	if (devname == NULL) {
-		device_printf(d->dev,
-		    "Failed to query device name udc=0x%08x\n", udc);
-		return (NULL);
-	}
-
 	PCM_UNLOCK(d);
 	ch = malloc(sizeof(*ch), M_DEVBUF, M_WAITOK | M_ZERO);
 	ch->methods = kobj_create(cls, M_DEVBUF, M_WAITOK | M_ZERO);
-	ch->unit = udc;
+	ch->type = type;
+	ch->unit = unit;
 	ch->pid = -1;
 	strlcpy(ch->comm, CHN_COMM_UNUSED, sizeof(ch->comm));
 	ch->parentsnddev = d;
 	ch->parentchannel = parent;
 	ch->dev = d->dev;
 	ch->trigger = PCMTRIG_STOP;
+	devname = dsp_unit2name(buf, sizeof(buf), ch);
+	if (devname == NULL) {
+		device_printf(d->dev, "Failed to query device name");
+		kobj_delete(ch->methods, M_DEVBUF);
+		free(ch, M_DEVBUF);
+		return (NULL);
+	}
 	snprintf(ch->name, sizeof(ch->name), "%s:%s:%s",
 	    device_get_nameunit(ch->dev), dirs, devname);
 
@@ -585,7 +547,7 @@ pcm_chn_add(struct snddev_info *d, struct pcm_channel *ch)
 
 	CHN_INSERT_SORT_ASCEND(d, ch, channels.pcm);
 
-	switch (CHN_DEV(ch)) {
+	switch (ch->type) {
 	case SND_DEV_DSPHW_PLAY:
 		d->playcount++;
 		break;
@@ -625,7 +587,7 @@ pcm_chn_remove(struct snddev_info *d, struct pcm_channel *ch)
 
 	CHN_REMOVE(d, ch, channels.pcm);
 
-	switch (CHN_DEV(ch)) {
+	switch (ch->type) {
 	case SND_DEV_DSPHW_PLAY:
 		d->playcount--;
 		break;
@@ -939,14 +901,6 @@ pcm_register(device_t dev, void *devinfo, int numplay, int numrec)
 		return EINVAL;
 	}
 
-	if (device_get_unit(dev) > PCMMAXUNIT) {
-		device_printf(dev, "PCMMAXUNIT reached : unit=%d > %d\n",
-		    device_get_unit(dev), PCMMAXUNIT);
-		device_printf(dev,
-		    "Use 'hw.snd.maxunit' tunable to raise the limit.\n");
-		return ENODEV;
-	}
-
 	d = device_get_softc(dev);
 	d->dev = dev;
 	d->lock = snd_mtxcreate(device_get_nameunit(dev), "sound cdev");
diff --git a/sys/dev/sound/pcm/sound.h b/sys/dev/sound/pcm/sound.h
index fe310a3be3d6..1f2dda880742 100644
--- a/sys/dev/sound/pcm/sound.h
+++ b/sys/dev/sound/pcm/sound.h
@@ -88,7 +88,6 @@ struct snd_mixer;
 #include <dev/sound/pcm/feeder.h>
 #include <dev/sound/pcm/mixer.h>
 #include <dev/sound/pcm/dsp.h>
-#include <dev/sound/unit.h>
 
 #define	PCM_SOFTC_SIZE	(sizeof(struct snddev_info))
 
@@ -101,21 +100,6 @@ struct snd_mixer;
 #define SOUND_MAXVER	SOUND_MODVER
 
 /*
- * We're abusing the fact that MAXMINOR still have enough room
- * for our bit twiddling and nobody ever need 512 unique soundcards,
- * 32 unique device types and 1024 unique cloneable devices for the
- * next 100 years...
- */
-
-#define PCMMAXUNIT		(snd_max_u())
-#define PCMMAXDEV		(snd_max_d())
-#define PCMMAXCHAN		(snd_max_c())
-
-#define PCMUNIT(x)		(snd_unit2u(dev2unit(x)))
-#define PCMDEV(x)		(snd_unit2d(dev2unit(x)))
-#define PCMCHAN(x)		(snd_unit2c(dev2unit(x)))
-
-/*
  * By design, limit possible channels for each direction.
  */
 #define SND_MAXHWCHAN		256
@@ -311,7 +295,7 @@ SYSCTL_DECL(_hw_snd);
 
 int pcm_setvchans(struct snddev_info *d, int direction, int newcnt, int num);
 int pcm_chnalloc(struct snddev_info *d, struct pcm_channel **ch, int direction,
-    pid_t pid, char *comm, int devunit);
+    pid_t pid, char *comm);
 int pcm_chnrelease(struct pcm_channel *c);
 int pcm_chnref(struct pcm_channel *c, int ref);
 
diff --git a/sys/dev/sound/pcm/vchan.c b/sys/dev/sound/pcm/vchan.c
index d10c3ff4aabb..ac5a0535ddce 100644
--- a/sys/dev/sound/pcm/vchan.c
+++ b/sys/dev/sound/pcm/vchan.c
@@ -923,7 +923,7 @@ vchan_sync(struct pcm_channel *c)
 	if (snd_passthrough_verbose != 0) {
 		char *devname, buf[CHN_NAMELEN];
 
-		devname = dsp_unit2name(buf, sizeof(buf), c->unit);
+		devname = dsp_unit2name(buf, sizeof(buf), c);
 		device_printf(c->dev,
 		    "%s(%s/%s) %s() -> re-sync err=%d\n",
 		    __func__, (devname != NULL) ? devname : "dspX", c->comm,
diff --git a/sys/dev/sound/unit.c b/sys/dev/sound/unit.c
deleted file mode 100644
index 28ffbde1f7ec..000000000000
--- a/sys/dev/sound/unit.c
+++ /dev/null
@@ -1,188 +0,0 @@
-/*-
- * SPDX-License-Identifier: BSD-2-Clause
- *
- * Copyright (c) 2007 Ariff Abdullah <ariff@FreeBSD.org>
- * 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/param.h>
-#include <sys/systm.h>
-
-#ifdef HAVE_KERNEL_OPTION_HEADERS
-#include "opt_snd.h"
-#endif
-
-#include <dev/sound/unit.h>
-
-/*
- * Unit magic allocator for sound driver.
- *
- * 'u' = Unit of attached soundcards
- * 'd' = Device type
- * 'c' = Channel number
- *
- * eg: dsp0.p1  - u=0, d=p, c=1
- *     dsp1.vp0 - u=1, d=vp, c=0
- *
- * Maximum unit of soundcards can be tuned through "hw.snd.maxunit", which is
- * between SND_UNIT_UMIN (16) and SND_UNIT_UMAX (2048). By design, the maximum
- * allowable allocated channel is 256.
- */
-
-/* Default width */
-static int snd_u_shift = 9;	/* 0 - 0x1ff :  512 distinct soundcards   */
-static int snd_d_shift = 5;	/* 0 - 0x1f  :   32 distinct device types */
-static int snd_c_shift = 10;	/* 0 - 0x3ff : 1024 distinct channels
-					       (256 limit "by design")	  */
-
-static int snd_unit_initialized = 0;
-
-#ifdef SND_DIAGNOSTIC
-#define SND_UNIT_ASSERT()	do {					\
-	if (snd_unit_initialized == 0)					\
-		panic("%s(): Uninitialized sound unit!", __func__);	\
-} while (0)
-#else
-#define SND_UNIT_ASSERT()	KASSERT(snd_unit_initialized != 0,	\
-				("%s(): Uninitialized sound unit!",	\
-				__func__))
-#endif
-
-#define MKMASK(x)	((1 << snd_##x##_shift) - 1)
-
-int
-snd_max_u(void)
-{
-	SND_UNIT_ASSERT();
-
-	return (MKMASK(u));
-}
-
-int
-snd_max_d(void)
-{
-	SND_UNIT_ASSERT();
-
-	return (MKMASK(d));
-}
-
-int
-snd_max_c(void)
-{
-	SND_UNIT_ASSERT();
-
-	return (MKMASK(c));
-}
-
-int
-snd_unit2u(int unit)
-{
-	SND_UNIT_ASSERT();
-
-	return ((unit >> (snd_c_shift + snd_d_shift)) & MKMASK(u));
-}
-
-int
-snd_unit2d(int unit)
-{
-	SND_UNIT_ASSERT();
-
-	return ((unit >> snd_c_shift) & MKMASK(d));
-}
-
-int
-snd_unit2c(int unit)
-{
-	SND_UNIT_ASSERT();
-
-	return (unit & MKMASK(c));
-}
-
-int
-snd_u2unit(int u)
-{
-	SND_UNIT_ASSERT();
-
-	return ((u & MKMASK(u)) << (snd_c_shift + snd_d_shift));
-}
-
-int
-snd_d2unit(int d)
-{
-	SND_UNIT_ASSERT();
-
-	return ((d & MKMASK(d)) << snd_c_shift);
-}
-
-int
-snd_c2unit(int c)
-{
-	SND_UNIT_ASSERT();
-
-	return (c & MKMASK(c));
-}
-
-int
-snd_mkunit(int u, int d, int c)
-{
-	SND_UNIT_ASSERT();
-
-	return ((c & MKMASK(c)) | ((d & MKMASK(d)) << snd_c_shift) |
-	    ((u & MKMASK(u)) << (snd_c_shift + snd_d_shift)));
-}
-
-/*
- * This *must* be called first before any of the functions above!!!
- */
-void
-snd_unit_init(void)
-{
-	int i;
-
-	if (snd_unit_initialized != 0)
-		return;
-
-	snd_unit_initialized = 1;
-
-	if (getenv_int("hw.snd.maxunit", &i) != 0) {
-		if (i < SND_UNIT_UMIN)
-			i = SND_UNIT_UMIN;
-		else if (i > SND_UNIT_UMAX)
-			i = SND_UNIT_UMAX;
-		else
-			i = roundup2(i, 2);
-
-		for (snd_u_shift = 0; (i >> (snd_u_shift + 1)) != 0;
-		    snd_u_shift++)
-			;
-
-		/* Make room for channels to fit within 24bit MAXMINOR limit. */
-		snd_c_shift = 24 - snd_u_shift - snd_d_shift;
-	}
-
-	if (bootverbose != 0)
-		printf("%s() u=0x%08x [%d] d=0x%08x [%d] c=0x%08x [%d]\n",
-		    __func__, SND_U_MASK, snd_max_u() + 1,
-		    SND_D_MASK, snd_max_d() + 1, SND_C_MASK, snd_max_c() + 1);
-}
diff --git a/sys/dev/sound/unit.h b/sys/dev/sound/unit.h
deleted file mode 100644
index 9ddd68a2fe04..000000000000
--- a/sys/dev/sound/unit.h
+++ /dev/null
@@ -1,52 +0,0 @@
-/*-
- * SPDX-License-Identifier: BSD-2-Clause
- *
- * Copyright (c) 2007 Ariff Abdullah <ariff@FreeBSD.org>
- * 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.
- */
-
-#ifndef _SND_UNIT_H_
-#define _SND_UNIT_H_
-
-#define SND_UNIT_UMIN	16
-#define SND_UNIT_UMAX	2048
-
-int snd_max_u(void);
-int snd_max_d(void);
-int snd_max_c(void);
-int snd_unit2u(int);
-int snd_unit2d(int);
-int snd_unit2c(int);
-int snd_u2unit(int);
-int snd_d2unit(int);
-int snd_c2unit(int);
-int snd_mkunit(int, int, int);
-
-void snd_unit_init(void);
-
-#define SND_U_MASK	(snd_u2unit(snd_max_u()))
-#define SND_D_MASK	(snd_d2unit(snd_max_d()))
-#define SND_C_MASK	(snd_c2unit(snd_max_c()))
-
-#endif /* !_SND_UNIT_H_ */
diff --git a/sys/modules/sound/sound/Makefile b/sys/modules/sound/sound/Makefile
index 833330ef9b26..1c3685715503 100644
--- a/sys/modules/sound/sound/Makefile
+++ b/sys/modules/sound/sound/Makefile
@@ -17,7 +17,7 @@ SRCS+=	feeder_eq_gen.h feeder_rate_gen.h snd_fxdiv_gen.h
 SRCS+=	mpu_if.h mpufoi_if.h synth_if.h
 SRCS+=	mpu_if.c mpufoi_if.c synth_if.c
 SRCS+=	ac97.c ac97_patch.c buffer.c channel.c dsp.c
-SRCS+=	mixer.c sndstat.c sound.c unit.c vchan.c
+SRCS+=	mixer.c sndstat.c sound.c vchan.c
 SRCS+=	midi.c mpu401.c sequencer.c
 
 feeder_eq_gen.h:	${SYSDIR}/tools/sound/feeder_eq_mkfilter.awk