sound: Retire mixer_ioctl_channel()

This function never succeeds when it is not called from the same process
that has opened the file descriptor (e.g., mixer(8)). The reason is that
the CHN_FOREACH() loop tries to match the pid of each channel with the
pid of the process performing the ioctl, which will not be the same,
unless it's the same process that both opened the channel and performed
the ioctl.

In the case that the same process opens the channels and performs the
ioctl, however, we still do not need to worry, because mixer_ioctl_cmd()
essentially does the same thing anyway. Additionally, this scenario
should be quite rare, given that most applications do not open both
/dev/dsp* and /dev/mixer*, and in fact, it is actively encouraged by the
official OSSv4 specification not to do that.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Pull Request:	https://ron-dev.freebsd.org/FreeBSD/src/pulls/18

1 files changed, 1 insertions, 116 deletions

diff --git a/sys/dev/sound/pcm/mixer.c b/sys/dev/sound/pcm/mixer.c
index 7ccb57c205ba..be4447b13964 100644
--- a/sys/dev/sound/pcm/mixer.c
+++ b/sys/dev/sound/pcm/mixer.c
@@ -1033,113 +1033,6 @@ mixer_close(struct cdev *i_dev, int flags, int mode, struct thread *td)
 }
 
 static int
-mixer_ioctl_channel(struct cdev *dev, u_long cmd, caddr_t arg, int mode,
-    struct thread *td, int from)
-{
-	struct snddev_info *d;
-	struct snd_mixer *m;
-	struct pcm_channel *c, *rdch, *wrch;
-	pid_t pid;
-	int j, ret;
-
-	if (td == NULL || td->td_proc == NULL)
-		return (-1);
-
-	m = dev->si_drv1;
-	d = device_get_softc(m->dev);
-	j = cmd & 0xff;
-
-	switch (j) {
-	case SOUND_MIXER_PCM:
-	case SOUND_MIXER_RECLEV:
-	case SOUND_MIXER_DEVMASK:
-	case SOUND_MIXER_CAPS:
-	case SOUND_MIXER_STEREODEVS:
-		break;
-	default:
-		return (-1);
-	}
-
-	pid = td->td_proc->p_pid;
-	rdch = NULL;
-	wrch = NULL;
-	c = NULL;
-	ret = -1;
-
-	/*
-	 * This is unfair. Imagine single proc opening multiple
-	 * instances of same direction. What we do right now
-	 * is looking for the first matching proc/pid, and just
-	 * that. Nothing more. Consider it done.
-	 *
-	 * The better approach of controlling specific channel
-	 * pcm or rec volume is by doing mixer ioctl
-	 * (SNDCTL_DSP_[SET|GET][PLAY|REC]VOL / SOUND_MIXER_[PCM|RECLEV]
-	 * on its open fd, rather than cracky mixer bypassing here.
-	 */
-	CHN_FOREACH(c, d, channels.pcm.opened) {
-		CHN_LOCK(c);
-		if (c->pid != pid ||
-		    !(c->feederflags & (1 << FEEDER_VOLUME))) {
-			CHN_UNLOCK(c);
-			continue;
-		}
-		if (rdch == NULL && c->direction == PCMDIR_REC) {
-			rdch = c;
-			if (j == SOUND_MIXER_RECLEV)
-				goto mixer_ioctl_channel_proc;
-		} else if (wrch == NULL && c->direction == PCMDIR_PLAY) {
-			wrch = c;
-			if (j == SOUND_MIXER_PCM)
-				goto mixer_ioctl_channel_proc;
-		}
-		CHN_UNLOCK(c);
-		if (rdch != NULL && wrch != NULL)
-			break;
-	}
-
-	if (rdch == NULL && wrch == NULL)
-		return (-1);
-
-	if ((j == SOUND_MIXER_DEVMASK || j == SOUND_MIXER_CAPS ||
-	    j == SOUND_MIXER_STEREODEVS) &&
-	    (cmd & ~0xff) == MIXER_READ(0)) {
-		mtx_lock(&m->lock);
-		*(int *)arg = mix_getdevs(m);
-		mtx_unlock(&m->lock);
-		if (rdch != NULL)
-			*(int *)arg |= SOUND_MASK_RECLEV;
-		if (wrch != NULL)
-			*(int *)arg |= SOUND_MASK_PCM;
-		ret = 0;
-	}
-
-	return (ret);
-
-mixer_ioctl_channel_proc:
-
-	KASSERT(c != NULL, ("%s(): NULL channel", __func__));
-	CHN_LOCKASSERT(c);
-
-	if ((cmd & ~0xff) == MIXER_WRITE(0)) {
-		int left, right, center;
-
-		left = *(int *)arg & 0x7f;
-		right = (*(int *)arg >> 8) & 0x7f;
-		center = (left + right) >> 1;
-		chn_setvolume_multi(c, SND_VOL_C_PCM, left, right, center);
-	} else if ((cmd & ~0xff) == MIXER_READ(0)) {
-		*(int *)arg = chn_getvolume_matrix(c, SND_VOL_C_PCM, SND_CHN_T_FL);
-		*(int *)arg |=
-		    chn_getvolume_matrix(c, SND_VOL_C_PCM, SND_CHN_T_FR) << 8;
-	}
-
-	CHN_UNLOCK(c);
-
-	return (0);
-}
-
-static int
 mixer_ioctl(struct cdev *i_dev, u_long cmd, caddr_t arg, int mode,
     struct thread *td)
 {
@@ -1156,15 +1049,7 @@ mixer_ioctl(struct cdev *i_dev, u_long cmd, caddr_t arg, int mode,
 	PCM_GIANT_ENTER(d);
 	PCM_ACQUIRE_QUICK(d);
 
-	ret = -1;
-
-	if (mixer_bypass != 0 && (d->flags & SD_F_VPC))
-		ret = mixer_ioctl_channel(i_dev, cmd, arg, mode, td,
-		    MIXER_CMD_CDEV);
-
-	if (ret == -1)
-		ret = mixer_ioctl_cmd(i_dev, cmd, arg, mode, td,
-		    MIXER_CMD_CDEV);
+	ret = mixer_ioctl_cmd(i_dev, cmd, arg, mode, td, MIXER_CMD_CDEV);
 
 	PCM_RELEASE_QUICK(d);
 	PCM_GIANT_LEAVE(d);