bcm2835: access controls under the audio mutex

I don't think the ALSA framework provides any kind of automatic
synchronization within the control callbacks. We most likely need
to ensure this manually, so add locking around all access to shared
mutable data. In particular, bcm2835_audio_set_ctls() should
probably always be called under our own audio lock.

sound/arm/bcm2835-ctl.c

@@ -94,6 +94,9 @@ static int snd_bcm2835_ctl_get(struct snd_kcontrol *kcontrol,
 {
 	struct bcm2835_chip *chip = snd_kcontrol_chip(kcontrol);
 
+	if (mutex_lock_interruptible(&chip->audio_mutex))
+		return -EINTR;
+
 	BUG_ON(!chip && !(chip->avail_substreams & AVAIL_SUBSTREAMS_MASK));
 
 	if (kcontrol->private_value == PCM_PLAYBACK_VOLUME)
@@ -103,6 +106,7 @@ static int snd_bcm2835_ctl_get(struct snd_kcontrol *kcontrol,
 	else if (kcontrol->private_value == PCM_PLAYBACK_DEVICE)
 		ucontrol->value.integer.value[0] = chip->dest;
 
+	mutex_unlock(&chip->audio_mutex);
 	return 0;
 }
 
@@ -112,11 +116,15 @@ static int snd_bcm2835_ctl_put(struct snd_kcontrol *kcontrol,
 	struct bcm2835_chip *chip = snd_kcontrol_chip(kcontrol);
 	int changed = 0;
 
+	if (mutex_lock_interruptible(&chip->audio_mutex))
+		return -EINTR;
+
 	if (kcontrol->private_value == PCM_PLAYBACK_VOLUME) {
 		audio_info("Volume change attempted.. volume = %d new_volume = %d\n", chip->volume, (int)ucontrol->value.integer.value[0]);
 		if (chip->mute == CTRL_VOL_MUTE) {
 			/* changed = toggle_mute(chip, CTRL_VOL_UNMUTE); */
-			return 1; /* should return 0 to signify no change but the mixer takes this as the opposite sign (no idea why) */
+			changed = 1; /* should return 0 to signify no change but the mixer takes this as the opposite sign (no idea why) */
+			goto unlock;
 		}
 		if (changed
 		    || (ucontrol->value.integer.value[0] != chip2alsa(chip->volume))) {
@@ -142,6 +150,8 @@ static int snd_bcm2835_ctl_put(struct snd_kcontrol *kcontrol,
 			printk(KERN_ERR "Failed to set ALSA controls..\n");
 	}
 
+unlock:
+	mutex_unlock(&chip->audio_mutex);
 	return changed;
 }
 
@@ -198,10 +208,14 @@ static int snd_bcm2835_spdif_default_get(struct snd_kcontrol *kcontrol,
 	struct bcm2835_chip *chip = snd_kcontrol_chip(kcontrol);
 	int i;
 
+	if (mutex_lock_interruptible(&chip->audio_mutex))
+		return -EINTR;
+
 	for (i = 0; i < 4; i++)
 		ucontrol->value.iec958.status[i] =
 			(chip->spdif_status >> (i * 8)) && 0xff;
 
+	mutex_unlock(&chip->audio_mutex);
 	return 0;
 }
 
@@ -212,12 +226,16 @@ static int snd_bcm2835_spdif_default_put(struct snd_kcontrol *kcontrol,
 	unsigned int val = 0;
 	int i, change;
 
+	if (mutex_lock_interruptible(&chip->audio_mutex))
+		return -EINTR;
+
 	for (i = 0; i < 4; i++)
 		val |= (unsigned int)ucontrol->value.iec958.status[i] << (i * 8);
 
 	change = val != chip->spdif_status;
 	chip->spdif_status = val;
 
+	mutex_unlock(&chip->audio_mutex);
 	return change;
 }
 
@@ -253,9 +271,14 @@ static int snd_bcm2835_spdif_stream_get(struct snd_kcontrol *kcontrol,
 	struct bcm2835_chip *chip = snd_kcontrol_chip(kcontrol);
 	int i;
 
+	if (mutex_lock_interruptible(&chip->audio_mutex))
+		return -EINTR;
+
 	for (i = 0; i < 4; i++)
 		ucontrol->value.iec958.status[i] =
 			(chip->spdif_status >> (i * 8)) & 0xff;
+
+	mutex_unlock(&chip->audio_mutex);
 	return 0;
 }
 
@@ -266,11 +289,15 @@ static int snd_bcm2835_spdif_stream_put(struct snd_kcontrol *kcontrol,
 	unsigned int val = 0;
 	int i, change;
 
+	if (mutex_lock_interruptible(&chip->audio_mutex))
+		return -EINTR;
+
 	for (i = 0; i < 4; i++)
 		val |= (unsigned int)ucontrol->value.iec958.status[i] << (i * 8);
 	change = val != chip->spdif_status;
 	chip->spdif_status = val;
 
+	mutex_unlock(&chip->audio_mutex);
 	return change;
 }
 
@@ -454,11 +481,17 @@ static int snd_bcm2835_chmap_ctl_get(struct snd_kcontrol *kcontrol,
 	unsigned int idx = snd_ctl_get_ioffidx(kcontrol, &ucontrol->id);
 	struct snd_pcm_substream *substream = snd_pcm_chmap_substream(info, idx);
 	struct cea_channel_speaker_allocation *ch = NULL;
+	int res = 0;
 	int cur = 0;
 	int i;
 
-	if (!substream || !substream->runtime)
+	if (mutex_lock_interruptible(&chip->audio_mutex))
-		return -ENODEV;
+		return -EINTR;
+
+	if (!substream || !substream->runtime) {
+		res = -ENODEV;
+		goto unlock;
+	}
 
 	for (i = 0; i < ARRAY_SIZE(channel_allocations); i++) {
 		if (channel_allocations[i].ca_index == chip->cea_chmap)
@@ -476,7 +509,10 @@ static int snd_bcm2835_chmap_ctl_get(struct snd_kcontrol *kcontrol,
 	}
 	while (cur < 8)
 		ucontrol->value.integer.value[cur++] = SNDRV_CHMAP_NA;
-	return 0;
+
+unlock:
+	mutex_unlock(&chip->audio_mutex);
+	return res;
 }
 
 static int snd_bcm2835_chmap_ctl_put(struct snd_kcontrol *kcontrol,
@@ -487,10 +523,16 @@ static int snd_bcm2835_chmap_ctl_put(struct snd_kcontrol *kcontrol,
 	unsigned int idx = snd_ctl_get_ioffidx(kcontrol, &ucontrol->id);
 	struct snd_pcm_substream *substream = snd_pcm_chmap_substream(info, idx);
 	int i, prepared = 0, cea_chmap = -1;
+	int res = 0;
 	int remap[8];
 
-	if (!substream || !substream->runtime)
+	if (mutex_lock_interruptible(&chip->audio_mutex))
-		return -ENODEV;
+		return -EINTR;
+
+	if (!substream || !substream->runtime) {
+		res = -ENODEV;
+		goto unlock;
+	}
 
 	switch (substream->runtime->status->state) {
 	case SNDRV_PCM_STATE_OPEN:
@@ -500,7 +542,8 @@ static int snd_bcm2835_chmap_ctl_put(struct snd_kcontrol *kcontrol,
 		prepared = 1;
 		break;
 	default:
-		return -EBUSY;
+		res = -EBUSY;
+		goto unlock;
 	}
 
 	for (i = 0; i < ARRAY_SIZE(channel_allocations); i++) {
@@ -538,19 +581,26 @@ static int snd_bcm2835_chmap_ctl_put(struct snd_kcontrol *kcontrol,
 		}
 	}
 
-	if (cea_chmap < 0)
+	if (cea_chmap < 0) {
-		return -EINVAL;
+		res = -EINVAL;
+		goto unlock;
+	}
 
 	/* don't change the layout if another substream is active */
-	if (chip->opened != (1 << substream->number) && chip->cea_chmap != cea_chmap)
+	if (chip->opened != (1 << substream->number) && chip->cea_chmap != cea_chmap) {
-		return -EBUSY; /* unsure whether this is a good error code */
+		res = -EBUSY; /* unsure whether this is a good error code */
+		goto unlock;
+	}
 
 	chip->cea_chmap = cea_chmap;
 	for (i = 0; i < 8; i++)
 		chip->map_channels[i] = remap[i];
 	if (prepared)
 		snd_bcm2835_pcm_prepare_again(substream);
-	return 0;
+
+unlock:
+	mutex_unlock(&chip->audio_mutex);
+	return res;
 }
 
 static int snd_bcm2835_add_chmap_ctl(bcm2835_chip_t * chip)

sound/arm/bcm2835-pcm.c

@@ -379,6 +379,9 @@ static int snd_bcm2835_pcm_prepare(struct snd_pcm_substream *substream)
 
 	audio_info(" .. IN\n");
 
+	if (mutex_lock_interruptible(&chip->audio_mutex))
+		return -EINTR;
+
 	snd_bcm2835_pcm_prepare_again(substream);
 
 	bcm2835_audio_setup(alsa_stream);
@@ -401,6 +404,7 @@ static int snd_bcm2835_pcm_prepare(struct snd_pcm_substream *substream)
 		      alsa_stream->buffer_size, alsa_stream->period_size,
 		      alsa_stream->pos, runtime->frame_bits);
 
+	mutex_unlock(&chip->audio_mutex);
 	audio_info(" .. OUT\n");
 	return 0;
 }