ALSA: aloop: Support return of error code for timer start and stop

This is required for additional timer implementations which could detect
errors and want to throw them.
Signed-off-by: Timo Wischer <twischer@de.adit-jv.com>
Signed-off-by: Andrew Gabbasov <andrew_gabbasov@mentor.com>
Link: https://lore.kernel.org/r/20191120174955.6410-3-andrew_gabbasov@mentor.comSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/drivers/aloop.c

@@ -155,7 +155,7 @@ static inline unsigned int get_rate_shift(struct loopback_pcm *dpcm)
 }
 
 /* call in cable->lock */
-static void loopback_timer_start(struct loopback_pcm *dpcm)
+static int loopback_timer_start(struct loopback_pcm *dpcm)
 {
 	unsigned long tick;
 	unsigned int rate_shift = get_rate_shift(dpcm);
@@ -171,18 +171,24 @@ static void loopback_timer_start(struct loopback_pcm *dpcm)
 	tick = dpcm->period_size_frac - dpcm->irq_pos;
 	tick = (tick + dpcm->pcm_bps - 1) / dpcm->pcm_bps;
 	mod_timer(&dpcm->timer, jiffies + tick);
+
+	return 0;
 }
 
 /* call in cable->lock */
-static inline void loopback_timer_stop(struct loopback_pcm *dpcm)
+static inline int loopback_timer_stop(struct loopback_pcm *dpcm)
 {
 	del_timer(&dpcm->timer);
 	dpcm->timer.expires = 0;
+
+	return 0;
 }
 
-static inline void loopback_timer_stop_sync(struct loopback_pcm *dpcm)
+static inline int loopback_timer_stop_sync(struct loopback_pcm *dpcm)
 {
 	del_timer_sync(&dpcm->timer);
+
+	return 0;
 }
 
 #define CABLE_VALID_PLAYBACK	(1 << SNDRV_PCM_STREAM_PLAYBACK)
@@ -251,7 +257,7 @@ static int loopback_trigger(struct snd_pcm_substream *substream, int cmd)
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	struct loopback_pcm *dpcm = runtime->private_data;
 	struct loopback_cable *cable = dpcm->cable;
-	int err, stream = 1 << substream->stream;
+	int err = 0, stream = 1 << substream->stream;
 
 	switch (cmd) {
 	case SNDRV_PCM_TRIGGER_START:
@@ -264,7 +270,7 @@ static int loopback_trigger(struct snd_pcm_substream *substream, int cmd)
 		spin_lock(&cable->lock);	
 		cable->running |= stream;
 		cable->pause &= ~stream;
-		loopback_timer_start(dpcm);
+		err = loopback_timer_start(dpcm);
 		spin_unlock(&cable->lock);
 		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
 			loopback_active_notify(dpcm);
@@ -273,7 +279,7 @@ static int loopback_trigger(struct snd_pcm_substream *substream, int cmd)
 		spin_lock(&cable->lock);	
 		cable->running &= ~stream;
 		cable->pause &= ~stream;
-		loopback_timer_stop(dpcm);
+		err = loopback_timer_stop(dpcm);
 		spin_unlock(&cable->lock);
 		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
 			loopback_active_notify(dpcm);
@@ -282,7 +288,7 @@ static int loopback_trigger(struct snd_pcm_substream *substream, int cmd)
 	case SNDRV_PCM_TRIGGER_SUSPEND:
 		spin_lock(&cable->lock);	
 		cable->pause |= stream;
-		loopback_timer_stop(dpcm);
+		err = loopback_timer_stop(dpcm);
 		spin_unlock(&cable->lock);
 		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
 			loopback_active_notify(dpcm);
@@ -292,7 +298,7 @@ static int loopback_trigger(struct snd_pcm_substream *substream, int cmd)
 		spin_lock(&cable->lock);
 		dpcm->last_jiffies = jiffies;
 		cable->pause &= ~stream;
-		loopback_timer_start(dpcm);
+		err = loopback_timer_start(dpcm);
 		spin_unlock(&cable->lock);
 		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
 			loopback_active_notify(dpcm);
@@ -300,7 +306,7 @@ static int loopback_trigger(struct snd_pcm_substream *substream, int cmd)
 	default:
 		return -EINVAL;
 	}
-	return 0;
+	return err;
 }
 
 static void params_change(struct snd_pcm_substream *substream)
@@ -321,9 +327,11 @@ static int loopback_prepare(struct snd_pcm_substream *substream)
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	struct loopback_pcm *dpcm = runtime->private_data;
 	struct loopback_cable *cable = dpcm->cable;
-	int bps, salign;
+	int err, bps, salign;
 
-	loopback_timer_stop_sync(dpcm);
+	err = loopback_timer_stop_sync(dpcm);
+	if (err < 0)
+		return err;
 
 	salign = (snd_pcm_format_physical_width(runtime->format) *
 						runtime->channels) / 8;