alsa: optimistically try resuming from suspend

Apparently snd_pcm_hw_params_can_resume() can return false even
though my hardware does in fact support resuming.  So stop
carrying that value in the canResume flag and just try to resume
when we're in the suspended state; falling back to
snd_pcm_prepare only if resuming fails.  libao does something
similar on resume, too.

While we're at it, use the E() macro which will enable us to
have better error reporting.

1 files changed, 12 insertions, 11 deletions

diff --git a/src/audioOutputs/audioOutput_alsa.c b/src/audioOutputs/audioOutput_alsa.c
index 890049779..932f2dbc0 100644
--- a/src/audioOutputs/audioOutput_alsa.c
+++ b/src/audioOutputs/audioOutput_alsa.c
@@ -61,7 +61,6 @@ typedef struct _AlsaData {
 	int sampleSize;
 	int useMmap;
 	int canPause;
-	int canResume;
 } AlsaData;
 
 static AlsaData *newAlsaData(void)
@@ -260,7 +259,6 @@ configure_hw:
 		goto error;
 
 	ad->canPause = snd_pcm_hw_params_can_pause(hwparams);
-	ad->canResume = snd_pcm_hw_params_can_resume(hwparams);
 
 	/* configure SW params */
 	snd_pcm_sw_params_alloca(&swparams);
@@ -307,7 +305,8 @@ fail:
 
 static int alsa_errorRecovery(AlsaData * ad, int err)
 {
-	snd_pcm_state_t state;
+	snd_pcm_state_t state = snd_pcm_state(ad->pcmHandle);
+	const char *err_cmd = NULL;
 
 	if (err == -EPIPE) {
 		DEBUG("Underrun on alsa device \"%s\"\n", ad->device);
@@ -315,18 +314,17 @@ static int alsa_errorRecovery(AlsaData * ad, int err)
 		DEBUG("alsa device \"%s\" was suspended\n", ad->device);
 	}
 
-	switch (state = snd_pcm_state(ad->pcmHandle)) {
+	switch (state) {
 	case SND_PCM_STATE_PAUSED:
-		err = snd_pcm_pause(ad->pcmHandle, /* disable */ 0);
+		err = E(snd_pcm_pause, ad->pcmHandle, /* disable */ 0);
 		break;
 	case SND_PCM_STATE_SUSPENDED:
-		err = ad->canResume ?
-		    snd_pcm_resume(ad->pcmHandle) :
-		    snd_pcm_prepare(ad->pcmHandle);
-		break;
+		if ((err = E(snd_pcm_resume, ad->pcmHandle)) == -EAGAIN)
+			return 0;
+		/* fall-through to snd_pcm_prepare: */
 	case SND_PCM_STATE_SETUP:
 	case SND_PCM_STATE_XRUN:
-		err = snd_pcm_prepare(ad->pcmHandle);
+		err = E(snd_pcm_prepare, ad->pcmHandle);
 		break;
 	case SND_PCM_STATE_DISCONNECTED:
 		/* so alsa_closeDevice won't try to drain: */
@@ -345,7 +343,10 @@ static int alsa_errorRecovery(AlsaData * ad, int err)
 		DEBUG("ALSA in unknown state: %s\n", snd_pcm_state_name(state));
 		break;
 	}
-
+error:
+	if (err && err_cmd)
+		ERROR("ALSA error on device \"%s\" (%s): %s\n",
+		      ad->device, err_cmd, snd_strerror(-err));
 	return err;
 }