audio: attempt to gracefully handle disconnected/reconnected devices

Currently only ALSA is supported/tested, and only if the mixer
device is not on the audio device being disconnected (software
mixer).

This patch allows me to disconnect my Headroom Total Airhead USB
sound card, and resume playback (skips to the next song, which
should be fixed) when the device is plugged back in.

git-svn-id: https://svn.musicpd.org/mpd/trunk@4364 09075e82-0dd4-0310-85a5-a0d7c8717e4f

2 files changed, 13 insertions, 5 deletions

diff --git a/src/audio.c b/src/audio.c
index 6766159b2..8180b290b 100644
--- a/src/audio.c
+++ b/src/audio.c
@@ -274,7 +274,7 @@ static void syncAudioDevicesEnabledArrays(void) {
 
 static int flushAudioBuffer() {
 	int ret = -1;
-	int i;
+	int i, err;
 
 	if(audioBufferPos == 0) return 0;
 
@@ -286,11 +286,14 @@ static int flushAudioBuffer() {
 
 	for(i = 0; i < audioOutputArraySize; i++) {
 		if(!myAudioDevicesEnabled[i]) continue;
-		if(0 == playAudioOutput(audioOutputArray[i], audioBuffer, 
-					audioBufferPos)) 
-		{
+		err = playAudioOutput(audioOutputArray[i], audioBuffer,
+							audioBufferPos);
+		if (!err)
 			ret = 0;
-		}
+		else if (err < 0)
+			/* device should already be closed if the play func
+			 * returned an error */
+			myAudioDevicesEnabled[i] = 0;
 	}
 
 	audioBufferPos = 0;
diff --git a/src/audioOutputs/audioOutput_alsa.c b/src/audioOutputs/audioOutput_alsa.c
index bc727c556..3abd81f31 100644
--- a/src/audioOutputs/audioOutput_alsa.c
+++ b/src/audioOutputs/audioOutput_alsa.c
@@ -315,6 +315,11 @@ static int alsa_errorRecovery(AlsaData * ad, int err) {
 	case SND_PCM_STATE_XRUN:
 		err = snd_pcm_prepare(ad->pcmHandle);
 		break;
+	case SND_PCM_STATE_DISCONNECTED:
+		/* so alsa_closeDevice won't try to drain: */
+		snd_pcm_close(ad->pcmHandle);
+		ad->pcmHandle = NULL;
+		break;
 	default:
 		/* unknown state, do nothing */
 		break;