ALSA: pcm - Add proper state checks to snd_pcm_drain()

The handling for some PCM states is missing for snd_pcm_drain().
At least, XRUN streams should be simply dropped to SETUP, and a few
initial invalid states should be rejected.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/pcm_native.c

@@ -1360,7 +1360,14 @@ static int snd_pcm_prepare(struct snd_pcm_substream *substream,
 
 static int snd_pcm_pre_drain_init(struct snd_pcm_substream *substream, int state)
 {
-	substream->runtime->trigger_master = substream;
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	switch (runtime->status->state) {
+	case SNDRV_PCM_STATE_OPEN:
+	case SNDRV_PCM_STATE_DISCONNECTED:
+	case SNDRV_PCM_STATE_SUSPENDED:
+		return -EBADFD;
+	}
+	runtime->trigger_master = substream;
 	return 0;
 }
 
@@ -1379,6 +1386,9 @@ static int snd_pcm_do_drain_init(struct snd_pcm_substream *substream, int state)
 		case SNDRV_PCM_STATE_RUNNING:
 			runtime->status->state = SNDRV_PCM_STATE_DRAINING;
 			break;
+		case SNDRV_PCM_STATE_XRUN:
+			runtime->status->state = SNDRV_PCM_STATE_SETUP;
+			break;
 		default:
 			break;
 		}