[RFC PATCH 1/2] ALSA: pcm: allow capture reads while draining

[Joonho Lee <mynameisjune111@gmail.com>]

Allow capture transfer calls in DRAINING so already captured tail frames
remain readable until drain completes.

Assisted-by: LLM
Signed-off-by: Joonho Lee <mynameisjune111@gmail.com>
---
 sound/core/pcm_lib.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index 4d665b4148d7..de952f639d3b 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -2208,13 +2208,17 @@ static int pcm_sanity_check(struct snd_pcm_substream *substream)
 	return 0;
 }
 
-static int pcm_accessible_state(struct snd_pcm_runtime *runtime)
+static int pcm_accessible_state(struct snd_pcm_substream *substream)
 {
+	struct snd_pcm_runtime *runtime = substream->runtime;
+
 	switch (runtime->state) {
 	case SNDRV_PCM_STATE_PREPARED:
 	case SNDRV_PCM_STATE_RUNNING:
 	case SNDRV_PCM_STATE_PAUSED:
 		return 0;
+	case SNDRV_PCM_STATE_DRAINING:
+		return substream->stream == SNDRV_PCM_STREAM_CAPTURE ? 0 : -EBADFD;
 	case SNDRV_PCM_STATE_XRUN:
 		return -EPIPE;
 	case SNDRV_PCM_STATE_SUSPENDED:
@@ -2320,7 +2324,7 @@ snd_pcm_sframes_t __snd_pcm_lib_xfer(struct snd_pcm_substream *substream,
 	nonblock = !!(substream->f_flags & O_NONBLOCK);
 
 	snd_pcm_stream_lock_irq(substream);
-	err = pcm_accessible_state(runtime);
+	err = pcm_accessible_state(substream);
 	if (err < 0)
 		goto _end_unlock;
 
@@ -2388,7 +2392,7 @@ snd_pcm_sframes_t __snd_pcm_lib_xfer(struct snd_pcm_substream *substream,
 		atomic_dec(&runtime->buffer_accessing);
 		if (err < 0)
 			goto _end_unlock;
-		err = pcm_accessible_state(runtime);
+		err = pcm_accessible_state(substream);
 		if (err < 0)
 			goto _end_unlock;
 		appl_ptr += frames;