[PATCH] ALSA: pcm: Fix source frame count calculation

[PATCH] ALSA: pcm: Fix source frame count calculation

[Sreeraj S Kurup]

Pass the updated frame count to the "src_frames()" callback.

When the next plugin handles fewer frames than requested, use the
actual frame count instead of the original requested count.

This ensures the correct number of source frames is calculated.

Signed-off-by: Sreeraj S Kurup <sreekuttan2156239@gmail.com>
---
 sound/core/oss/pcm_plugin.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/core/oss/pcm_plugin.c b/sound/core/oss/pcm_plugin.c
index acf5ca663ba8..3de713779993 100644
--- a/sound/core/oss/pcm_plugin.c
+++ b/sound/core/oss/pcm_plugin.c
@@ -604,7 +604,7 @@ snd_pcm_sframes_t snd_pcm_plug_write_transfer(struct snd_pcm_substream *plug, st
 			if (err != frames1) {
 				frames = err;
 				if (plugin->src_frames) {
-					frames = plugin->src_frames(plugin, frames1);
+					frames = plugin->src_frames(plugin, err);
 					if (frames <= 0)
 						return frames;
 				}
-- 
2.55.0

Re: [PATCH] ALSA: pcm: Fix source frame count calculation

[Takashi Iwai]

On Mon, 02 Nov 2026 15:16:47 +0100,
Sreeraj S Kurup wrote:
> 
> Pass the updated frame count to the "src_frames()" callback.
> 
> When the next plugin handles fewer frames than requested, use the
> actual frame count instead of the original requested count.
> 
> This ensures the correct number of source frames is calculated.
> 
> Signed-off-by: Sreeraj S Kurup <sreekuttan2156239@gmail.com>
> ---
>  sound/core/oss/pcm_plugin.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/sound/core/oss/pcm_plugin.c b/sound/core/oss/pcm_plugin.c
> index acf5ca663ba8..3de713779993 100644
> --- a/sound/core/oss/pcm_plugin.c
> +++ b/sound/core/oss/pcm_plugin.c
> @@ -604,7 +604,7 @@ snd_pcm_sframes_t snd_pcm_plug_write_transfer(struct snd_pcm_substream *plug, st
>  			if (err != frames1) {
>  				frames = err;
>  				if (plugin->src_frames) {
> -					frames = plugin->src_frames(plugin, frames1);
> +					frames = plugin->src_frames(plugin, err);

Hm, do you really see actually hitting this code path?
As far as I see, the all client_channels() callbacks return the frame
back as given, so the condition (err != frames1) would be always
false.


Takashi

Re: [PATCH] ALSA: pcm: Fix source frame count calculation

[Sreeraj S Kurup]

You're right. I checked the callback implementation, and 
"snd_pcm_plugin_client_channels()" always returns the input 
frame count. All plugins created through "snd_pcm_plugin_build()" 
use this callback.

So the condition "err != frames1" is not reached in the normal path. 
My patch is unnecessary. Sorry for the noise.

Re: [PATCH] ALSA: pcm: Fix source frame count calculation

[Takashi Iwai]

On Mon, 02 Nov 2026 15:47:36 +0100,
Sreeraj S Kurup wrote:
> 
> You're right. I checked the callback implementation, and 
> "snd_pcm_plugin_client_channels()" always returns the input 
> frame count. All plugins created through "snd_pcm_plugin_build()" 
> use this callback.
> 
> So the condition "err != frames1" is not reached in the normal path. 
> My patch is unnecessary. Sorry for the noise.

Well, the logic you described looks still correct, so it's better to
correct the code even if it's only hypothetical.

So I applied your patch now with a bit more explanation.


thanks,

Takashi

Re: [PATCH] ALSA: pcm: Fix source frame count calculation

[Sreeraj S Kurup]

Hi,

Thanks for reviewing and applying the patch, and for adding the extra explanation.

Best regards,
Sreeraj

[PATCH] ALSA: pcm: Fix source frame count calculation

[Sreeraj S Kurup]

Pass the updated frame count to the "src_frames()" callback.

When the next plugin handles fewer frames than requested, use the
actual frame count instead of the original requested count.

This ensures the correct number of source frames is calculated.

Signed-off-by: Sreeraj S Kurup <sreekuttan2156239@gmail.com>
---
 sound/core/oss/pcm_plugin.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/core/oss/pcm_plugin.c b/sound/core/oss/pcm_plugin.c
index acf5ca663ba8..3de713779993 100644
--- a/sound/core/oss/pcm_plugin.c
+++ b/sound/core/oss/pcm_plugin.c
@@ -604,7 +604,7 @@ snd_pcm_sframes_t snd_pcm_plug_write_transfer(struct snd_pcm_substream *plug, st
 			if (err != frames1) {
 				frames = err;
 				if (plugin->src_frames) {
-					frames = plugin->src_frames(plugin, frames1);
+					frames = plugin->src_frames(plugin, err);
 					if (frames <= 0)
 						return frames;
 				}
-- 
2.55.0