[PATCH] ASoC: pcm: Do not open FEs with no BEs connected

[PATCH] ASoC: pcm: Do not open FEs with no BEs connected

[Cezary Rojewski]

The check is performed in prepare-step, that is dpcm_fe_dai_prepare()
but that is very late - code operates on invalid configuration from
dpcm_fe_dai_open() till it gets there. Relocate the check to the
open-step to avoid any invalid scenarios.

Reviewed-by: Amadeusz Sławiński <amadeuszx.slawinski@linux.intel.com>
Signed-off-by: Cezary Rojewski <cezary.rojewski@intel.com>
---
 sound/soc/soc-pcm.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index 43835197d1fe..2c21fd528afd 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -2510,17 +2510,6 @@ static int dpcm_fe_dai_prepare(struct snd_pcm_substream *substream)
 
 	dpcm_set_fe_update_state(fe, stream, SND_SOC_DPCM_UPDATE_FE);
 
-	/* there is no point preparing this FE if there are no BEs */
-	if (list_empty(&fe->dpcm[stream].be_clients)) {
-		/* dev_err_once() for visibility, dev_dbg() for debugging UCM profiles */
-		dev_err_once(fe->dev, "ASoC: no backend DAIs enabled for %s, possibly missing ALSA mixer-based routing or UCM profile\n",
-			     fe->dai_link->name);
-		dev_dbg(fe->dev, "ASoC: no backend DAIs enabled for %s\n",
-			fe->dai_link->name);
-		ret = -EINVAL;
-		goto out;
-	}
-
 	ret = dpcm_be_dai_prepare(fe, stream);
 	if (ret < 0)
 		goto out;
@@ -2776,11 +2765,23 @@ static int dpcm_fe_dai_open(struct snd_pcm_substream *fe_substream)
 	/* calculate valid and active FE <-> BE dpcms */
 	dpcm_add_paths(fe, stream, &list);
 
+	/* There is no point starting up this FE if there are no BEs. */
+	if (list_empty(&fe->dpcm[stream].be_clients)) {
+		/* dev_err_once() for visibility, dev_dbg() for debugging UCM profiles. */
+		dev_err_once(fe->dev, "ASoC: no backend DAIs enabled for %s, possibly missing ALSA mixer-based routing or UCM profile\n",
+			     fe->dai_link->name);
+		dev_dbg(fe->dev, "ASoC: no backend DAIs enabled for %s\n", fe->dai_link->name);
+
+		ret = -EINVAL;
+		goto put_path;
+	}
+
 	ret = dpcm_fe_dai_startup(fe_substream);
 	if (ret < 0)
 		dpcm_fe_dai_cleanup(fe_substream);
 
 	dpcm_clear_pending_state(fe, stream);
+put_path:
 	dpcm_path_put(&list);
 open_end:
 	snd_soc_dpcm_mutex_unlock(fe);
-- 
2.25.1

Re: [PATCH] ASoC: pcm: Do not open FEs with no BEs connected

[Mark Brown]

On Fri, 30 May 2025 16:12:31 +0200, Cezary Rojewski wrote:
> The check is performed in prepare-step, that is dpcm_fe_dai_prepare()
> but that is very late - code operates on invalid configuration from
> dpcm_fe_dai_open() till it gets there. Relocate the check to the
> open-step to avoid any invalid scenarios.
> 
> 

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-next

Thanks!

[1/1] ASoC: pcm: Do not open FEs with no BEs connected
      commit: 59a4d9a9efd921ae2b722ffa52217124bcbc0acf

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark