[PATCH v32 10/32] ALSA: usb-audio: Check for support for requested audio format

Wesley Cheng
2025-01-08T01:22:47Z

Allow for checks on a specific USB audio device to see if a requested PCM
format is supported. This is needed for support when playback is
initiated by the ASoC USB backend path.

Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
---
sound/usb/card.c | 32 ++++++++++++++++++++++++++++++++
sound/usb/card.h | 3 +++
2 files changed, 35 insertions(+)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index a0087bde684c..6c5b0e02e57b 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -119,6 +119,38 @@ static DEFINE_MUTEX(register_mutex);
static struct snd_usb_audio *usb_chip[SNDRV_CARDS];
static struct usb_driver usb_audio_driver;

+/*
+ * Checks to see if requested audio profile, i.e sample rate, # of
+ * channels, etc... is supported by the substream associated to the
+ * USB audio device.
+ */
+struct snd_usb_stream *
+snd_usb_find_suppported_substream(int card_idx, struct snd_pcm_hw_params *params,
+ int direction)
+{
+ struct snd_usb_audio *chip;
+ struct snd_usb_substream *subs;
+ struct snd_usb_stream *as;
+
+ /*
+ * Register mutex is held when populating and clearing usb_chip
+ * array.
+ */
+ guard(mutex)(&register_mutex);
+ chip = usb_chip[card_idx];
+
+ if (chip && enable[card_idx]) {
+ list_for_each_entry(as, &chip->pcm_list, list) {
+ subs = &as->substream[direction];
+ if (snd_usb_find_substream_format(subs, params))
+ return as;
+ }
+ }
+
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(snd_usb_find_suppported_substream);
+
/*
* disconnect streams
* called from usb_audio_disconnect()
diff --git a/sound/usb/card.h b/sound/usb/card.h
index 6ec95b2edf86..4f4f3f39b7fa 100644
--- a/sound/usb/card.h
+++ b/sound/usb/card.h
@@ -207,4 +207,7 @@ struct snd_usb_stream {
struct list_head list;
};

+struct snd_usb_stream *
+snd_usb_find_suppported_substream(int card_idx, struct snd_pcm_hw_params *params,
+ int direction);
#endif /* __USBAUDIO_CARD_H */