ALSA: usb-audio: Check for support for requested audio format

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>
Acked-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20250409194804.3773260-10-quic_wcheng@quicinc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/sound/usb/card.c b/sound/usb/card.c
index a0087bde684c1289c52c9e909f522745e8eaf5cf..6c5b0e02e57b0263ab0873f10321e762d001c38b 100644 (file)
--- 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 6ec95b2edf863e252fc7c3422bc274a7a0c9b564..4f4f3f39b7fa446c8f5a57f05fb7248d4250bdda 100644 (file)
--- 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 */