linux-kernel - [PATCH v29 12/33] ALSA: usb-audio: Check for support for requested audio format

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Message-ID: <20241015212915.1206789-13-quic_wcheng@quicinc.com>
Date: Tue, 15 Oct 2024 14:28:54 -0700
From: Wesley Cheng <quic_wcheng@...cinc.com>
To: <srinivas.kandagatla@...aro.org>, <mathias.nyman@...el.com>,
        <perex@...ex.cz>, <conor+dt@...nel.org>, <dmitry.torokhov@...il.com>,
        <corbet@....net>, <lgirdwood@...il.com>, <tiwai@...e.com>,
        <krzk+dt@...nel.org>, <pierre-louis.bossart@...ux.intel.com>,
        <Thinh.Nguyen@...opsys.com>, <broonie@...nel.org>,
        <bgoswami@...cinc.com>, <robh@...nel.org>,
        <gregkh@...uxfoundation.org>
CC: <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-sound@...r.kernel.org>, <linux-input@...r.kernel.org>,
        <linux-usb@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-doc@...r.kernel.org>, <alsa-devel@...a-project.org>,
        Wesley Cheng
	<quic_wcheng@...cinc.com>
Subject: [PATCH v29 12/33] 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@...ux.intel.com>
Signed-off-by: Wesley Cheng <quic_wcheng@...cinc.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 c6d9d8d548b4..1f9dfcd8f336 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 */