linux-kernel - [PATCH v24 32/34] ALSA: usb-audio: Check for support for requested audio format

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Message-ID: <20240801011730.4797-33-quic_wcheng@quicinc.com>
Date: Wed, 31 Jul 2024 18:17:28 -0700
From: Wesley Cheng <quic_wcheng@...cinc.com>
To: <srinivas.kandagatla@...aro.org>, <mathias.nyman@...el.com>,
        <perex@...ex.cz>, <conor+dt@...nel.org>, <corbet@....net>,
        <broonie@...nel.org>, <lgirdwood@...il.com>, <krzk+dt@...nel.org>,
        <Thinh.Nguyen@...opsys.com>, <bgoswami@...cinc.com>, <tiwai@...e.com>,
        <gregkh@...uxfoundation.org>, <robh@...nel.org>
CC: <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-sound@...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 v24 32/34] 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.

Signed-off-by: Wesley Cheng <quic_wcheng@...cinc.com>
---
 sound/usb/card.c | 31 +++++++++++++++++++++++++++++++
 sound/usb/card.h |  2 ++
 2 files changed, 33 insertions(+)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 70b7f22ff495..8c22f6bfdef2 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -176,6 +176,37 @@ void snd_usb_rediscover_devices(void)
 }
 EXPORT_SYMBOL_GPL(snd_usb_rediscover_devices);
 
+/*
+ * 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 f0794aa06cd7..99d6a784eacf 100644
--- a/sound/usb/card.h
+++ b/sound/usb/card.h
@@ -220,4 +220,6 @@ int snd_usb_register_platform_ops(struct snd_usb_platform_ops *ops);
 int snd_usb_unregister_platform_ops(void);
 
 void snd_usb_rediscover_devices(void);
+struct snd_usb_stream *snd_usb_find_suppported_substream(int card_idx,
+				struct snd_pcm_hw_params *params, int direction);
 #endif /* __USBAUDIO_CARD_H */