linux-kernel - [PATCH v10 20/41] ALSA: usb-audio: Check for support for requested audio format

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Message-ID: <20231215214955.12110-21-quic_wcheng@quicinc.com>
Date: Fri, 15 Dec 2023 13:49:34 -0800
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>,
        <gregkh@...uxfoundation.org>, <lgirdwood@...il.com>,
        <andersson@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
        <konrad.dybcio@...aro.org>, <Thinh.Nguyen@...opsys.com>,
        <broonie@...nel.org>, <bgoswami@...cinc.com>, <tiwai@...e.com>,
        <robh+dt@...nel.org>, <agross@...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 v10 20/41] 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 | 40 ++++++++++++++++++++++++++++++++++++++++
 sound/usb/card.h | 11 +++++++++++
 2 files changed, 51 insertions(+)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index c0b312e264bf..11b827b7a2a5 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -162,6 +162,46 @@ int snd_usb_unregister_platform_ops(void)
 }
 EXPORT_SYMBOL_GPL(snd_usb_unregister_platform_ops);
 
+/*
+ * 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;
+	const struct audioformat *fmt;
+
+	/*
+	 * Register mutex is held when populating and clearing usb_chip
+	 * array.
+	 */
+	mutex_lock(&register_mutex);
+	chip = usb_chip[card_idx];
+	if (!chip) {
+		mutex_unlock(&register_mutex);
+		return NULL;
+	}
+
+	if (enable[card_idx]) {
+		list_for_each_entry(as, &chip->pcm_list, list) {
+			subs = &as->substream[direction];
+			fmt = snd_usb_find_substream_format(subs, params);
+			if (fmt) {
+				mutex_unlock(&register_mutex);
+				return as;
+			}
+		}
+	}
+	mutex_unlock(&register_mutex);
+
+	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 02e4ea898db5..ed4a664e24e5 100644
--- a/sound/usb/card.h
+++ b/sound/usb/card.h
@@ -217,4 +217,15 @@ struct snd_usb_platform_ops {
 
 int snd_usb_register_platform_ops(struct snd_usb_platform_ops *ops);
 int snd_usb_unregister_platform_ops(void);
+
+#if IS_ENABLED(CONFIG_SND_USB_AUDIO)
+struct snd_usb_stream *snd_usb_find_suppported_substream(int card_idx,
+			struct snd_pcm_hw_params *params, int direction);
+#else
+static struct snd_usb_stream *snd_usb_find_suppported_substream(int card_idx,
+			struct snd_pcm_hw_params *params, int direction)
+{
+	return NULL;
+}
+#endif /* IS_ENABLED(CONFIG_SND_USB_AUDIO) */
 #endif /* __USBAUDIO_CARD_H */