[PATCH v22 20/38] ASoC: usb: Add PCM format check API for USB backend

[Wesley Cheng]

Introduce a helper to check if a particular PCM format is supported by the
USB audio device connected.  If the USB audio device does not have an
audio profile which can support the requested format, then notify the USB
backend.

Signed-off-by: Wesley Cheng <quic_wcheng@xxxxxxxxxxx>
---
 include/sound/soc-usb.h |  9 +++++++++
 sound/soc/soc-usb.c     | 25 +++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/include/sound/soc-usb.h b/include/sound/soc-usb.h
index e8fe4439c234..4b1b992c8b27 100644
--- a/include/sound/soc-usb.h
+++ b/include/sound/soc-usb.h
@@ -39,6 +39,8 @@ struct snd_soc_usb {
 
 #if IS_ENABLED(CONFIG_SND_SOC_USB)
 const char *snd_soc_usb_get_components_tag(bool playback);
+int snd_soc_usb_find_supported_format(int card_idx,
+				struct snd_pcm_hw_params *params, int direction);
 
 int snd_soc_usb_connect(struct device *usbdev, struct snd_soc_usb_device *sdev);
 int snd_soc_usb_disconnect(struct device *usbdev, struct snd_soc_usb_device *sdev);
@@ -55,6 +57,13 @@ static inline const char *snd_soc_usb_get_components_tag(bool playback)
 	return "";
 }
 
+static inline int snd_soc_usb_find_supported_format(int card_idx,
+					  struct snd_pcm_hw_params *params,
+					  int direction)
+{
+	return -EINVAL;
+}
+
 static inline int snd_soc_usb_connect(struct device *usbdev,
 					struct snd_soc_usb_device *sdev)
 {
diff --git a/sound/soc/soc-usb.c b/sound/soc/soc-usb.c
index 8490715791a5..3bb66808f196 100644
--- a/sound/soc/soc-usb.c
+++ b/sound/soc/soc-usb.c
@@ -74,6 +74,31 @@ void *snd_soc_usb_find_priv_data(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(snd_soc_usb_find_priv_data);
 
+/**
+ * snd_soc_usb_find_supported_format() - Check if audio format is supported
+ * @card_idx: USB sound chip array index
+ * @params: PCM parameters
+ * @direction: capture or playback
+ *
+ * Ensure that a requested audio profile from the ASoC side is able to be
+ * supported by the USB device.
+ *
+ * Return 0 on success, negative on error.
+ *
+ */
+int snd_soc_usb_find_supported_format(int card_idx,
+				struct snd_pcm_hw_params *params, int direction)
+{
+	struct snd_usb_stream *as;
+
+	as = snd_usb_find_suppported_substream(card_idx, params, direction);
+	if (!as)
+		return -EOPNOTSUPP;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_find_supported_format);
+
 /**
  * snd_soc_usb_allocate_port() - allocate a SOC USB device
  * @component: USB DPCM backend DAI component