[alsa-devel] [PATCH 2/3] ALSA: snd-usb: handle raw data format of UAC2 devices

[Daniel Mack]

UAC2 compliant audio devices may announce the capability to transport
raw audio data on their endpoints. Catch this and handle it as
'special' stream on the ALSA side.

Signed-off-by: Daniel Mack <zonque at gmail.com>
Reported-by: Andreas Koch <andreas at akdesigninc.com>
---
 include/linux/usb/audio-v2.h |    2 ++
 sound/usb/format.c           |   11 +++++++----
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/include/linux/usb/audio-v2.h b/include/linux/usb/audio-v2.h
index ed13053..c5f2158 100644
--- a/include/linux/usb/audio-v2.h
+++ b/include/linux/usb/audio-v2.h
@@ -170,6 +170,8 @@ struct uac2_as_header_descriptor {
 	__u8 iChannelNames;
 } __attribute__((packed));
 
+#define UAC2_FORMAT_TYPE_I_RAW_DATA	(1 << 31)
+
 /* 4.10.1.2 Class-Specific AS Isochronous Audio Data Endpoint Descriptor */
 
 struct uac2_iso_endpoint_descriptor {
diff --git a/sound/usb/format.c b/sound/usb/format.c
index b30d6fb..a695caf 100644
--- a/sound/usb/format.c
+++ b/sound/usb/format.c
@@ -47,7 +47,7 @@ static u64 parse_audio_format_i_type(struct snd_usb_audio *chip,
 				     int protocol)
 {
 	int sample_width, sample_bytes;
-	u64 pcm_formats;
+	u64 pcm_formats = 0;
 
 	switch (protocol) {
 	case UAC_VERSION_1:
@@ -63,14 +63,17 @@ static u64 parse_audio_format_i_type(struct snd_usb_audio *chip,
 		struct uac_format_type_i_ext_descriptor *fmt = _fmt;
 		sample_width = fmt->bBitResolution;
 		sample_bytes = fmt->bSubslotSize;
+
+		if (format & UAC2_FORMAT_TYPE_I_RAW_DATA)
+			pcm_formats |= SNDRV_PCM_FMTBIT_SPECIAL;
+
 		format <<= 1;
 		break;
 	}
 	}
 
-	pcm_formats = 0;
-
-	if (format == 0 || format == (1 << UAC_FORMAT_TYPE_I_UNDEFINED)) {
+	if ((pcm_formats == 0) &&
+	    (format == 0 || format == (1 << UAC_FORMAT_TYPE_I_UNDEFINED))) {
 		/* some devices don't define this correctly... */
 		snd_printdd(KERN_INFO "%d:%u:%d : format type 0 is detected, processed as PCM\n",
 			    chip->dev->devnum, fp->iface, fp->altsetting);
-- 
1.7.10.4