[PATCH 6/6] ALSA: usb: Only get control header for UAC1 class.

[Jorge Sanjuan <jorge.sanjuan@codethink.co.uk>]

The control header needs to be read from buffer only in the case
of UAC1 protocol.

Signed-off-by: Jorge Sanjuan <jorge.sanjuan@codethink.co.uk>
---
 sound/usb/card.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index fa3cabd1cadc..646a0408f809 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -226,16 +226,9 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
 
 	/* find audiocontrol interface */
 	host_iface = &usb_ifnum_to_if(dev, ctrlif)->altsetting[0];
-	control_header = snd_usb_find_csint_desc(host_iface->extra,
-						 host_iface->extralen,
-						 NULL, UAC_HEADER);
 	altsd = get_iface_desc(host_iface);
 	protocol = altsd->bInterfaceProtocol;
 
-	if (!control_header) {
-		dev_err(&dev->dev, "cannot find UAC_HEADER\n");
-		return -EINVAL;
-	}
 
 	switch (protocol) {
 	default:
@@ -245,7 +238,17 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
 		/* fall through */
 
 	case UAC_VERSION_1: {
-		struct uac1_ac_header_descriptor *h1 = control_header;
+		struct uac1_ac_header_descriptor *h1;
+
+		control_header = snd_usb_find_csint_desc(host_iface->extra,
+							 host_iface->extralen,
+							 NULL, UAC_HEADER);
+		if (!control_header) {
+			dev_err(&dev->dev, "cannot find UAC_HEADER\n");
+			return -EINVAL;
+		}
+
+		h1 = control_header;
 
 		if (!h1->bInCollection) {
 			dev_info(&dev->dev, "skipping empty audio interface (v1)\n");
-- 
2.11.0