[PATCH 3.2 121/200] ALSA: usb-audio: work around KEF X300A firmware bug

[Ben Hutchings]

3.2.56-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Clemens Ladisch <clemens@xxxxxxxxxx>

commit 624aef494f86ed0c58056361c06347ad62b26806 upstream.

When the driver tries to access Function Unit 10, the KEF X300A
speakers' firmware apparently locks up, making even PCM streaming
impossible.  Work around this by ignoring this FU.

Signed-off-by: Clemens Ladisch <clemens@xxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 sound/usb/mixer_maps.c | 9 +++++++++
 1 file changed, 9 insertions(+)

--- a/sound/usb/mixer_maps.c
+++ b/sound/usb/mixer_maps.c
@@ -304,6 +304,11 @@ static struct usbmix_name_map hercules_u
 	{ 0 }				/* terminator */
 };
 
+static const struct usbmix_name_map kef_x300a_map[] = {
+	{ 10, NULL }, /* firmware locks up (?) when we try to access this FU */
+	{ 0 }
+};
+
 /*
  * Control map entries
  */
@@ -371,6 +376,10 @@ static struct usbmix_ctl_map usbmix_ctl_
 		.map = scratch_live_map,
 		.ignore_ctl_error = 1,
 	},
+	{
+		.id = USB_ID(0x27ac, 0x1000),
+		.map = kef_x300a_map,
+	},
 	{ 0 } /* terminator */
 };
 

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