ALSA: usb-audio - Add ignore_ctl_error parameter

Added the ignore_ctl_error parameter to enable/disable the control-error
handling for mixer interfaces.  It was a hard-coded ifdef, and now you
can change it more easily.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

1 files changed, 5 insertions, 0 deletions

diff --git a/Documentation/sound/alsa/ALSA-Configuration.txt b/Documentation/sound/alsa/ALSA-Configuration.txt
index 68bbc25ff39e..b33e030509fb 100644
--- a/Documentation/sound/alsa/ALSA-Configuration.txt
+++ b/Documentation/sound/alsa/ALSA-Configuration.txt
@@ -1983,6 +1983,8 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed.
     device_setup    - Device specific magic number (optional)
                     - Influence depends on the device
                     - Default: 0x0000 
+    ignore_ctl_error - Ignore any USB-controller regarding mixer
+                       interface (default: no)
 
     This module supports multiple devices, autoprobe and hotplugging.
 
@@ -1991,6 +1993,9 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed.
         check.
     NB: async_unlink=0 would cause Oops.  It remains just for
         debugging purpose (if any).
+    NB: ignore_ctl_error=1 may help when you get an error at accessing
+        the mixer element such as URB error -22.  This happens on some
+        buggy USB device or the controller.
 
   Module snd-usb-caiaq
   --------------------