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>

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

sound/usb/usbaudio.c

@@ -71,6 +71,7 @@ static int pid[SNDRV_CARDS] = { [0 ... (SNDRV_CARDS-1)] = -1 };
 static int nrpacks = 8;		/* max. number of packets per urb */
 static int async_unlink = 1;
 static int device_setup[SNDRV_CARDS]; /* device parameter for this card*/
+static int ignore_ctl_error;
 
 module_param_array(index, int, NULL, 0444);
 MODULE_PARM_DESC(index, "Index value for the USB audio adapter.");
@@ -88,7 +89,9 @@ module_param(async_unlink, bool, 0444);
 MODULE_PARM_DESC(async_unlink, "Use async unlink mode.");
 module_param_array(device_setup, int, NULL, 0444);
 MODULE_PARM_DESC(device_setup, "Specific device setup (if needed).");
-
+module_param(ignore_ctl_error, bool, 0444);
+MODULE_PARM_DESC(ignore_ctl_error,
+		 "Ignore errors from USB controller for mixer interfaces.");
 
 /*
  * debug the h/w constraints
@@ -3633,7 +3636,7 @@ static void *snd_usb_audio_probe(struct usb_device *dev,
 	if (err > 0) {
 		/* create normal USB audio interfaces */
 		if (snd_usb_create_streams(chip, ifnum) < 0 ||
-		    snd_usb_create_mixer(chip, ifnum) < 0) {
+		    snd_usb_create_mixer(chip, ifnum, ignore_ctl_error) < 0) {
 			goto __error;
 		}
 	}

sound/usb/usbaudio.h

@@ -223,7 +223,8 @@ int snd_usb_ctl_msg(struct usb_device *dev, unsigned int pipe,
 		    __u8 request, __u8 requesttype, __u16 value, __u16 index,
 		    void *data, __u16 size, int timeout);
 
-int snd_usb_create_mixer(struct snd_usb_audio *chip, int ctrlif);
+int snd_usb_create_mixer(struct snd_usb_audio *chip, int ctrlif,
+			 int ignore_error);
 void snd_usb_mixer_disconnect(struct list_head *p);
 
 int snd_usb_create_midi_interface(struct snd_usb_audio *chip, struct usb_interface *iface,

sound/usb/usbmixer.c

@@ -2014,7 +2014,8 @@ static void snd_audigy2nx_proc_read(struct snd_info_entry *entry,
 	}
 }
 
-int snd_usb_create_mixer(struct snd_usb_audio *chip, int ctrlif)
+int snd_usb_create_mixer(struct snd_usb_audio *chip, int ctrlif,
+			 int ignore_error)
 {
 	static struct snd_device_ops dev_ops = {
 		.dev_free = snd_usb_mixer_dev_free
@@ -2029,9 +2030,7 @@ int snd_usb_create_mixer(struct snd_usb_audio *chip, int ctrlif)
 		return -ENOMEM;
 	mixer->chip = chip;
 	mixer->ctrlif = ctrlif;
-#ifdef IGNORE_CTL_ERROR
-	mixer->ignore_ctl_error = 1;
-#endif
+	mixer->ignore_ctl_error = ignore_error;
 	mixer->id_elems = kcalloc(256, sizeof(*mixer->id_elems), GFP_KERNEL);
 	if (!mixer->id_elems) {
 		kfree(mixer);