ALSA: usb-audio: add new quirk type QUIRK_AUDIO_STANDARD_MIXER

This quirk type will let the driver assume that there is a standard
mixer on a given interface, or that a specific mixer quirks will handle
the device.
Signed-off-by: Daniel Mack <zonque@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/quirks.c

@@ -263,6 +263,20 @@ static int create_uaxx_quirk(struct snd_usb_audio *chip,
 	return 0;
 }
 
+/*
+ * Create a standard mixer for the specified interface.
+ */
+static int create_standard_mixer_quirk(struct snd_usb_audio *chip,
+				       struct usb_interface *iface,
+				       struct usb_driver *driver,
+				       const struct snd_usb_audio_quirk *quirk)
+{
+	if (quirk->ifnum < 0)
+		return 0;
+
+	return snd_usb_create_mixer(chip, quirk->ifnum, 0);
+}
+
 /*
  * audio-interface quirks
  *
@@ -295,7 +309,8 @@ int snd_usb_create_quirk(struct snd_usb_audio *chip,
 		[QUIRK_AUDIO_STANDARD_INTERFACE] = create_standard_audio_quirk,
 		[QUIRK_AUDIO_FIXED_ENDPOINT] = create_fixed_stream_quirk,
 		[QUIRK_AUDIO_EDIROL_UAXX] = create_uaxx_quirk,
-		[QUIRK_AUDIO_ALIGN_TRANSFER] = create_align_transfer_quirk
+		[QUIRK_AUDIO_ALIGN_TRANSFER] = create_align_transfer_quirk,
+		[QUIRK_AUDIO_STANDARD_MIXER] = create_standard_mixer_quirk,
 	};
 
 	if (quirk->type < QUIRK_TYPE_COUNT) {

sound/usb/usbaudio.h

@@ -84,6 +84,7 @@ enum quirk_type {
 	QUIRK_AUDIO_FIXED_ENDPOINT,
 	QUIRK_AUDIO_EDIROL_UAXX,
 	QUIRK_AUDIO_ALIGN_TRANSFER,
+	QUIRK_AUDIO_STANDARD_MIXER,
 
 	QUIRK_TYPE_COUNT
 };