ALSA: usb-audio: Rename and export mixer_vol_tlv

Rename mixer_vol_tlv to snd_usb_mixer_vol_tlv and export it to make
it reuseable in mixer_quirks.c.
Signed-off-by: NFelix Homann <linuxaudio@showlabor.de>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/usb/mixer.c

@@ -486,7 +486,7 @@ static int set_cur_mix_value(struct usb_mixer_elem_info *cval, int channel,
 /*
  * TLV callback for mixer volume controls
  */
-static int mixer_vol_tlv(struct snd_kcontrol *kcontrol, int op_flag,
+int snd_usb_mixer_vol_tlv(struct snd_kcontrol *kcontrol, int op_flag,
 			 unsigned int size, unsigned int __user *_tlv)
 {
 	struct usb_mixer_elem_info *cval = kcontrol->private_data;
@@ -1158,7 +1158,7 @@ static void build_feature_ctl(struct mixer_build *state, void *raw_desc,
 		if (control == UAC_FU_VOLUME) {
 			check_mapped_dB(map, cval);
 			if (cval->dBmin < cval->dBmax || !cval->initialized) {
-				kctl->tlv.c = mixer_vol_tlv;
+				kctl->tlv.c = snd_usb_mixer_vol_tlv;
 				kctl->vd[0].access |= 
 					SNDRV_CTL_ELEM_ACCESS_TLV_READ |
 					SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK;

sound/usb/mixer.h

@@ -68,4 +68,7 @@ int snd_usb_mixer_activate(struct usb_mixer_interface *mixer);
 int snd_usb_mixer_add_control(struct usb_mixer_interface *mixer,
 			      struct snd_kcontrol *kctl);
 
+int snd_usb_mixer_vol_tlv(struct snd_kcontrol *kcontrol, int op_flag,
+			  unsigned int size, unsigned int __user *_tlv);
+
 #endif /* __USBMIXER_H */