Commit 7bc5ba7e authored by Takashi Iwai's avatar Takashi Iwai Committed by Jaroslav Kysela
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[ALSA] Add TLV support to snd-usb-audio driver 



Added TLV-read support to snd-usb-audio driver for passing
the volume dB scale information to user-space.

Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
Signed-off-by: default avatarJaroslav Kysela <perex@suse.cz>
parent 6a65d793

sound/usb/usbmixer.c

+27 −0
Original line number Diff line number Diff line
@@ -37,6 +37,7 @@ 
#include <sound/control.h>

#include <sound/hwdep.h>

#include <sound/info.h>

#include <sound/tlv.h>



#include "usbaudio.h"
@@ -416,6 +417,26 @@ static inline int set_cur_mix_value(struct usb_mixer_elem_info *cval, int channe 
	return set_ctl_value(cval, SET_CUR, (cval->control << 8) | channel, value);

}



/*

 * TLV callback for mixer volume controls

 */

static int 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;

	DECLARE_TLV_DB_SCALE(scale, 0, 0, 0);



	if (size < sizeof(scale))

		return -ENOMEM;

	/* USB descriptions contain the dB scale in 1/256 dB unit

	 * while ALSA TLV contains in 1/100 dB unit

	 */

	scale[2] = (convert_signed_value(cval, cval->min) * 100) / 256;

	scale[3] = (convert_signed_value(cval, cval->res) * 100) / 256;

	if (copy_to_user(_tlv, scale, sizeof(scale)))

		return -EFAULT;

	return 0;

}



/*

 * parser routines begin here...
@@ -933,6 +954,12 @@ static void build_feature_ctl(struct mixer_build *state, unsigned char *desc, 
		}

		strlcat(kctl->id.name + len, control == USB_FEATURE_MUTE ? " Switch" : " Volume",

			sizeof(kctl->id.name));

		if (control == USB_FEATURE_VOLUME) {

			kctl->tlv.c = mixer_vol_tlv;

			kctl->vd[0].access |= 

				SNDRV_CTL_ELEM_ACCESS_TLV_READ |

				SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK;

		}

		break;



	default: