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ALSA: usb-audio - Correct bogus volume dB information 

Some USB devices give bogus dB information and it screws up PA.
It's better to detect a broken value and correct it in the driver
before exposing the value to the outside.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2009-06-16 14:27:35 +02:00
parent b8e1c73f46
commit eedbdf03a2
1 changed files with 9 additions and 0 deletions
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9
sound/usb/usbmixer.c
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@ -470,6 +470,15 @@ static int mixer_vol_tlv(struct snd_kcontrol *kcontrol, int op_flag,
*/
scale[2] = (convert_signed_value(cval, cval->min) * 100) / 256;
scale[3] = (convert_signed_value(cval, cval->max) * 100) / 256;
if (scale[3] <= scale[2]) {
/* something is wrong; assume it's either from/to 0dB */
if (scale[2] < 0)
scale[3] = 0;
else if (scale[2] > 0)
scale[2] = 0;
else /* totally crap, return an error */
return -EINVAL;
}
if (copy_to_user(_tlv, scale, sizeof(scale)))
return -EFAULT;
return 0;