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>
diff --git a/sound/usb/usbmixer.c b/sound/usb/usbmixer.c
index f127bfd..539b427 100644
--- a/sound/usb/usbmixer.c
+++ b/sound/usb/usbmixer.c
@@ -470,6 +470,15 @@
*/
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;