[PATCH] ALSA: usb-audio: Fix the mixer control range limiting issue

From: Srinivas Kandagatla
Date: Wed Aug 21 2019 - 06:02:34 EST


From: Deepa Madiregama <dmadireg@xxxxxxxxxxxxxx>

- mixer_ctl_set() function is limiting the volume level
to particular range. This results in incorrect initial
volume setting for that device.
- In USB mixer while calculating the dBmin/dBmax values
resolution factor is hardcoded to 256 which results in
populating the wrong values for dBmin/dBmax.
- Fix is to use appropriate resolution factor while
calculating the dBmin/dBmax values.

Signed-off-by: Deepa Madiregama <dmadireg@xxxxxxxxxxxxxx>
Signed-off-by: Banajit Goswami <bgoswami@xxxxxxxxxxxxxx>
Signed-off-by: Meng Wang <mwang@xxxxxxxxxxxxxx>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
---
sound/usb/mixer.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 5070a6a76ab3..a67448327d07 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -1248,8 +1248,10 @@ static int get_min_max_with_quirks(struct usb_mixer_elem_info *cval,
/* USB descriptions contain the dB scale in 1/256 dB unit
* while ALSA TLV contains in 1/100 dB unit
*/
- cval->dBmin = (convert_signed_value(cval, cval->min) * 100) / 256;
- cval->dBmax = (convert_signed_value(cval, cval->max) * 100) / 256;
+ cval->dBmin =
+ (convert_signed_value(cval, cval->min) * 100) / (cval->res);
+ cval->dBmax =
+ (convert_signed_value(cval, cval->max) * 100) / (cval->res);
if (cval->dBmin > cval->dBmax) {
/* something is wrong; assume it's either from/to 0dB */
if (cval->dBmin < 0)
--
2.21.0