On 21/08/2019 18:05, Takashi Iwai wrote:
On Wed, 21 Aug 2019 12:02:25 +0200,
Srinivas Kandagatla wrote:
From: Deepa Madiregama <[email protected]>
- 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.
This change doesn't sound right. Basically the values returned from
USB-audio FEATURE UNIT or MIXER UNIT are always in 1/256 dB unit, per
definition. And we pass dB min/max to user-space as TLV_DB_MINMAX(),
i.e. TLV points just both min and max, no matter what scale is. I
believe that the current code is correct in this regard.
So, it's either a firmware bug that gives the wrong values back, or
the case we still don't cover, e.g. multiple RANGE values for
UAC2/UAC3.
Please check what exactly doesn't work as expected. Which value is
returned from the USB-audio device and what is wrongly interpreted.
Thanks for the detailed review.
I see https://www.usb.org/sites/default/files/audio10.pdf clearly
specifies Mixer unit is always 1/256dB units.
This patch has been carried in Qcom downstream kernels for past many
years to fix very low Initial volume setting on some USB headsets like
Logitech S-150 USB Speakers and Nokia HS-82 USB headset.
Its highly likely that its a firmware bug!, but I will try to get it
retested on latest kernel and collect some logs!
Thanks,
srini
thanks,
Takashi
Signed-off-by: Deepa Madiregama <[email protected]>
Signed-off-by: Banajit Goswami <[email protected]>
Signed-off-by: Meng Wang <[email protected]>
Signed-off-by: Srinivas Kandagatla <[email protected]>
---
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
