[alsa-devel] [PATCH] sound/usb: add dB range mapping quirks.

[Yao-Wen Mao]

Thanks for the reply!

Some usb audio devices don't follow the standard specification. (1/256 dB)
I think introducing the dB conversion factor may be a good idea.
Also I think mixer_maps.c is a good place to do this.

By the way, I can't figure out the meanings of FU, MU, SU, ... etc.
Could you tell me the meanings of them?
(I guess FUs are units which have volume controls?)

The devices which I tested has only one volume control shown in alsamixer.
I don't know if there are some devices have more than one volume factor.


thanks again,

Yao-Wen

On Tue, Jul 28, 2015 at 4:17 PM, Takashi Iwai <tiwai at suse.de> wrote:

> On Tue, 28 Jul 2015 10:06:45 +0200,
> Yao-Wen Mao wrote:
> >
> > Some usb audio devices don't follow the specification of the
> > volume range. Add dB_mapping_quirks to fix some devices' dB
> > ranges so that the function snd_mixer_selem_set_playback_dB in
> > alsa-lib can set the correct value for those devices.
> >
> > Signed-off-by: Yao-Wen Mao <yaowen at google.com>
>
> This can be done also by adding to mixer_maps.c.
> The map doesn't have to contain the name string but only with a dB
> entry (I think).
>
> OTOH, this patch shows the value factor to be corrected, so it may
> make more sense -- people can look at these as a reference.
>
> One thing I wonder, though: can it be simplified by introducing the dB
> conversion factor instead?  Do these devices have other FUs that have
> a different volume factor?
>
>
> thanks,
>
> Takashi
>
> > ---
> >  sound/usb/mixer.c | 30 ++++++++++++++++++++++++++++++
> >  1 file changed, 30 insertions(+)
> >
> > diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
> > index 6b3acba..b6b27dc 100644
> > --- a/sound/usb/mixer.c
> > +++ b/sound/usb/mixer.c
> > @@ -933,6 +933,32 @@ static void volume_control_quirks(struct
> usb_mixer_elem_info *cval,
> >       }
> >  }
> >
> > +/* dB mapping quirks */
> > +static void dB_mapping_quirks(struct usb_mixer_elem_info *cval,
> > +                           struct snd_kcontrol *kctl)
> > +{
> > +     switch (cval->mixer->chip->usb_id) {
> > +     case USB_ID(0x05a7, 0x1020): /* Bose Companion 5 */
> > +             if (strcmp(kctl->id.name, "PCM Playback Volume") == 0) {
> > +                     cval->dBmin = (convert_signed_value(cval,
> cval->min) * 100) / 16;
> > +                     cval->dBmax = (convert_signed_value(cval,
> cval->max) * 100) / 16;
> > +             }
> > +             break;
> > +     case USB_ID(0x21b4, 0x0081): /* Dragonfly DAC 1.2 */
> > +             if (strcmp(kctl->id.name, "PCM Playback Volume") == 0) {
> > +                     cval->dBmin = convert_signed_value(cval,
> cval->min) * 100;
> > +                     cval->dBmax = convert_signed_value(cval,
> cval->max) * 100;
> > +             }
> > +             break;
> > +     case USB_ID(0x046d, 0x0a29): /* Logitech H800 */
> > +             if (strcmp(kctl->id.name, "PCM Playback Volume") == 0) {
> > +                     cval->dBmin = convert_signed_value(cval,
> cval->min);
> > +                     cval->dBmax = convert_signed_value(cval,
> cval->max);
> > +             }
> > +             break;
> > +     }
> > +}
> > +
> >  /*
> >   * retrieve the minimum and maximum values for the specified control
> >   */
> > @@ -1027,6 +1053,10 @@ static int get_min_max_with_quirks(struct
> usb_mixer_elem_info *cval,
> >        */
> >       cval->dBmin = (convert_signed_value(cval, cval->min) * 100) / 256;
> >       cval->dBmax = (convert_signed_value(cval, cval->max) * 100) / 256;
> > +
> > +     if (kctl)
> > +             dB_mapping_quirks(cval, kctl);
> > +
> >       if (cval->dBmin > cval->dBmax) {
> >               /* something is wrong; assume it's either from/to 0dB */
> >               if (cval->dBmin < 0)
> > --
> > 2.5.0.rc2.392.g76e840b
> >
> >
>