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

[Takashi Iwai]

On Tue, 28 Jul 2015 11:13:56 +0200,
Yao-Wen Mao wrote:
> 
> 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?)

FU = Feature Unit
MU = Mixer Unit
SU = Selector Unit


Takashi

> 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
> > >
> > >
> >
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