[alsa-devel] Missing beep controls for Via HDA codec (snd_hda_codec_via)

[W. Trevor King]

My VT1802 chip has a beep-generating node:

  $ cat /proc/asound/card1/codec#0
  Codec: VIA VT1802
  ...
  Vendor Id: 0x11068446
  Subsystem Id: 0x15587410
  Revision Id: 0x100000
  ...
  Node 0x22 [Beep Generator Widget] wcaps 0x70040c: Mono Amp-Out
    Amp-Out caps: ofs=0x0a, nsteps=0x12, stepsize=0x05, mute=1
    Amp-Out vals:  [0x0a]
    Power states:  D0 D1 D2 D3
    Power: setting=D0, actual=D0
  ...

But I'm missing the:

  Control: name=...

entries that I think I need to manage this widget from alsamixer.  For
example, sambrian posts codec output for a CX20561 chip which has [1]:

  Node 0x13 [Beep Generator Widget] wcaps 0x70000c: Mono Amp-Out
    Control: name="Beep Playback Volume", index=0, device=0
    ControlAmp: chs=1, dir=Out, idx=0, ofs=0
    Control: name="Beep Playback Switch", index=0, device=0
    ControlAmp: chs=1, dir=Out, idx=0, ofs=0
    Amp-Out caps: ofs=0x03, nsteps=0x03, stepsize=0x17, mute=0
    Amp-Out vals: [0x00]

I can patch with something like this:

  diff --git a/sound/pci/hda/patch_via.c b/sound/pci/hda/patch_via.c
  index 3de6d3d..85a0c08 100644
  --- a/sound/pci/hda/patch_via.c
  +++ b/sound/pci/hda/patch_via.c
  @@ -1520,8 +1520,10 @@ static int patch_vt2002P(struct hda_codec *codec)
          spec->gen.mixer_nid = 0x21;
          override_mic_boost(codec, 0x2b, 0, 3, 40);
          override_mic_boost(codec, 0x29, 0, 3, 40);
  -       if (spec->codec_type == VT1802)
  +       if (spec->codec_type == VT1802) {
  +               spec->gen.beep_nid = 0x22;
                  fix_vt1802_connections(codec);
  +       }
          add_secret_dac_path(codec);

          snd_hda_pick_fixup(codec, NULL, vt2002p_fixups, via_fixups);

to get a dmesg entry like:

  input: HDA Digital PCBeep as /devices/pci0000:00/0000:00:1b.0/sound/card1/hdaudioC1D0/input15

but that doesn't add the beep controls.  Looking at patch_analog.c,
patch_conexant.c, and patch_realtek.c for inspiration, I expect we'll
need an HDA_CODEC_MUTE_BEEP(_MONO) entry, and possibly an
HDA_CODEC_VOLUME(_MONO) entry, but I'm not sure if these should be
mono or not, or if they should be inputs (following patch_realtek.c)
or outputs (following patch_analog.c and patch_conexant.c).  I've
filled out Via's datasheet-request form [2], but I don't know how
likely that is to be accepted.

Does anyone have a VT1802 datasheet that they're allowed to share (or
some free time to fill in Via beep support on their own)?  Or am I
barking up the wrong tree?  My only previous experience with this
code-base was a beep-tweak for a previous box's Realtek chip [3], but
I love my beeps and am happy to poke around with a datasheet until I
get this working ;).  Maybe folks with more experience can just guess
the right code without needing to see specs for the VT1802?

Cheers,
Trevor

[1]: http://forums.fedoraforum.org/archive/index.php/t-265822.html
[2]: http://www.via.com.tw/en/support/contact_us/
[3]: http://thread.gmane.org/gmane.linux.alsa.devel/121300

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