New subject: [alsa-devel] [PATCH] [SOUND] recording gain control

10 Mar 2009

Takashi Iwai wrote:
...
  At Tue, 10 Mar 2009 10:00:13 +0100,
 Clemens Ladisch wrote:

  (CC alsa-devel)

 Viral Mehta wrote:

  Hi,

 I am trying to do gain control while RECORDING for my Audio Mic device.

 My application opens /dev/mixer device and calls ioctl(fdmixer, 
 MIXER_WRITE(SOUND_MIXER_MIC), ...)

 But, the call fails. It traces to sound/core/oss/mixer_oss.c file and 
 snd_mixer_oss_put_volume1() function.
 It never falls in "if (slot->present & SNDRV_MIXER_OSS_PRESENT_CVOLUME)"

 as condition "if (slot->present & SNDRV_MIXER_OSS_PRESENT_PVOLUME) " 
 comes as false.

 I think there is a bug in kernel and I think it should be like as below,

 --- sound/core/oss/mixer_oss.c  2008-12-03 13:24:02.000000000 +0530
 +++ sound/core/oss/mixer_oss.c   2009-03-09 16:22:06.548766896 +0530
 @@ -688,7 +688,7 @@ static int snd_mixer_oss_put_volume1(str

      if (slot->present & SNDRV_MIXER_OSS_PRESENT_PVOLUME) {
              snd_mixer_oss_put_volume1_vol(fmixer, pslot, 
 slot->numid[SNDRV_MIXER_OSS_ITEM_PVOLUME], left, right);
 -               if (slot->present & SNDRV_MIXER_OSS_PRESENT_CVOLUME)
 +       } else if (slot->present & SNDRV_MIXER_OSS_PRESENT_CVOLUME) {
                      snd_mixer_oss_put_volume1_vol(fmixer, pslot, 
 slot->numid[SNDRV_MIXER_OSS_ITEM_CVOLUME], left, right);
      } else if (slot->present & SNDRV_MIXER_OSS_PRESENT_GVOLUME) {
              snd_mixer_oss_put_volume1_vol(fmixer, pslot, 
 slot->numid[SNDRV_MIXER_OSS_ITEM_GVOLUME], left, right);
         Your mailer mangled the patch; see linux/Documentation/email-clients.txt.

 Also, the current code behaves intentionally so (as it's designed for
 mic-loopback volume).

 A more feasible fix would be to add another if check for *_CVOLUME
 instead of moving it.

    Oh okie. It makes sense.
I just sent out a patch on LAD. Should I resubmit with what you proposed ?

...
  Takashi
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Re: [LAD] [alsa-devel] [PATCH] [SOUND] recording gain control