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

Viral Mehta
2009-03-10T12:31:31Z

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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