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.
Takashi