[alsa-devel] Question about snd_mixer_selem_get_playback_dB_range()

Tanu Kaskinen tanu.kaskinen at digia.com
Mon Mar 21 13:52:13 CET 2011


I have added code to Pulseaudio that checks that the kernel driver
returns the same values if I call
snd_mixer_selem_get_playback_dB_range() or
snd_mixer_selem_ask_playback_vol_dB() with the lowest and highest volume
steps. The reason I do this is that I've seen a driver that didn't
return correct values from _dB_range() (it's fixed nowadays), so it's
possible that the same kind of bugs will be seen in the future too.
Doing this check at Pulseaudio startup helps to detect such bugs early.

My question is about the case where the lowest volume step is mute. Is
it a bug in the driver if _dB_range() returns something else than
SND_CTL_TLV_DB_GAIN_MUTE as the min gain in such case?


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