[alsa-devel] ALSA Control Questions
tobsnyder at gmx.de
Thu Dec 3 19:30:38 CET 2009
I've got some questions concerning the ALSA control interface...
1. What is a "simple" control? I would like to use the control interface
to set more than just volume (e.g. I would like to set input gain,
output attenuation, input channel selection, output channel selection,
output channel activation...), so I am wondering if I should use
SNDRV_CTL_ELEM_IFACE_CARD or SNDRV_CTL_ELEM_IFACE_MIXER, as they are
obviously in context with "simple" control...
2. The more interesting question: as written in "Writing an alsa driver"
callbacks are basically not atomic, but I am getting BUG: scheduling
while atomic: amixer/0x00000001/430 Call Trace: .[..] in "put"
callback?? So what is meant with "basically not atomic"?? What is
allowed and what is not allowed, am I able to get hardware interrupts in
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