[alsa-devel] PandaBoard ES Audio Problems

Clemens Ladisch clemens at ladisch.de
Thu Jan 31 20:44:25 CET 2013

Brent Weatherall wrote:
> stepping through the ALSA code, it seems the error *might* be in
> the ALSA code, but I am probably reading the code incorrectly:
> pcm/interval.c:

That code is correct (it's used in a different context).

The problem is that the kernel driver returns wrong min/max values.

> Liam Girdwood wrote:
>> The OMAP4 ABE driver doesn't actually know the exact constraints if
>> there is not a valid playback path between source PCM and sink (it will
>> still throw out anything insane though). This is because it can route
>> audio from most of it's PCMs to most of it's components, e.g. HS, HF,
>> BT, MODEM, Earpiece, etc where some components have different
>> constraints. It's possible that you dont have a path in your case.

In theory, what the driver should do is:
- don't allow the PCM device to be opened if there is no valid route
  configuration (or just never allow a completely invalid
  configuration); and
- while the PCM device is open, lock the route configuration, or
- if changing the route during playback is necessary, allow to set
  only those routes that are possible with the current PCM


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