[alsa-devel] What is the meaning of the mask values in the pcm hw constraints struct ?

Mark Brown broonie at opensource.wolfsonmicro.com
Tue Oct 20 18:50:38 CEST 2009

On Tue, Oct 20, 2009 at 04:54:32PM +0100, Neil Jones wrote:

> I get the error "aplay: set_params:1022: Unable to install hw params:"
> I have traced the problem to a failing ioctl call
> (snd_pcm_playback_ioctl) the error occurs in snd_pcm_hw_refine when
> refining the mask for the SNDRV_PCM_HW_PARAM_ACCESS mask, all the bit
> fields in my runtime->hw_constraints are zero for this field, but the

You should set these up with snd_soc_set_runtime_hwparams() with the
flags in the info field.

> requested params have the value 7, Im not sure what this means, the
> SNDRV_PCM_ACCESS_xxx defines in asound.h only go upto 4 ?

It's a bitmask at this point, treat those values as shifts.

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