[alsa-devel] Question about your DSP topic branch - hw param fix up query

Patrick Lai plai at codeaurora.org
Thu Mar 31 19:45:23 CEST 2011

Change subject

> static int dmic_be_hw_params_fixup(struct snd_soc_pcm_runtime *rtd,
> 			struct snd_pcm_hw_params *params)
> {
> 	struct snd_interval *rate = hw_param_interval(params,
> 	/* The ABE will covert the FE rate to 96k */
> 	rate->min = rate->max = 96000;
> 	snd_mask_set(&params->masks[SNDRV_PCM_HW_PARAM_FORMAT -
> 	                            SNDRV_PCM_HW_PARAM_FIRST_MASK],
> 	                            SNDRV_PCM_FORMAT_S32_LE);
> 	return 0;
> }

For sample rate conversion case, supplying back-end hw_params_fixup 
function would work. However, I am looking for run-time configuration of 
back-end channel mode. For scenario of multi-channel microphone input, I 
need to have a mean to specify channel mode of back-end depending on 
algorithm running on DSP while front-end channel mode is mono. Is there 
a hook in the framework to do that?


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