int snd_pcm_hw_param_mask (snd_pcm_t * pcm, snd_pcm_hw_params_t * params, snd_pcm_hw_param_t var, const snd_mask_t * val);
Inside configuration space defined by PARAMS remove from PAR all values not contained in MASK. Reduce configuration space accordingly. This function can be called only for SNDRV_PCM_HW_PARAM_ACCESS, SNDRV_PCM_HW_PARAM_FORMAT, SNDRV_PCM_HW_PARAM_SUBFORMAT. Return 0 on success or -EINVAL if the configuration space is empty