Man page 9 : snd_pcm_hw_param_first

snd_pcm_hw_param_first - refine config space and return minimum value

int snd_pcm_hw_param_first(struct snd_pcm_substream *  pcm , struct snd_pcm_hw_params *  params , snd_pcm_hw_param_t  var , int *  dir );

pcm
    PCM instance

params
    the hw_params instance

var
    parameter to retrieve

dir
    pointer to the direction (-1,0,1) or NULL

Inside configuration space defined by params remove from var all values > minimum. Reduce configuration space accordingly.

The minimum, or a negative error code on failure.