[alsa-devel] Is snd_pcm_hw_constraint_mask64 really needed ?

Dear ALSA expert ,

I am working with an alsa codec driver where the driver is calling err = snd_pcm_hw_constraint_mask64(substream->runtime, SNDRV_PCM_HW_PARAM_FORMAT, formats); my driver is already setting format before that so I wonder why this function is called? Looks like it is needed to add audio constraints to substreams at open/startup time, but why ? what can be the issue if I do not call it ?

Please explain to me Takashi.

Thanks a lot in advance.