[PATCH] ALSA: hda: Refactor calculating SDnFMT according to specification

[Kai Vehmanen]

Hey,

On Mon, 24 Aug 2020, Pawel Harlozinski wrote:

> Set SDnFMT depending on which format was given, as maxbps only describes container size.

hmm, I'm not entirely sure that is correct. Usage may be a bit varied, but 
most places in existing code, "maxbps" is treated as number of significant 
bits, not the container size. E.g. in hdac_hda.c:

»       if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
»       »       maxbps = dai->driver->playback.sig_bits;
»       else
»       »       maxbps = dai->driver->capture.sig_bits;

It would seem "maxbps" is a bit superfluous given the same information can 
be relayed in "format" as well. But currently it's still used. E.g. if you 
look at snd_hdac_query_supported_pcm(), if codec reports 24bit support, 
format is always set to SNDRV_PCM_FMTBIT_S32_LE, even if only 24bit are 
valid. So snd_pcm_format_width() will not return the expected significant 
bits info, but you have to use "maxbps". So original code seems correct 
(or at least you'd need to update both places).

Br, Kai