[alsa-devel] How to correct params_format on DPCM ?

[Kuninori Morimoto]

Hi Mark, Lars, all

Now, I'm using DPCM based sound, but FE/BE gets different
params format. How to correct it ?
This sound can be used both non-DPCM card / DPCM card

-- non-DPCM card --
 cpu:   rsnd
 codec: ak4642

-- DPCM card --
FE : cpu:   rsnd
     codec: snd-soc-dummy

BE : cpu:   snd-soc-dummy
     codec: ak4642


Here, SNDRV_PCM_FMTBIT_S16_LE is always selected on non-DPCM card.
This is OK.

	rsnd:   SNDRV_PCM_FMTBIT_S24_LE | SNDRV_PCM_FMTBIT_S16_LE
	ak4642: SNDRV_PCM_FMTBIT_S16_LE

On DPCM card, FE gets S24, BE gets S16 if aplay selects S24 wav.
But, FE needs S16, same as non-DPCM card.
I know we can fixup BE side via dai_link.be_hw_params_fixup,
but this is FE side.

It can't use correct sound playback in corrent DPCM card.
But, how to solve this issue ?? 

Best regards
---
Kuninori Morimoto