Re: struct snd_pcm_ops callbacks

[Muni Sekhar <munisekharrms@xxxxxxxxx>]

On Wed, Jan 25, 2023 at 8:30 PM Pierre-Louis Bossart
<pierre-louis.bossart@xxxxxxxxxxxxxxx> wrote:
>
>
>
> On 1/25/23 05:21, Muni Sekhar wrote:
> > Hi,
> >
> > struct snd_pcm_ops callbacks can be used for sending\receiving PDM
> > audio data to and from a sound card? Or is it only designed for PCM
> > audio data?
>
> It depends what side of the sound card you are looking at, the physical
> interface with external devices or the userspace interface.
I am looking at the userspace interface side.

>
> PDM can be supported at the physical interface level as long as there is
> a conversion to PCM somewhere in the hardware. Userspace will
> play/record PCM. See examples in many codecs and SOCs.
>
> There is also the possibility of packing PDM (aka DSD) as pseudo-PCM,
> that's a trick used by several USB cards. In that case of course the
> sound card cannot apply any processing to the data and is just a
> pass-through module.
>
>


-- 
Thanks,
Sekhar