Re: [PATCH v2 5/5] ASoC: pcm179x: Add support for pcm1975

["Roman Smrž" <roman@amarulasolutions.com>]

On Mon, Oct 26, 2026 at 07:09:03PM +0000, Mark Brown wrote:
> > The PCM1795 is register compatible with the PCM1792A, but it encodes two
> > of the register 18 FMT[2:0] values differently: code 001 selects 32-bit
> > standard data instead of 20-bit, and code 100 selects 32-bit I2S instead
> > of 16-bit I2S. It has no 20-bit format at all. The PCM1796 shares the
> > PCM1792A encoding.
> 
> > +	{ .compatible = "ti,pcm1795", .data = (void *)PCM1795, },
> > +	{ .compatible = "ti,pcm1796", .data = (void *)PCM1796, },
> >  	{ }
> >  };
> 
> >  static const struct spi_device_id pcm179x_spi_ids[] = {
> >  	{ "pcm1792a", 0 },
> > +	{ "pcm1795", 0 },
> 
> Don't we need to set the driver data to PCM1795 like we do for the other
> DT based entries?

Yes, I'll fix that.

> > +static const struct pcm179x_fmt_table pcm1795_fmt[] = {
> > +	{ SND_SOC_DAIFMT_RIGHT_J, 16, 0 },
> > +	{ SND_SOC_DAIFMT_RIGHT_J, 24, 2 },
> > +	{ SND_SOC_DAIFMT_RIGHT_J, 32, 1 },
> > +	{ SND_SOC_DAIFMT_LEFT_J,  24, 3 },
> > +	{ SND_SOC_DAIFMT_I2S,     24, 5 },
> > +	{ SND_SOC_DAIFMT_I2S,     32, 4 },
> 
> Does this line up with the constraints advertised by the driver?  LEFT_J
> and S32 isn't here, but S16 is?  We're also not handling big endian.

Yes, the 32bit variant for LEFT_J should be here as well. But what
should be handled for big endian here? As far as I've understood,
the bit stream on wire would be the same regardless of byte order in
memory.

> > @@ -191,7 +241,7 @@ static struct snd_soc_dai_driver pcm179x_dai = {
> >  		.rates = SNDRV_PCM_RATE_CONTINUOUS,
> >  		.rate_min = 10000,
> >  		.rate_max = 200000,
> > -		.formats = PCM1792A_FORMATS, },
> > +		.formats = PCM179X_FORMATS, },
> 
> It'd probably be easier to just register different constraints depending
> on the device rather than having constraints in startup, you'd get much
> better reuse of the core code that way.  Dynamic updates are usually
> done for things that can vary at runtime like clock rates.

After rechecking the format list, all the supported variants should have
the same "formats" field, so I can remove the distinction for that point
altogether.

Best Regrads
	Roman Smrž