Re: [alsa-devel] [PATCH] ASoC: skl: always select SND_SOC_HDAC_HDA

[Pierre-Louis Bossart]

> > > We have this ("strange") lines over the drivers:
> > >
> > > config BAR
> > > depends on FOO || FOO=n
> > >
> > > which guarantees that FOO will be not module when BAR is built-in.
> > That's what I normally use, but I could not figure this one out.
> > One problem is that SND_SOC_ALL_CODECS selects
> > SND_SOC_HDAC_HDA, and SND_SOC_ALL_CODECS itself
> > may be =m, causing the failure for
> > SND_SOC_INTEL_SKL_HDA_DSP_GENERIC_MACH=y.
> >
> > It might work with a separate dummy symbol:
> >
> > config SND_SOC_HDAC_HDA_FORCE
> >           tristate
> >           depends on SND_SOC_ALL_CODECS != n
> >           default SND_SOC_INTEL_SKYLAKE
> >           select SND_SOC_HDAC_HDA
> >
> > This would make SND_SOC_HDAC_HDA built-in even
> > with SND_SOC_ALL_CODECS=m and
> > SND_SOC_INTEL_SKL_HDA_DSP_GENERIC_MACH=n
> >
> > It seems a bit ugly, and would need some testing.
> The mixture of depends and select is often more confusing, so IMO, we
> should align with only select as Pierre's suggestion, in this
> particular case.

I tried to avoid re-adding a "depends on" which we tried to remove last 
year, but there is still a conditional statement which assumes a very 
specific evaluation order.

1. SKYLAKE is enabled as m or y

2. that enables some machine drivers (through an if statement), some of 
which might select HDA audio

3. the selections done within the SKYLAKE config are conditional on the 
outcome of #2.

it seems to work but I don't know if it's by design or an accident :-). 
One could argue it's a hidden "depends on".