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".