[PATCH 02/14] ASoC: codecs: Add HD-Audio codec driver

[Kai Vehmanen]

Hi,

On Fri, 6 May 2022, Pierre-Louis Bossart wrote:

>>> On 5/6/22 10:28, Cezary Rojewski wrote:
>>>> My suggestion is different: have all HD-Audio ASoC users switch to this
>>>> implementation when possible and remove the existing code along with
>>>> skylake-driver.
[...]
> I am however concerned about the lack of long-term plans and confusion
> coming having 3 different ways of dealing with HDaudio codecs on the
> same hardware platform (legacy, ASoC/SOF-Skylake, ASoC-AVS). 2 was
> already bad, I don't see how 3 is better?

fortunately most of the actual logic is in the codec drivers (in 
sound/pci/hda/), so redundancy in the asoc-to-hda wrappers is not that 
bad.

As a slight correction to the thread, hdac_hda.c does support HDMI and all 
SOF machine drivers transitioned to this a few years back (and dropped 
use of hdac_hdmi.c which is mostly duplicating code in patch_hdmi.c).

In last few years, most of the changes have been to the actual codec 
drivers and we've not really had many fixes to hdac_hda.c anymore (there 
has been a few, and indeed PM related). So in this sense this has worked 
well enough. Patches to fix bugs and add support for new hardware, have 
benefitted all users (DSP and no-DSP) and changes have been only needed at 
a single location. So this is all good.

The fixed DAI capabilities of hdac_hda.c are indeed not ideal (although in 
practise hasn't really been an issue so far) and the approach in the new 
hda.c seems indeed more robust. We do have a lot of existing machine 
drivers (and shipping DSP topologies that we need to keep working), so 
transitioning e.g. SOF machine drivers is not going to be straightforward.
For new mach drivers, this could be considered.

So while not ideal, maybe it makes sense to have two wrappers, hdac_hda.c 
for mach drivers with fixed DAI configuration, and the new hda.c that 
supports dynamic configuration (but requires mach drivers that match 
this). If the old SST driver is deprecated, we can then proceed to remove 
hdac_hdmi.c from the tree, so there's some savings.

Please do add some description to the commit+code+kconfig on how this new 
codec driver relates to hdac_hda. Otherwise it's very confusing to have 
two asoc codec drivers for the same thing.

Br, Kai