Re: [PATCH 2/4] ALSA: hda: Make snd_hda_codec_device_init() the only codec constructor

[Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>]

On 7/20/22 10:39, Cezary Rojewski wrote:
> On 2022-07-20 3:13 PM, Takashi Iwai wrote:
>> On Wed, 20 Jul 2022 15:06:20 +0200,
>> Cezary Rojewski wrote:
>>>
>>> Refactor snd_hdac_ext_bus_device_init() so that it makes use of
>>> snd_hda_codec_device_init() to create and initialize new codec device.
>>> Causes the latter to become the sole codec device constructor.
>>>
>>> Users of the refactored function are updated accordingly and now also
>>> take responsibility for assigning driver's private data as that task is
>>> no longer performed by hdac_hda_dev_probe().
>>
>> Hrm, this doesn't look really right.  It means you'll introduce a hard
>> dependency chain in a reverse order: snd-hda-ext-core ->
>> snd-hda-codec.
>>
>> Originally, the ext bus code was written completely independent from
>> the legacy HD-audio implementations, and hdac-hda driver was a kind of
>> wrapper / bridge for the legacy codec over the ext bus.  If we want
>> change this rule and make the legacy HD-audio codec always tied with
>> the ext bus, a likely better way would be to call
>> snd_hda_codec_device_init() in the caller's side (e.g. skl or sof),
>> then pass the newly created codec object to
>> snd_hdac_ext_bus_device_init() for further initialization.
> 
> 
> Agree. That or drop the snd_hdac_ext_bus_device_init() entirely. Will
> send an update soon.
> 
> In regard to the other subject, my plan:
> - separate code used by both ALSA/ASoC into sound/hda (this includes
> many hda_codec functions)
> - combine hda_bus and hdac_bus
> - combine hda_codec and hdac_device
> - drop HDA_DEV_ASOC
> - drop hdac_hda/hdac_hdmi (once skylake-driver is gone; sof will be
> updated accordingly)

the skylake driver cannot be removed until you have evidence that users
have switched, and SOF has other priorities that will likely conflict
with that goal. I don't even know what this 'drop hdac_hda' idea means
in detail, we need to keep an ASoC-based codec and the split between
platform/codec/machine. We are not going to move the HDaudio codec
management logic inside the SOF driver if that was the intent. The SOF
driver will focus on host/controller/DSP handling.

> <story does not end here>

I strongly recommend that we add no dependencies between hdac_ext and
hda_codec. To be clearer, we don't want to limit the hdac_ext bus and
stream management to platforms with HDaudio codecs.