Re: [PATCH v2 02/14] ASoC: codecs: Add HD-Audio codec driver

Re: [PATCH v2 02/14] ASoC: codecs: Add HD-Audio codec driver

[Geert Uytterhoeven]

 	Hi Cezary,

On Wed, 11 May 2022, Cezary Rojewski wrote:
> Add generic ASoC equivalent of ALSA HD-Audio codec. This codec is
> designed to follow HDA_DEV_LEGACY convention. Driver wrapps existing
> hda_codec.c handlers to prevent code duplication within the newly added
> code. Number of DAIs created is dependent on capabilities exposed by the
> codec itself. Because of this, single solution can be applied to support
> every single HD-Audio codec type.
>
> At the same time, through the ASoC topology, platform drivers may limit
> the number of endpoints available to the userspace as codec driver
> exposes BE DAIs only.
>
> Both hda_codec_probe() and hda_codec_remove() declare their expectations
> on device's usage_count and suspended-status. This is to catch any
> unexpected behavior as PM-related code for HD-Audio has been changing
> quite a bit throughout the years.
>
> In order for codec DAI list to reflect its actual PCM capabilities, PCMs
> need to be built and that can only happen once codec device is
> constructed. To do that, a valid component->card->snd_card pointer is
> needed. Said pointer will be provided by the framework once all card
> components are accounted for and their probing can begin. Usage of
> "binder" BE DAI solves the problem - codec can be listed as one of
> HD-Audio card components without declaring any actual BE DAIs
> statically.
>
> Relation with hdac_hda:
>
> Addition of parallel solution is motivated by behavioral differences
> between hdac_hda.c and its legacy equivalent found in sound/pci/hda
> e.g.: lack of dynamic, based on codec capabilities, resource allocation
> and high cost of removing such differences on actively used targets.
> Major goal of codec driver presented here is to follow HD-Audio legacy
> behavior in 1:1 fashion by becoming a wrapper. Doing so increases code
> coverage of the legacy code and reduces the maintenance cost for both
> solutions.
>
> Signed-off-by: Cezary Rojewski <cezary.rojewski@intel.com>

Thanks for your patch, which is now commit b5df2a7dca1cc6c6 ("ASoC:
codecs: Add HD-Audio codec driver") in sound-asoc/for-next.

> --- a/sound/soc/codecs/Kconfig
> +++ b/sound/soc/codecs/Kconfig
> @@ -937,6 +937,16 @@ config SND_SOC_HDAC_HDA
> 	tristate
> 	select SND_HDA
>
> +config SND_SOC_HDA
> +	tristate "HD-Audio codec driver"
> +	select SND_HDA_EXT_CORE
> +	select SND_HDA

I am wondering if this needs a platform dependency?
Or perhaps this symbol should be made invisible, as it is selected by
SND_SOC_INTEL_AVS_MACH_HDAUDIO?  Are there any other users?

Thanks!

> +	help
> +	  This enables HD-Audio codec support in ASoC subsystem. Compared
> +	  to SND_SOC_HDAC_HDA, driver's behavior is identical to HD-Audio
> +	  legacy solution - including the dynamic resource allocation
> +	  based on actual codec capabilities.
> +
> config SND_SOC_ICS43432
> 	tristate "ICS43423 and compatible i2s microphones"
>

Gr{oetje,eeting}s,

 						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
 							    -- Linus Torvalds

Re: [PATCH v2 02/14] ASoC: codecs: Add HD-Audio codec driver

[Cezary Rojewski]

On 2022-07-05 12:20 PM, Geert Uytterhoeven wrote:
>      Hi Cezary,
> 
> On Wed, 11 May 2022, Cezary Rojewski wrote:

...

>>
>> Relation with hdac_hda:
>>
>> Addition of parallel solution is motivated by behavioral differences
>> between hdac_hda.c and its legacy equivalent found in sound/pci/hda
>> e.g.: lack of dynamic, based on codec capabilities, resource allocation
>> and high cost of removing such differences on actively used targets.
>> Major goal of codec driver presented here is to follow HD-Audio legacy
>> behavior in 1:1 fashion by becoming a wrapper. Doing so increases code
>> coverage of the legacy code and reduces the maintenance cost for both
>> solutions.
>>
>> Signed-off-by: Cezary Rojewski <cezary.rojewski@intel.com>
> 
> Thanks for your patch, which is now commit b5df2a7dca1cc6c6 ("ASoC:
> codecs: Add HD-Audio codec driver") in sound-asoc/for-next.
> 
>> --- a/sound/soc/codecs/Kconfig
>> +++ b/sound/soc/codecs/Kconfig
>> @@ -937,6 +937,16 @@ config SND_SOC_HDAC_HDA
>>     tristate
>>     select SND_HDA
>>
>> +config SND_SOC_HDA
>> +    tristate "HD-Audio codec driver"
>> +    select SND_HDA_EXT_CORE
>> +    select SND_HDA
> 
> I am wondering if this needs a platform dependency?
> Or perhaps this symbol should be made invisible, as it is selected by
> SND_SOC_INTEL_AVS_MACH_HDAUDIO?  Are there any other users?


Your feedback is much appreciated!

So, this codec-driver - HDAudio codec driver to be strict - is _generic_ 
i.e. works with any HDAudio codec type, be it Cirrus, Maxim, Conexant or 
anything else.

It makes heavy use of HDAudio library found in sound/hda/ and re-uses a 
lot of non-DSP HDAudio related code found in sound/pci/hda. It's 
basically a wrapper for logic present in ALSA (sound/) so ASoC 
(sound/soc/) users can have first class HDAudio codec support without us 
duplicating the entire implementation.

Right now the only user is avs-driver found in sound/soc/intel/avs. By 
design, any HDAudio bus driver in ASoC framework can make use of it 
though. Because of that, we decided not to couple avs-driver and this 
HDAudio codec driver tightly.


> Gr{oetje,eeting}s,

This made my day :) it's wonderful!