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

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Date:   Tue, 5 Jul 2022 12:20:38 +0200 (CEST)
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Cezary Rojewski <cezary.rojewski@...el.com>
cc:     alsa-devel@...a-project.org, broonie@...nel.org,
        upstream@...ihalf.com, kai.vehmanen@...ux.intel.com,
        harshapriya.n@...el.com, rad@...ihalf.com,
        pierre-louis.bossart@...ux.intel.com, tiwai@...e.com,
        hdegoede@...hat.com, amadeuszx.slawinski@...ux.intel.com,
        cujomalainey@...omium.org, lma@...ihalf.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 02/14] ASoC: codecs: Add HD-Audio codec driver

 	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@...el.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@...ux-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