linux-kernel - Re: [PATCH] CHROMIUM: ASoC: amd: acp: Add tdm support for codecs in machine driver

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Date:   Mon, 7 Nov 2022 08:14:47 -0600
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Venkata Prasad Potturu <venkataprasad.potturu@....com>,
        Mark Brown <broonie@...nel.org>
Cc:     alsa-devel@...a-project.org, Sunil-kumar.Dommati@....com,
        ssabakar@....com, Ajit Kumar Pandey <AjitKumar.Pandey@....com>,
        ye xingchen <ye.xingchen@....com.cn>,
        Basavaraj.Hiregoudar@....com, Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Venkata Prasad Potturu 
        <venkataprasad.potturu@....corp-partner.google.com>,
        Vijendar.Mukunda@....com, vsujithkumar.reddy@....com,
        Akihiko Odaki <akihiko.odaki@...il.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] CHROMIUM: ASoC: amd: acp: Add tdm support for codecs in
 machine driver



On 11/7/22 04:34, Venkata Prasad Potturu wrote:
> 
> On 11/2/22 17:02, Mark Brown wrote:
>>> On 11/1/22 20:01, Mark Brown wrote:
>>>> On Tue, Nov 01, 2022 at 03:15:08PM +0530, Venkata Prasad Potturu wrote:
>>>> Right, that's what the code does but why is this something that should
>>>> be controlled in this fashion?
>>> This machine driver is common for TDM mode and I2S mode, user can
>>> select TDM
>>> mode or I2S mode.
>> Why would the user choose one value or the other, and why would this
>> choice be something that only changes at module load time?  If this is
>> user controllable I'd really expect it to be runtime controllable.
>> You're not explaining why this is a module parameter.
> 
> Different vendors/OEM's use the same hardware as one need I2S mode and
> other need TDM mode, using common driver  to support  I2S and TDM mode
> with this parameter.
> 
> 
> static int tdm_mode = 0;
> module_param_named(tdm_mode, tdm_mode, int, 0444);
> 
> And this can be runtime controllable by setting permissions as 0644, we
> will change and send next version patch.

kernel parameters are difficult to manage for distributions using a
single-build. Either all platforms use the kernel parameter or none of
them do. That would not allow a per-platform choice of parameters.
Using DMI quirks or ACPI identifiers would be a lot less problematic, no?