linux-kernel - Re: [PATCH] ASoC: dapm: Revert "use component prefix when checking widget names"

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Date:   Fri, 23 Jul 2021 16:17:26 +0100
From:   Richard Fitzgerald <rf@...nsource.cirrus.com>
To:     Mark Brown <broonie@...nel.org>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
CC:     <rander.wang@...ux.intel.com>, <shumingf@...ltek.com>,
        <patches@...nsource.cirrus.com>, <alsa-devel@...a-project.org>,
        <linux-kernel@...r.kernel.org>,
        Lucas Tanure <tanureal@...nsource.cirrus.com>
Subject: Re: [PATCH] ASoC: dapm: Revert "use component prefix when checking
 widget names"

On 22/07/2021 10:55, Richard Fitzgerald wrote:
> On 05/07/2021 17:50, Mark Brown wrote:
>> On Sat, Jul 03, 2021 at 01:50:34PM +0100, Richard Fitzgerald wrote:
>>
>>> That commit breaks all users of the snd_soc_component_*_pin() functions
>>> because it results in the prefix being added twice. It also breaks code
>>> that correctly uses the snd_soc_dapm_*_pin() functions.
>>
>>> Use the snd_soc_component_*_pin() functions if you want the component
>>> prefix to be prepended automatically.
>>
>>> Use the raw snd_soc_dapm_*_pin() functions if the caller has the full
>>> name that should be matched exactly.
>>
>> I'm not sure the analysis of which function to use when is correct or
>> what we want here (though it will work ATM), though looking again more
>> closely at the patch it doesn't look entirely right either.  The way
>> this used to be done, and the way that older code will most likely
>> assume things work, was that the DAPM functions would first try to match
>> on the local DAPM context before falling back to doing a global match.
>> This is what the fallback loop is intended to do, and the dapm functions
>> are passing the "search other contexts" flag into dapm_find_widget().
>>
>> I'd not expect the distinction you seem to expect between component and
>> DAPM and we probably have a bunch of older drivers that aren't working
>> correctly like the Realtek driver mentioned in the original fix.  I
>> think what needs to happen is that dapm_find_widget() needs to be
>> checking both the prefixed and non-prefixed names, and that the
>> component stuff shouldn't need to bother and just be a convenience
>> wrapper for users that happene to have a component to hand.
>> Alternatively we need to do an audit of all the non-machine drivers to
>> switch them to use the component functions exclusively (and possibly
>> some of the machine drivers as well), most of the CODEC users look to be
>> a small number of Wolfson/Cirrus ones.
>>
> 
> I don't mind if someone wants to change the core dapm functions if that
> is generally useful, providing that it also updates all callers of those
> functions to still work.
> 
> Changing the behaviour of core code to fix the Realtek driver without
> updating other callers of those functions is a problem.

Just to point out this is breaking stuff right now. It's not just
theoretical.