linux-kernel - Re: [PATCH 1/4] regmap: sdw: move to -EOPNOTSUPP

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Date:   Wed, 26 Aug 2020 12:22:28 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Mark Brown <broonie@...nel.org>
Cc:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        vkoul@...nel.org, gregkh@...uxfoundation.org, jank@...ence.com,
        srinivas.kandagatla@...aro.org, slawomir.blauciak@...el.com,
        Bard liao <yung-chuan.liao@...ux.intel.com>,
        Rander Wang <rander.wang@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Hui Wang <hui.wang@...onical.com>,
        Guennadi Liakhovetski <guennadi.liakhovetski@...ux.intel.com>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH 1/4] regmap: sdw: move to -EOPNOTSUPP

On Wed, 26 Aug 2020 12:13:01 +0200,
Mark Brown wrote:
> 
> On Wed, Aug 26, 2020 at 12:09:28PM +0200, Takashi Iwai wrote:
> > Mark Brown wrote:
> 
> > > checkpatch is broken.
> 
> > Heh, I'm not objecting it :)
> 
> > OTOH, it's also true that ENOTSUPP is no good error code if returned
> > to user-space.  Unfortunately many codes (including what I wrote) use
> > this code mistakenly, and they can't be changed any longer...
> 
> It's also used internally in various places without being returned to
> userspace, that's what's going on here - the regmap core has some
> specific checks for -ENOTSUPP.

Sure, for such an internal usage any code can be used.
The question is a case like this -- where the return code might be
carried to outside.  Though, looking through the grep output, all
callers simply return -EINVAL for any errors, so it doesn't matter
much for now.


BTW, there are a few callers of devm_regmap_init_sdw() checking the
return value with NULL.  This will crash as the function returns the
error pointer, and they must be checked with IS_ERR() instead.


Takashi