linux-kernel - Re: [alsa-devel] [PATCH] ALSA: ac97c: Fix an error handling path in 'atmel_ac97c

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Date:   Thu, 31 Aug 2017 11:35:57 +0200
From:   Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Julia Lawall <julia.lawall@...6.fr>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        perex@...ex.cz, tiwai@...e.com, arvind.yadav.cs@...il.com,
        nicolas.ferre@...rochip.com, broonie@...nel.org,
        garsilva@...eddedor.com, bhumirks@...il.com,
        alsa-devel@...a-project.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [alsa-devel] [PATCH] ALSA: ac97c: Fix an error handling path in
 'atmel_ac97c_probe()'

On 31/08/2017 at 12:04:03 +0300, Andy Shevchenko wrote:
> On Thu, 2017-08-31 at 10:23 +0200, Julia Lawall wrote:
> > 
> > On Thu, 31 Aug 2017, Alexandre Belloni wrote:
> > 
> > > On 31/08/2017 at 06:40:42 +0200, Christophe JAILLET wrote:
> > > > If 'clk_prepare_enable()' fails, we must release some resources
> > > > before
> > > > returning. Add a new label in the existing error handling path and
> > > > 'goto'
> > > > there.
> > > > 
> > > > Fixes: 260ea95cc027 ("ASoC: atmel: ac97c: Handle return value of
> > > > clk_prepare_enable.")
> > > > Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> > > 
> > > And here is the fallout of the stupid, brainless "fixing" of issues
> > > reported by static analysis tools.
> > > 
> > > This clk_prepare_enable will never fail. If it was going to fail,
> > > the
> > > platform would never boot to a point were it is able to execute that
> > > code. It is really annoying to have so much churn for absolutely 0
> > > benefit.
> > 
> > Would it be more productive to put the code back like it was before,
> > ie no
> > return value and no check, and add a comment to the definition of
> > clk_prepare_enable indicating that there are many case where the call
> > cannot fail?  Grepping through the code suggests that it is about 50-
> > 50 on
> > checking the return value or not doing so, which might suggest that
> > checking the value is often not required.
> 
> I didn't look into the code, though speculating it might be the case
> when CLK framework is not enabled, though many drivers are dependent to
> it, so, it would never fail in such cases.

It is not the case, it would return 0. Anyway, this will not happen
because that driver depends on ARCH_AT91 which selects COMMON_CLK_AT91
which selects COMMON_CLK.

> Nevertheless there might be
> other cases for CLK API to fail.
> 

The only case would be for a clock to be enabled without being prepared
and this will never happen because clk_prepare_enable is used.

This call will just never fail.

-- 
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com