linux-kernel - Re: [PATCH] ASoC: codes: src4xxx: Avoid clang -Wsometimes-uninitialized in src4xxx_hw

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Message-ID: <72de09df-5dee-8bd0-5c91-359e4bc36ca8@flatmax.com>
Date:   Tue, 23 Aug 2022 08:00:07 +1000
From:   Matt Flax <flatmax@...tmax.com>
To:     Nathan Chancellor <nathan@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        patches@...ts.linux.dev, kernel test robot <lkp@...el.com>,
        "Sudip Mukherjee (Codethink)" <sudipm.mukherjee@...il.com>
Subject: Re: [PATCH] ASoC: codes: src4xxx: Avoid clang
 -Wsometimes-uninitialized in src4xxx_hw_params()

Hi Nathan,

On 23/8/22 04:31, Nathan Chancellor wrote:
> Clang warns:
>
>    sound/soc/codecs/src4xxx.c:280:3: error: variable 'd' is used uninitialized whenever switch default is taken [-Werror,-Wsometimes-uninitialized]
>                    default:
>                    ^~~~~~~
>    sound/soc/codecs/src4xxx.c:298:59: note: uninitialized use occurs here
>                    ret = regmap_write(src4xxx->regmap, SRC4XXX_RCV_PLL_11, d);
>                                                                            ^
>    sound/soc/codecs/src4xxx.c:223:20: note: initialize the variable 'd' to silence this warning
>            int val, pj, jd, d;
>                              ^
>                              = 0


If you really want to get rid of these warnings, you can use this 
default for the variables :

pj = 0x0;
jd=0xff;

d = 0xff;

It doesn't really make sense why we would choose to initialise these 
variables, but if you want to silence the preprocessor, then perhaps 
those values. Put a message that defaults are not known nor specified in 
the data sheet and these values are chosen to be unlikely matches of 
real world values - which ensures regmap updates later from an initial 
unknown chip state after refresh. All a bit messy really.


> According to the comment in the default case, other parts of the chip
> are still functional without these values so just return 0 in the
> default case to avoid using these variables uninitialized.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/1691
> Reported-by: kernel test robot <lkp@...el.com>
> Reported-by: "Sudip Mukherjee (Codethink)" <sudipm.mukherjee@...il.com>
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
>   sound/soc/codecs/src4xxx.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/sound/soc/codecs/src4xxx.c b/sound/soc/codecs/src4xxx.c
> index a8f143057b41..cf45caa4bf7f 100644
> --- a/sound/soc/codecs/src4xxx.c
> +++ b/sound/soc/codecs/src4xxx.c
> @@ -283,7 +283,7 @@ static int src4xxx_hw_params(struct snd_pcm_substream *substream,
>   			 */
>   			dev_info(component->dev,
>   				"Couldn't set the RCV PLL as this master clock rate is unknown\n");
> -			break;
> +			return 0;


Don't return here, the rest of the chip is still functional and probably 
in use. Print the dev_info and continue.