linux-kernel - Re: [PATCH v2] ASoC: codes: src4xxx: Avoid clang -Wsometimes-uninitialized in src4xxx_hw

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Date:   Wed, 24 Aug 2022 07:53:13 +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 v2] ASoC: codes: src4xxx: Avoid clang
 -Wsometimes-uninitialized in src4xxx_hw_params()

This looks good.

Reviewed-by: Matt Flax <flatmax@...tmax.com>

On 24/8/22 01:19, 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
>    sound/soc/codecs/src4xxx.c:280:3: error: variable 'jd' is used uninitialized whenever switch default is taken [-Werror,-Wsometimes-uninitialized]
>                    default:
>                    ^~~~~~~
>    sound/soc/codecs/src4xxx.c:293:59: note: uninitialized use occurs here
>                    ret = regmap_write(src4xxx->regmap, SRC4XXX_RCV_PLL_10, jd);
>                                                                            ^~
>    sound/soc/codecs/src4xxx.c:223:17: note: initialize the variable 'jd' to silence this warning
>            int val, pj, jd, d;
>                          ^
>                            = 0
>    sound/soc/codecs/src4xxx.c:280:3: error: variable 'pj' is used uninitialized whenever switch default is taken [-Werror,-Wsometimes-uninitialized]
>                    default:
>                    ^~~~~~~
>    sound/soc/codecs/src4xxx.c:288:59: note: uninitialized use occurs here
>                    ret = regmap_write(src4xxx->regmap, SRC4XXX_RCV_PLL_0F, pj);
>                                                                            ^~
>    sound/soc/codecs/src4xxx.c:223:13: note: initialize the variable 'pj' to silence this warning
>            int val, pj, jd, d;
>                      ^
>                        = 0
>    3 errors generated.
>
> The datasheet does not have any default values for these regmap values
> so pick some arbitrary values and print to the user that this is the
> case to silence the warnings.
>
> 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>
> Suggested-by: Matt Flax <flatmax@...tmax.com>
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
>
> v1 -> v2: https://lore.kernel.org/20220822183101.1115095-1-nathan@kernel.org/
>
> * Don't return early, just initialize the values to some arbitrary
>    numbers and try to hobble along, as other parts of the chip may be
>    functional.
>
> * Add message and comment to describe this situation.
>
>   sound/soc/codecs/src4xxx.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/sound/soc/codecs/src4xxx.c b/sound/soc/codecs/src4xxx.c
> index a8f143057b41..db4e280dd055 100644
> --- a/sound/soc/codecs/src4xxx.c
> +++ b/sound/soc/codecs/src4xxx.c
> @@ -280,9 +280,14 @@ static int src4xxx_hw_params(struct snd_pcm_substream *substream,
>   		default:
>   			/* don't error out here,
>   			 * other parts of the chip are still functional
> +			 * Dummy initialize variables to avoid
> +			 * -Wsometimes-uninitialized from clang.
>   			 */
>   			dev_info(component->dev,
> -				"Couldn't set the RCV PLL as this master clock rate is unknown\n");
> +				"Couldn't set the RCV PLL as this master clock rate is unknown. Chosen regmap values may not match real world values.\n");
> +			pj = 0x0;
> +			jd = 0xff;
> +			d = 0xff;
>   			break;
>   		}
>   		ret = regmap_write(src4xxx->regmap, SRC4XXX_RCV_PLL_0F, pj);
>
> base-commit: 94f072748337424c9cf92cd018532a34db3a5516