Re: [PATCH] ASoC: codes: src4xxx: Avoid clang -Wsometimes-uninitialized in src4xxx_hw_params()

That solution looks good.

Matt

On 23/8/22 08:32, Nathan Chancellor wrote:

Hi Matt,

On Tue, Aug 23, 2022 at 08:00:07AM +1000, Matt Flax wrote:

...

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.

Okay, I could do something like this?

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);

These warnings need to be eliminated because Linus requires a clean build as much as possible [1] [2], which has been codified by CONFIG_WERROR, which is enabled by default with allmodconfig. As a result, clang allmodconfig builds are broken [3], which you might have already seen. If there is another way this could be written without potentially uninitialized variables, I am open to it.

...

All a bit messy really.

Indeed :/

...

...

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@intel.com Reported-by: "Sudip Mukherjee (Codethink)" sudipm.mukherjee@gmail.com Signed-off-by: Nathan Chancellor nathan@kernel.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.

I'll send a v2 tomorrow morning (for me at least) if there are no other comments.

Cheers, Nathan