diff mbox series

ASoC: codes: src4xxx: Avoid clang -Wsometimes-uninitialized in src4xxx_hw_params()

Message ID 20220822183101.1115095-1-nathan@kernel.org
State Superseded
Headers show
Series ASoC: codes: src4xxx: Avoid clang -Wsometimes-uninitialized in src4xxx_hw_params() | expand

Commit Message

Nathan Chancellor Aug. 22, 2022, 6:31 p.m. UTC 
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.

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(-)


base-commit: 94f072748337424c9cf92cd018532a34db3a5516

Comments

Matt Flax Aug. 22, 2022, 10 p.m. UTC | #1 
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@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.
Nathan Chancellor Aug. 22, 2022, 10:32 p.m. UTC | #2 
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.

[1]: https://lore.kernel.org/CAHk-=wg-mH-_GYpkhz_psjBWG6ZcjKnPo83fg7YMj_by+-LRTQ@mail.gmail.com/
[2]: https://lore.kernel.org/CAHk-=wi4wyvuXs0SUq-2x=XHxWmJ6jVKRD-WpE0kWgWiqVJNbg@mail.gmail.com/
[3]: https://lore.kernel.org/YwNMUlAmu%2FqCjuva@debian/

> 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
Matt Flax Aug. 22, 2022, 10:35 p.m. UTC | #3 
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.
>
> [1]: https://lore.kernel.org/CAHk-=wg-mH-_GYpkhz_psjBWG6ZcjKnPo83fg7YMj_by+-LRTQ@mail.gmail.com/
> [2]: https://lore.kernel.org/CAHk-=wi4wyvuXs0SUq-2x=XHxWmJ6jVKRD-WpE0kWgWiqVJNbg@mail.gmail.com/
> [3]: https://lore.kernel.org/YwNMUlAmu%2FqCjuva@debian/
>
>> 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
diff mbox series

Patch

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;
 		}
 		ret = regmap_write(src4xxx->regmap, SRC4XXX_RCV_PLL_0F, pj);
 		if (ret < 0)