Re: [PATCH] ASoC: codes: src4xxx: Avoid clang -Wsometimes-uninitialized in src4xxx_hw_params()
From: Matt Flax
Date: Mon Aug 22 2022 - 18:35:45 EST
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@xxxxxxxxxxxxxx/
[2]: https://lore.kernel.org/CAHk-=wi4wyvuXs0SUq-2x=XHxWmJ6jVKRD-WpE0kWgWiqVJNbg@xxxxxxxxxxxxxx/
[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@xxxxxxxxx>
Reported-by: "Sudip Mukherjee (Codethink)" <sudipm.mukherjee@xxxxxxxxx>
Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
---
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