linux-kernel - Re: drivers/char/hw_random/npcm-rng.c:166:34: warning: unused variable 'rng_dt

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Date:   Thu, 25 Jun 2020 23:52:47 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     kernel test robot <lkp@...el.com>,
        Tomer Maimon <tmaimon77@...il.com>, kbuild-all@...ts.01.org,
        clang-built-linux@...glegroups.com, linux-kernel@...r.kernel.org,
        Daniel Thompson <daniel.thompson@...aro.org>
Subject: Re: drivers/char/hw_random/npcm-rng.c:166:34: warning: unused
 variable 'rng_dt_id'

On Fri, Jun 26, 2020 at 04:42:25PM +1000, Herbert Xu wrote:
> On Tue, Jun 23, 2020 at 09:58:39PM +0800, kernel test robot wrote:
> >
> > >> drivers/char/hw_random/npcm-rng.c:166:34: warning: unused variable 'rng_dt_id' [-Wunused-const-variable]
> >    static const struct of_device_id rng_dt_id[] = {
> >                                     ^
> >    1 warning generated.
> 
> The kernel is supposed to be built with -Wno-unused-const-variable,
> so I guess this is a deficiency in clang.
> 
> Cheers,
> -- 
> Email: Herbert Xu <herbert@...dor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
> 

No deficiency in clang, it's a W=1 build, which explicitly enables
-Wunused-const-variable per scripts/Kbuild.extrawarn. The 0day team
decided to enable W=1 for all build tests, hence the comment in the
reproduce notes. A thread with discussion:

https://lore.kernel.org/lkml/202005200123.gFjGzJEH%25lkp@intel.com/

Cheers,
Nathan