linux-kernel - Re: [PATCH] cpufreq: s3c64xx: Remove pointless NULL check in s3c64xx_cpufreq_driver

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Date:   Wed, 23 Oct 2019 08:53:02 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Nathan Chancellor <natechancellor@...il.com>, broonie@...nel.org
Cc:     Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH] cpufreq: s3c64xx: Remove pointless NULL check in
 s3c64xx_cpufreq_driver_init

On 22-10-19, 17:09, Nathan Chancellor wrote:
> When building with Clang + -Wtautological-pointer-compare:
> 
> drivers/cpufreq/s3c64xx-cpufreq.c:152:6: warning: comparison of array
> 's3c64xx_freq_table' equal to a null pointer is always false
> [-Wtautological-pointer-compare]
>         if (s3c64xx_freq_table == NULL) {
>             ^~~~~~~~~~~~~~~~~~    ~~~~
> 1 warning generated.
> 
> The definition of s3c64xx_freq_table is surrounded by an ifdef
> directive for CONFIG_CPU_S3C6410, which is always true for this driver
> because it depends on it in drivers/cpufreq/Kconfig.arm (and if it
> weren't, there would be a build error because s3c64xx_freq_table would
> not be a defined symbol).
> 
> Resolve this warning by removing the unnecessary NULL check because it
> is always false as Clang notes. While we are at it, remove the
> unnecessary ifdef conditional because it is always true.
> 
> Fixes: b3748ddd8056 ("[ARM] S3C64XX: Initial support for DVFS")

+broonie, who wrote this patch to see his views on why he kept it like
this.

> Link: https://github.com/ClangBuiltLinux/linux/issues/748
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> ---
>  drivers/cpufreq/s3c64xx-cpufreq.c | 7 -------
>  1 file changed, 7 deletions(-)
> 
> diff --git a/drivers/cpufreq/s3c64xx-cpufreq.c b/drivers/cpufreq/s3c64xx-cpufreq.c
> index af0c00dabb22..c6bdfc308e99 100644
> --- a/drivers/cpufreq/s3c64xx-cpufreq.c
> +++ b/drivers/cpufreq/s3c64xx-cpufreq.c
> @@ -19,7 +19,6 @@
>  static struct regulator *vddarm;
>  static unsigned long regulator_latency;
>  
> -#ifdef CONFIG_CPU_S3C6410
>  struct s3c64xx_dvfs {
>  	unsigned int vddarm_min;
>  	unsigned int vddarm_max;
> @@ -48,7 +47,6 @@ static struct cpufreq_frequency_table s3c64xx_freq_table[] = {
>  	{ 0, 4, 800000 },
>  	{ 0, 0, CPUFREQ_TABLE_END },
>  };
> -#endif
>  
>  static int s3c64xx_cpufreq_set_target(struct cpufreq_policy *policy,
>  				      unsigned int index)
> @@ -149,11 +147,6 @@ static int s3c64xx_cpufreq_driver_init(struct cpufreq_policy *policy)
>  	if (policy->cpu != 0)
>  		return -EINVAL;
>  
> -	if (s3c64xx_freq_table == NULL) {
> -		pr_err("No frequency information for this CPU\n");
> -		return -ENODEV;
> -	}
> -
>  	policy->clk = clk_get(NULL, "armclk");
>  	if (IS_ERR(policy->clk)) {
>  		pr_err("Unable to obtain ARMCLK: %ld\n",
> -- 
> 2.23.0

-- 
viresh