linux-kernel - Re: [PATCH v4 16/22] cpupower: add the function to get the sysfs value from specific table

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Date:   Fri, 19 Nov 2021 14:38:58 -0600
From:   Nathan Fontenot <nafonten@....com>
To:     Huang Rui <ray.huang@....com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Borislav Petkov <bp@...e.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Giovanni Gherdovich <ggherdovich@...e.cz>,
        linux-pm@...r.kernel.org
Cc:     Deepak Sharma <deepak.sharma@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Mario Limonciello <mario.limonciello@....com>,
        Steven Noonan <steven@...vesoftware.com>,
        Nathan Fontenot <nathan.fontenot@....com>,
        Jinzhou Su <Jinzhou.Su@....com>,
        Xiaojian Du <Xiaojian.Du@....com>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v4 16/22] cpupower: add the function to get the sysfs
 value from specific table

On 11/19/21 4:30 AM, Huang Rui wrote:
> Expose the helper into cpufreq header, then cpufreq driver can use this
> function to get the sysfs value if it has any specific sysfs interfaces.
> 
> Signed-off-by: Huang Rui <ray.huang@....com>
> ---
>  tools/power/cpupower/lib/cpufreq.c | 21 +++++++++++++++------
>  tools/power/cpupower/lib/cpufreq.h | 12 ++++++++++++
>  2 files changed, 27 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/power/cpupower/lib/cpufreq.c b/tools/power/cpupower/lib/cpufreq.c
> index c3b56db8b921..02719cc400a1 100644
> --- a/tools/power/cpupower/lib/cpufreq.c
> +++ b/tools/power/cpupower/lib/cpufreq.c
> @@ -83,20 +83,21 @@ static const char *cpufreq_value_files[MAX_CPUFREQ_VALUE_READ_FILES] = {
>  	[STATS_NUM_TRANSITIONS] = "stats/total_trans"
>  };
>  
> -
> -static unsigned long sysfs_cpufreq_get_one_value(unsigned int cpu,
> -						 enum cpufreq_value which)
> +unsigned long cpufreq_get_sysfs_value_from_table(unsigned int cpu,
> +						 const char **table,
> +						 unsigned index,
> +						 unsigned size)
>  {
>  	unsigned long value;
>  	unsigned int len;
>  	char linebuf[MAX_LINE_LEN];
>  	char *endp;
>  
> -	if (which >= MAX_CPUFREQ_VALUE_READ_FILES)
> +	if (!table && !table[index] && index >= size)

Should you validate the index before accessing table[index]

        if (!table && index >= size && !table[index])

-Nathan

>  		return 0;
>  
> -	len = sysfs_cpufreq_read_file(cpu, cpufreq_value_files[which],
> -				linebuf, sizeof(linebuf));
> +	len = sysfs_cpufreq_read_file(cpu, table[index], linebuf,
> +				      sizeof(linebuf));
>  
>  	if (len == 0)
>  		return 0;
> @@ -109,6 +110,14 @@ static unsigned long sysfs_cpufreq_get_one_value(unsigned int cpu,
>  	return value;
>  }
>  
> +static unsigned long sysfs_cpufreq_get_one_value(unsigned int cpu,
> +						 enum cpufreq_value which)
> +{
> +	return cpufreq_get_sysfs_value_from_table(cpu, cpufreq_value_files,
> +						  which,
> +						  MAX_CPUFREQ_VALUE_READ_FILES);
> +}
> +
>  /* read access to files which contain one string */
>  
>  enum cpufreq_string {
> diff --git a/tools/power/cpupower/lib/cpufreq.h b/tools/power/cpupower/lib/cpufreq.h
> index 95f4fd9e2656..107668c0c454 100644
> --- a/tools/power/cpupower/lib/cpufreq.h
> +++ b/tools/power/cpupower/lib/cpufreq.h
> @@ -203,6 +203,18 @@ int cpufreq_modify_policy_governor(unsigned int cpu, char *governor);
>  int cpufreq_set_frequency(unsigned int cpu,
>  				unsigned long target_frequency);
>  
> +/*
> + * get the sysfs value from specific table
> + *
> + * Read the value with the sysfs file name from specific table. Does
> + * only work if the cpufreq driver has the specific sysfs interfaces.
> + */
> +
> +unsigned long cpufreq_get_sysfs_value_from_table(unsigned int cpu,
> +						 const char **table,
> +						 unsigned index,
> +						 unsigned size);
> +
>  #ifdef __cplusplus
>  }
>  #endif
>