linux-kernel - Re: [PATCH v2 1/6] cpufreq/amd-pstate: Use sysfs_match

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Message-ID: <aO9fcenyZ5SgReMK@BLRRASHENOY1.amd.com>
Date: Wed, 15 Oct 2025 14:16:41 +0530
From: "Gautham R. Shenoy" <gautham.shenoy@....com>
To: "Mario Limonciello (AMD)" <superm1@...nel.org>
Cc: Perry Yuan <perry.yuan@....com>,
	"open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <linux-kernel@...r.kernel.org>,
	"open list:CPU FREQUENCY SCALING FRAMEWORK" <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v2 1/6] cpufreq/amd-pstate: Use sysfs_match_string() for
 epp

On Thu, Oct 09, 2025 at 11:17:51AM -0500, Mario Limonciello (AMD) wrote:
> Rather than scanning the buffer and manually matching the string
> use the sysfs macros.
> 
> Signed-off-by: Mario Limonciello (AMD) <superm1@...nel.org>

The patch looks good to me.
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@....com>

> ---
> v2:
>  * Drop NULL from energy_perf_strings too (Gautham)
> ---
>  drivers/cpufreq/amd-pstate.c | 15 ++++-----------
>  1 file changed, 4 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index b44f0f7a5ba1c..0bc5013448873 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -118,7 +118,6 @@ static const char * const energy_perf_strings[] = {
>  	[EPP_INDEX_BALANCE_PERFORMANCE] = "balance_performance",
>  	[EPP_INDEX_BALANCE_POWERSAVE] = "balance_power",
>  	[EPP_INDEX_POWERSAVE] = "power",
> -	NULL
>  };
>  
>  static unsigned int epp_values[] = {
> @@ -1137,16 +1136,15 @@ static ssize_t show_amd_pstate_hw_prefcore(struct cpufreq_policy *policy,
>  static ssize_t show_energy_performance_available_preferences(
>  				struct cpufreq_policy *policy, char *buf)
>  {
> -	int i = 0;
> -	int offset = 0;
> +	int offset = 0, i;
>  	struct amd_cpudata *cpudata = policy->driver_data;
>  
>  	if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE)
>  		return sysfs_emit_at(buf, offset, "%s\n",
>  				energy_perf_strings[EPP_INDEX_PERFORMANCE]);
>  
> -	while (energy_perf_strings[i] != NULL)
> -		offset += sysfs_emit_at(buf, offset, "%s ", energy_perf_strings[i++]);
> +	for (i = 0; i < ARRAY_SIZE(energy_perf_strings); i++)
> +		offset += sysfs_emit_at(buf, offset, "%s ", energy_perf_strings[i]);
>  
>  	offset += sysfs_emit_at(buf, offset, "\n");
>  
> @@ -1157,15 +1155,10 @@ static ssize_t store_energy_performance_preference(
>  		struct cpufreq_policy *policy, const char *buf, size_t count)
>  {
>  	struct amd_cpudata *cpudata = policy->driver_data;
> -	char str_preference[21];
>  	ssize_t ret;
>  	u8 epp;
>  
> -	ret = sscanf(buf, "%20s", str_preference);
> -	if (ret != 1)
> -		return -EINVAL;
> -
> -	ret = match_string(energy_perf_strings, -1, str_preference);
> +	ret = sysfs_match_string(energy_perf_strings, buf);
>  	if (ret < 0)
>  		return -EINVAL;
>  
> -- 
> 2.43.0
> 

-- 
Thanks and Regards
gautham.