linux-kernel - Re: [PATCH] implement set_enabled functions on powercap.c

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Message-ID: <d8cfed44-3bc0-4774-b39c-05fa0b82f6d8@linuxfoundation.org>
Date: Mon, 21 Oct 2024 14:36:58 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: Vishnu Sanal T <t.v.s10123@...il.com>, linux-pm@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, trenn@...e.com, shuah@...nel.org,
 jwyatt@...hat.com, jkacur@...hat.com, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH] implement set_enabled functions on powercap.c

On 10/19/24 06:42, Vishnu Sanal T wrote:
> Implement the functions sysfs_set_enabled, powercap_set_enabled,
> and powercap_zone_set_enabled on powercap.c.
> 
> Signed-off-by: Vishnu Sanal T <t.v.s10123@...il.com>
> ---
>   tools/power/cpupower/lib/powercap.c | 43 +++++++++++++++++++++++++----
>   1 file changed, 37 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/power/cpupower/lib/powercap.c b/tools/power/cpupower/lib/powercap.c
> index 94a0c69e55ef..1cf2b0de5536 100644
> --- a/tools/power/cpupower/lib/powercap.c
> +++ b/tools/power/cpupower/lib/powercap.c
> @@ -70,6 +70,29 @@ static int sysfs_get_enabled(char *path, int *mode)
>   	return ret;
>   }
>   
> +static int sysfs_set_enabled(char *path, int mode)
> +{
> +	int fd;
> +	char yes_no = (char) (mode + '0');
> +	int ret = 0;
> +
> +	fd = open(path, O_RDWR);
> +	if (fd == -1) {
> +		ret = -1;
> +		goto out;
> +	}
> +
> +	if (write(fd, &yes_no, 1) != 1) {
> +		ret = -1;
> +		goto out_close;
> +	}
> +
> +out_close:
> +	close(fd);
> +out:
> +	return ret;
> +}
> +

Why can't this all be simplified using system("echo 1 filename")

That goes for existing get routines.

>   int powercap_get_enabled(int *mode)
>   {
>   	char path[SYSFS_PATH_MAX] = PATH_TO_POWERCAP "/intel-rapl/enabled";
> @@ -77,12 +100,11 @@ int powercap_get_enabled(int *mode)
>   	return sysfs_get_enabled(path, mode);
>   }
>   
> -/*
> - * TODO: implement function. Returns dummy 0 for now.
> - */
>   int powercap_set_enabled(int mode)
>   {
> -	return 0;
> +	char path[SYSFS_PATH_MAX] = PATH_TO_POWERCAP "/intel-rapl/enabled";
> +
> +	return sysfs_set_enabled(path, mode);
>   }
>   
>   /*
> @@ -180,8 +202,17 @@ int powercap_zone_get_enabled(struct powercap_zone *zone, int *mode)
>   
>   int powercap_zone_set_enabled(struct powercap_zone *zone, int mode)
>   {
> -	/* To be done if needed */
> -	return 0;
> +	char path[SYSFS_PATH_MAX] = PATH_TO_POWERCAP;
> +
> +	if ((strlen(PATH_TO_POWERCAP) + strlen(zone->sys_name)) +
> +	    strlen("/enabled") + 1 >= SYSFS_PATH_MAX)
> +		return -1;
> +
> +	strcat(path, "/");
> +	strcat(path, zone->sys_name);
> +	strcat(path, "/enabled");
> +
> +	return sysfs_set_enabled(path, mode);
>   }
>   
>   

thanks,
-- Shuah