Re: [PATCH v2] implement set_enabled functions on powercap.c

["John B. Wyatt IV" <jwyatt@redhat.com>]

On Wed, Oct 30, 2024 at 08:57:07PM +0530, 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@gmail.com>
> ---
> Changes in v2:
> 
> - simplify the implementation of sysfs_set_enabled using system()
>   function.

Hello Vishnu,

Ty for sending a patch to implement this.

I got several warnings trying to compile your patch. Please resolve
them. I have not tested your code yet. How are you testing your code?

> ---
>  tools/power/cpupower/lib/powercap.c | 31 +++++++++++++++++++++++------
>  1 file changed, 25 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/power/cpupower/lib/powercap.c b/tools/power/cpupower/lib/powercap.c
> index 94a0c69e55ef..a2c0c33b7729 100644
> --- a/tools/power/cpupower/lib/powercap.c
> +++ b/tools/power/cpupower/lib/powercap.c
> @@ -70,6 +70,17 @@ static int sysfs_get_enabled(char *path, int *mode)
>  	return ret;
>  }
>  
> +static int sysfs_set_enabled(char *path, int mode)
> +{
> +	char command[SYSFS_PATH_MAX + 10];
> +
> +	char yes_no = (char)(mode + '0');

What does yes or no mean for setting a value?

`is_set` or using something with the word 'mode' would be a better
variable name?

> +
> +	sprintf(command, "echo -n %c > %s", yes_no, path);
> +
> +	return system(command);
> +}
> +

In function ‘sysfs_set_enabled’,
    inlined from ‘powercap_set_enabled’ at lib/powercap.c:95:9:
lib/powercap.c:79:9: note: ‘sprintf’ output between 13 and 267 bytes into a destination of size 265
   79 |         sprintf(command, "echo -n %c > %s", yes_no, path);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
lib/powercap.c: In function ‘powercap_zone_set_enabled’:
lib/powercap.c:79:40: warning: ‘%s’ directive writing up to 254 bytes into a region of size 253 [-Wformat-overflow=]
   79 |         sprintf(command, "echo -n %c > %s", yes_no, path);
      |                                        ^~
......
  203 |         return sysfs_set_enabled(path, mode);
      |                                  ~~~~   
In function ‘sysfs_set_enabled’,
    inlined from ‘powercap_zone_set_enabled’ at lib/powercap.c:203:9:
lib/powercap.c:79:9: note: ‘sprintf’ output between 13 and 267 bytes into a destination of size 265
   79 |         sprintf(command, "echo -n %c > %s", yes_no, path);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

>  int powercap_get_enabled(int *mode)
>  {
>  	char path[SYSFS_PATH_MAX] = PATH_TO_POWERCAP "/intel-rapl/enabled";
> @@ -77,12 +88,11 @@ 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);
>  }

lib/powercap.c: In function ‘powercap_set_enabled’:
lib/powercap.c:79:40: warning: ‘%s’ directive writing up to 254 bytes into a region of size 253 [-Wformat-overflow=]
   79 |         sprintf(command, "echo -n %c > %s", yes_no, path);
      |                                        ^~
......
   95 |         return sysfs_set_enabled(path, mode);

>  
>  /*
> @@ -180,8 +190,17 @@ 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);
>  }
>  

>  
> -- 
> 2.47.0
> 

-- 
Sincerely,
John Wyatt
Software Engineer, Core Kernel
Red Hat