linux-kernel - Re: [PATCH] cpufreq:core: Fix printing of governor and driver name

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Date:	Mon, 15 Oct 2012 19:51:18 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	cpufreq@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linaro-dev@...ts.linaro.org,
	patches@...aro.org, Sudeep.KarkadaNagesha@....com,
	Robin.Randhawa@....com, Arvind.Chauhan@....com
Subject: Re: [PATCH] cpufreq:core: Fix printing of governor and driver name

On Wednesday 10 of October 2012 10:12:11 Viresh Kumar wrote:
> Arrays for governer and driver name are of size CPUFREQ_NAME_LEN or 16.
> i.e. 15 bytes for name and 1 for trailing '\0'.
> 
> When cpufreq driver print these names (for sysfs), it includes '\n' or ' ' in
> the fmt string and still passes length as CPUFREQ_NAME_LEN. If the driver or
> governor names are using all 15 fields allocated to them, then the trailing '\n'
> or ' ' will never be printed. And so commands like:
> 
> root@...aro-developer# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver
> 
> will print something like:
> 
> cpufreq_foodrvroot@...aro-developer#
> 
> Fix this by increasing print length by one character.
> 
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>

Thanks for the patch, I'll queue it up for v3.8.

Rafael


> ---
>  drivers/cpufreq/cpufreq.c | 6 +++---
>  include/linux/cpufreq.h   | 2 ++
>  2 files changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 021973b..db6e337 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -445,7 +445,7 @@ static ssize_t show_scaling_governor(struct cpufreq_policy *policy, char *buf)
>  	else if (policy->policy == CPUFREQ_POLICY_PERFORMANCE)
>  		return sprintf(buf, "performance\n");
>  	else if (policy->governor)
> -		return scnprintf(buf, CPUFREQ_NAME_LEN, "%s\n",
> +		return scnprintf(buf, CPUFREQ_NAME_PLEN, "%s\n",
>  				policy->governor->name);
>  	return -EINVAL;
>  }
> @@ -491,7 +491,7 @@ static ssize_t store_scaling_governor(struct cpufreq_policy *policy,
>   */
>  static ssize_t show_scaling_driver(struct cpufreq_policy *policy, char *buf)
>  {
> -	return scnprintf(buf, CPUFREQ_NAME_LEN, "%s\n", cpufreq_driver->name);
> +	return scnprintf(buf, CPUFREQ_NAME_PLEN, "%s\n", cpufreq_driver->name);
>  }
>  
>  /**
> @@ -512,7 +512,7 @@ static ssize_t show_scaling_available_governors(struct cpufreq_policy *policy,
>  		if (i >= (ssize_t) ((PAGE_SIZE / sizeof(char))
>  		    - (CPUFREQ_NAME_LEN + 2)))
>  			goto out;
> -		i += scnprintf(&buf[i], CPUFREQ_NAME_LEN, "%s ", t->name);
> +		i += scnprintf(&buf[i], CPUFREQ_NAME_PLEN, "%s ", t->name);
>  	}
>  out:
>  	i += sprintf(&buf[i], "\n");
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index b60f6ba..fc4b785 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -22,6 +22,8 @@
>  #include <asm/div64.h>
>  
>  #define CPUFREQ_NAME_LEN 16
> +/* Print length for names. Extra 1 space for accomodating '\n' in prints */
> +#define CPUFREQ_NAME_PLEN (CPUFREQ_NAME_LEN + 1)
>  
>  
>  /*********************************************************************
> 
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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