linux-kernel - Re: [PATCH] OPTIONAL: cpufreq/intel_pstate: fix debugfs_simple

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Date:   Fri, 30 Mar 2018 11:51:01 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Julia Lawall <julia.lawall@...6.fr>
Cc:     Francisco Jerez <currojerez@...eup.net>, kbuild-all@...org,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Len Brown <lenb@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        0day robot <fengguang.wu@...el.com>
Subject: Re: [PATCH] OPTIONAL: cpufreq/intel_pstate: fix debugfs_simple_attr.cocci warnings

Hi Julia,

On Thursday, March 29, 2018 9:12:06 PM CEST Julia Lawall wrote:
>  Use DEFINE_DEBUGFS_ATTRIBUTE rather than DEFINE_SIMPLE_ATTRIBUTE
>  for debugfs files.
> 
> Semantic patch information:
>  Rationale: DEFINE_SIMPLE_ATTRIBUTE + debugfs_create_file()
>  imposes some significant overhead as compared to
>  DEFINE_DEBUGFS_ATTRIBUTE + debugfs_create_file_unsafe().
> 
> Generated by: scripts/coccinelle/api/debugfs/debugfs_simple_attr.cocci

We've dropped the debugfs bits from intel_pstate entirely, so this change
is not applicable any more.

Thanks!

> Fixes: 9eec7989e762 ("OPTIONAL: cpufreq/intel_pstate: Expose LP controller parameters via debugfs.")
> CC: Francisco Jerez <currojerez@...eup.net>
> Signed-off-by: Fengguang Wu <fengguang.wu@...el.com>
> Signed-off-by: Julia Lawall <julia.lawall@...6.fr>
> ---
> 
> I don't actually know anything about this issue.  The change was suggested
> by kbuild.
> 
>  intel_pstate.c |    9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -885,7 +885,7 @@ static int lp_param_get(void *data, u64
>  	*val = *(u32 *)data;
>  	return 0;
>  }
> -DEFINE_SIMPLE_ATTRIBUTE(fops_lp_param, lp_param_get, lp_param_set, "%llu\n");
> +DEFINE_DEBUGFS_ATTRIBUTE(fops_lp_param, lp_param_get, lp_param_set, "%llu\n");
> 
>  static struct dentry *debugfs_parent;
> 
> @@ -922,9 +922,10 @@ static void intel_pstate_debug_expose_pa
>  	for (i = 0; lp_files[i].name; i++) {
>  		struct dentry *dentry;
> 
> -		dentry = debugfs_create_file(lp_files[i].name, 0660,
> -					     debugfs_parent, lp_files[i].value,
> -					     &fops_lp_param);
> +		dentry = debugfs_create_file_unsafe(lp_files[i].name, 0660,
> +						    debugfs_parent,
> +						    lp_files[i].value,
> +						    &fops_lp_param);
>  		if (!IS_ERR(dentry))
>  			lp_files[i].dentry = dentry;
>  	}
>