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Date:   Tue, 7 Jul 2020 13:24:10 -0300
From:   Arnaldo Carvalho de Melo <acme@kernel.org>
To:     Changbin Du <changbin.du@gmail.com>
Cc:     Jiri Olsa <jolsa@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 05/15] perf ftrace: factor out function
 write_tracing_file_int()
Message-ID: <20200707162410.GC1556@kernel.org>
References: <20200627133654.64863-1-changbin.du@gmail.com>
 <20200627133654.64863-6-changbin.du@gmail.com>
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Em Sat, Jun 27, 2020 at 09:36:44PM +0800, Changbin Du escreveu:
> We will reuse this function later.
> 
> Signed-off-by: Changbin Du <changbin.du@gmail.com>
> ---
>  tools/perf/builtin-ftrace.c | 17 ++++++++++++-----
>  1 file changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> index dceae70c3a22..003efa756322 100644
> --- a/tools/perf/builtin-ftrace.c
> +++ b/tools/perf/builtin-ftrace.c
> @@ -166,6 +166,17 @@ static int read_tracing_file_to_stdout(const char *name)
>  	return ret;
>  }
>  
> +static int write_tracing_file_int(const char *name, int value)
> +{
> +	char buf[16];
> +
> +	snprintf(buf, sizeof(buf), "%d", value);
> +	if (write_tracing_file(name, buf) < 0)
> +		return -1;
> +
> +	return 0;
> +}
> +
>  static int reset_tracing_cpu(void);
>  static void reset_tracing_filters(void);
>  
> @@ -296,8 +307,6 @@ static void reset_tracing_filters(void)
>  
>  static int set_tracing_depth(struct perf_ftrace *ftrace)
>  {
> -	char buf[16];
> -
>  	if (ftrace->graph_depth == 0)
>  		return 0;
>  
> @@ -306,9 +315,7 @@ static int set_tracing_depth(struct perf_ftrace *ftrace)
>  		return -1;
>  	}
>  
> -	snprintf(buf, sizeof(buf), "%d", ftrace->graph_depth);
> -
> -	if (write_tracing_file("max_graph_depth", buf) < 0)
> +	if (write_tracing_file_int("max_graph_depth", ftrace->graph_depth) < 0)
>  		return -1;

We've been consolidating these sysfs, tracefs, debugfs, hugetlbfs, etc
in tools/lib/fs/, where we have things like:

[acme@quaco perf]$ grep "int sysfs__" tools/lib/api/fs/fs.c 
static int sysfs__read_ull_base(const char *entry,
int sysfs__read_xll(const char *entry, unsigned long long *value)
int sysfs__read_ull(const char *entry, unsigned long long *value)
int sysfs__read_int(const char *entry, int *value)
int sysfs__read_str(const char *entry, char **buf, size_t *sizep)
int sysfs__read_bool(const char *entry, bool *value)
int sysfs__write_int(const char *entry, int value)
[acme@quaco perf]$ grep "int debugfs__" tools/lib/api/fs/fs.c 
[acme@quaco perf]$ grep "int sysctl__" tools/lib/api/fs/fs.c 
int sysctl__read_int(const char *sysctl, int *value)
[acme@quaco perf]$

Please take a look at tools/lib/api/fs/fs.h it already has the functions
to find the mount points, etc, so adding those there since you're
touchign this area now seems best.

- Arnaldo