linux-kernel - Re: [PATCH 08/10] perf, tool: Add sysfs read file interface

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Message-ID: <1341398440.2507.100.camel@laptop>
Date:	Wed, 04 Jul 2012 12:40:40 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	acme@...hat.com, mingo@...e.hu, paulus@...ba.org,
	cjashfor@...ux.vnet.ibm.com, fweisbec@...il.com,
	eranian@...gle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/10] perf, tool: Add sysfs read file interface

On Wed, 2012-07-04 at 00:00 +0200, Jiri Olsa wrote:
> +int sysfs_read_file(const char *file, char *buf, size_t size)
> +{
> +       char path[PATH_MAX];
> +       FILE *fp;
> +       int ret = 0;
> +
> +       snprintf(path, PATH_MAX, "%s/%s", sysfs_mountpoint, file);
> +
> +       fp = fopen(path, "r");
> +       if (!fp)
> +               return -errno;
> +
> +       if (fread(buf, 1, size, fp) == 0)
> +               ret = -errno;
> +
> +       fclose(fp);
> +       return ret; 

Does sysfs guarantee a single read is complete? If not, we need a while
loop around that read until EOF or size.

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