linux-kernel - Re: [PATCH v2 3/4] pwm: sysfs: Replace sprintf() with sysfs

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Message-ID: <YzRS+VIBK1AiysEN@smile.fi.intel.com>
Date:   Wed, 28 Sep 2022 16:58:17 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     linux-pwm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Subject: Re: [PATCH v2 3/4] pwm: sysfs: Replace sprintf() with sysfs_emit()

On Wed, Sep 28, 2022 at 04:40:35PM +0300, Andy Shevchenko wrote:
> On Wed, Sep 28, 2022 at 02:28:41PM +0200, Thierry Reding wrote:
> > On Fri, Aug 26, 2022 at 08:07:15PM +0300, Andy Shevchenko wrote:
> > > For sysfs outputs, it's safer to use a new helper, sysfs_emit(),
> > > instead of the raw sprintf() & co. This patch replaces such a
> > > sprintf() call straightforwardly with the new helper.
> 
> > How exactly is sysfs_emit() safer here? In all of these cases, the
> > values that sprintf() writes are the only values that are written into
> > the buffer and we know that none of them exceed PAGE_SIZE. So the
> > additional checks that sysfs_emit() performs are useless.
> 
> This is a recommended way to use sysfs_emit() mentioned in Documentation.
> Care to fix documentation?

For your convenience, Documentation/filesystems/sysfs.rst says:

- show() should only use sysfs_emit() or sysfs_emit_at() when formatting
  the value to be returned to user space.

-- 
With Best Regards,
Andy Shevchenko