linux-kernel - Re: SYSFS "errors"

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Message-ID: <20130219130626.GE26623@pd.tnic>
Date:	Tue, 19 Feb 2013 14:06:26 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Mauro Carvalho Chehab <mchehab@...hat.com>
Cc:	balbi@...com, Greg KH <gregkh@...uxfoundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>, JBottomley@...allels.com,
	linux-scsi@...r.kernel.org, davem@...emloft.net,
	netdev@...r.kernel.org, Doug Thompson <dougthompson@...ssion.com>,
	linux-edac@...r.kernel.org, rjw@...k.pl, linux-pm@...r.kernel.org
Subject: Re: SYSFS "errors"

On Tue, Feb 19, 2013 at 09:46:40AM -0300, Mauro Carvalho Chehab wrote:
> Ah, now I see what you're meaning. That would require to dynamically
> create a per-mci DEVICE_ATTR().

Dude, look at the code, we do that already. And you're using it with
dev_attr_sdram_scrub_rate.

Simply change the permissions of the attribute before calling
device_create_file.

pseudo:

	umode_t mode = 0;

	if (mci->set...)
		mode |= S_IWUSR;

	if (mci->get...)
		mode |= S_IRUGO;


	dev_attr_sdram_scrub_rate.attr.mode = mode;

	device_create_file(&mci->dev, &dev_attr_sdram_scrub_rate);

> No, on both cases, open() will return an error (-ENOENT against -EPERM).

What if it is a shell script doing:

cat /sys/devices/system/edac/mc/mc0/sdram_scrub_rate

or similar?

Simply fixing the permissions fixes *all* possible cases.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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