linux-kernel - Re: SYSFS "errors"

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Message-ID: <20130218221306.GA21493@pd.tnic>
Date:	Mon, 18 Feb 2013 23:13:06 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Mauro Carvalho Chehab <mchehab@...hat.com>, balbi@...com,
	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 Mon, Feb 18, 2013 at 01:54:34PM -0800, Greg KH wrote:
> Because sysfs is "one value per file" the lack of a file showing up
> shouldn't cause any userspace tools any problems, that is why we did
> things this way.
>
> But, of course, userspace programmers do know how to mess things up...

How about what I proposed earlier to Felipe:

--
diff --git a/drivers/edac/edac_mc_sysfs.c b/drivers/edac/edac_mc_sysfs.c
index 0ca1ca71157f..d2eef76d1d46 100644
--- a/drivers/edac/edac_mc_sysfs.c
+++ b/drivers/edac/edac_mc_sysfs.c
@@ -704,7 +704,7 @@ static ssize_t mci_sdram_scrub_rate_show(struct device *dev,
 	int bandwidth = 0;
 
 	if (!mci->get_sdram_scrub_rate)
-		return -ENODEV;
+		return sprintf(data, "N/A");
 
 	bandwidth = mci->get_sdram_scrub_rate(mci);
 	if (bandwidth < 0) {

--

Would that hurt the sysfs policy? In this case we *can* read the file
and it correctly tells us that scrub rate reading is not supported
instead of having a number there.

Hmm.

-- 
Regards/Gruss,
    Boris.

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