linux-kernel - Re: SYSFS "errors"

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Message-ID: <20130219101121.GJ23197@arwen.pp.htv.fi>
Date:	Tue, 19 Feb 2013 12:11:21 +0200
From:	Felipe Balbi <balbi@...com>
To:	Mauro Carvalho Chehab <mchehab@...hat.com>
CC:	Borislav Petkov <bp@...en8.de>,
	Greg KH <gregkh@...uxfoundation.org>, <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"

Hi,

On Tue, Feb 19, 2013 at 07:03:10AM -0300, Mauro Carvalho Chehab wrote:
> > But my gut feeling says to stay concervative and not touch this code -
> > we don't know what uses it and how much we would break by "fixing" it.
> > The current situation is not that big of a deal IMVHO and I'd be willing
> > to accept the small inconcistency versus possibly breaking userspace.
> 
> I remember I saw some discussions about it in the past at bluesmoke ML,
> saying that -ENODEV is the expected behavior when this is not supported.
> 
> Changing from -ENODEV to "N/A" will break anything that would be relying
> on the previous behavior. So, I think that such change will for sure break
> userspace.
> 
> If we're willing to change it, not creating the "sdram_scrub_rate" sysfs 
> node is less likely to affect userspace.

yeah, I agree with this. Guess we shouldn't be creating files which
aren't supported by the underlying HW and having a read() return -ENODEV
is quite weird IMO since that's actually 'breaking' read() interface
although that's up to interpretations.

-- 
balbi

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