linux-kernel - Re: PCI: pci_restore_state() is returning 0 when it fails

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Message-Id: <1258382974.2841.23.camel@achroite.uk.solarflarecom.com>
Date:	Mon, 16 Nov 2009 14:49:34 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Breno Leitao <leitao@...ux.vnet.ibm.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux PCI <linux-pci@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	linux-net-drivers@...arflare.com
Subject: Re: PCI: pci_restore_state() is returning 0 when it fails

On Mon, 2009-11-16 at 12:13 -0200, Breno Leitao wrote:
> Hi Rafael, 
> 
> Rafael J. Wysocki wrote:
> > On Friday 13 November 2009, Breno Leitao wrote:
> >> Actually pci_restore_state() is returning 0 if the restore process
> >> fails, instead of a error value.
> >>
> >> If it fails, I believe that it should return -EPERM, once that
> >> it is an invalid operation and probably pci_save_state() wasn't
> >> called.
> > 
> > I believe this patch will break a number of things.
> Well, I checked it, and found that there are around 10 places that
> really verify the return value for this function, and almost all of them
> do the correct thing, and the patch doesn't seem to break any of them
> except a specific case in the drivers/net/sfc/falcon.c file, that contains:
[...]
> That's because the code is calling pci_restore_state() twice without calling
> pci_save_state() in the middle. 
> Since this seems to be the only place that will be broken, and the fix is
> trivial, I believe that the patch can be applied smoothly.
[...]

This code supports two similar PCI devices, one of which has a second
function that is not truly independent.  For that chip it saves and
restores both functions' config space.  So far as I know, there are no
cases where it fails to match save and restore.

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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