linux-kernel - Re: [Bulk] Re: [PATCH 1/2] [PCI] Check that MWI bit really did get set

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Date:	Sun, 15 Oct 2006 10:45:44 -0700
From:	Andrew Morton <akpm@...l.org>
To:	Matthew Wilcox <matthew@....cx>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	David Brownell <david-b@...bell.net>,
	val_henson@...ux.intel.com, netdev@...r.kernel.org,
	linux-pci@...ey.karlin.mff.cuni.cz, linux-kernel@...r.kernel.org,
	gregkh@...e.de
Subject: Re: [Bulk] Re: [PATCH 1/2] [PCI] Check that MWI bit really did get
 set

On Sun, 15 Oct 2006 07:57:56 -0600
Matthew Wilcox <matthew@....cx> wrote:

> On Sun, Oct 15, 2006 at 03:21:22PM +0100, Alan Cox wrote:
> > Ar Sul, 2006-10-15 am 00:08 -0700, ysgrifennodd David Brownell:
> > > Since it's not an error, there should be no such printk ... which
> > > is exactly how it's coded above.
> > 
> > The underlying bug is that someone marked pci_set_mwi must-check, that's
> > wrong for most of the drivers that use it. If you remove the must check
> > annotation from it then the problem and a thousand other spurious
> > warnings go away.
> 
> There's only about 20 users of pci_set_mwi ... about 12 of them seem to
> check it, one of them uses a variable called
> compiler_warning_pointless_fix which leaves about 7 warnings to be
> removed by removing the __must_check.
> 
> However, I do believe the __must_check should be removed.  For example,
> the LSI 53c1030 has *nothing* to be done if setting MWI fails.  It just
> doesn't work, and the device copes.

If the drivers doesn't care and if it makes no difference to performance
then just delete the call to pci_set_mwi().

But if MWI _does_ make a difference to performance then we should tell
someone that it isn't working rather than silently misbehaving?
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