linux-kernel - Re: Possible issue with dangling PCI BARs

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Date:	Thu, 13 Dec 2007 12:04:17 -0800
From:	Jesse Barnes <jesse.barnes@...el.com>
To:	benh@...nel.crashing.org
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Ivan Kokshaysky <ink@...assic.park.msu.ru>,
	Robert Hancock <hancockr@...w.ca>,
	linux-pci@...ey.karlin.mff.cuni.cz,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: Possible issue with dangling PCI BARs

On Thursday, December 13, 2007 3:20 Benjamin Herrenschmidt wrote:
> > > Supporting pci_enable_device_io / pci_enable_device_mmio /
> > > pci_iomap_io / pci_iomap_mmio seems to cover pretty much all the
> > > use cases we have.
> > >
> > > The users we have right now that are:
> > >
> > >         - pata_cs5520   (can be dealt with easily)
> > >         - old IDE       (with the new resource handling for
> > > legacy IDE can use pci_enable_device_io I think, ditto
> > > pci/cs5520)
> > >         - scx200_acb    (looks like a simple substitution works)
> > >         - lpfc          pci_enable_device_mmio
> > >         - qla2xxx       pci_enable_device ? (enables IO and MMIO)
>
> I may have not fully undestood you in my previous reply. You are
> proposing replacing pci_enable_device_bars() with a pair of
> pci_enable_device_io/mem ?
>
> I think that would be a good idea indeed.

Yeah, that seems like a reasonable compromise.  Though in practice I'd 
expect the full disable decode approach to work fairly well too.  I 
mean, if we really end up failing to allocate space for the device with 
the root drive on it, there are probably bigger issues than just 
failing to get a few bytes of I/O space for it...

OTOH like Robert said, many devices really only need either MMIO or IO 
space enabled, not both, so having separate enable/disable routines for 
them makes a lot of sense.

Jesse
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