Subject: Re: [PATCH 1/1] pci: Block config access during BIST (resend)
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Andi Kleen <ak@muc.de>, brking@us.ibm.com,
       Paul Mackerras <paulus@samba.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Date: Sun, 16 Jan 2005 15:01:44 +1100
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On Sun, 2005-01-16 at 00:58 +0000, Alan Cox wrote:
> On Sad, 2005-01-15 at 06:20, Benjamin Herrenschmidt wrote:
> > I'm pretty sure similar situations can happen on other archs when
> > pushing a bit on power management, especially things like handhelds
> > (though not much of them are PCI based for now).
> > 
> > That's why a "generic" mecanism to hide such devices while providing
> > cached data on config space read's would be useful to me as well.
> 
> That makes a lot of sense. So we need both a "blocked, will be back
> soon" and "this PCI device is invisible" flags. A device going into
> blocked and not coming back would presumably transition into
> "invisible".  I'm assuming we can't just delete the PCI device because
> the kernel needs to know that cell is there for future use/abuse.

Right. Though I think the "will be back soon" and "is invisible" are
pretty much the same thing. That is, in both our cases (BIST and pmac
PM), we want the device to still be visible to userland, as it actually
exist, should be properly detected by userland config tools etc..., but
may only be actually enabled when the interface is opened/used for PM
reasons.

Ben.


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