Subject: Re: [PATCH 1/1] pci: Block config access during BIST (resend)
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Andi Kleen <ak@muc.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>, brking@us.ibm.com,
       Paul Mackerras <paulus@samba.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Date: Mon, 17 Jan 2005 07:53:17 +1100
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On Sun, 2005-01-16 at 05:48 +0100, Andi Kleen wrote:
> > 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.
> 
> I just request that this shouldn't be done in the low level pci_config_read_*
> functions. Please keep them simple and lean. If you want such complex 
> semantics for user space do it in a separate layer.

What is complex in there ? I agree it's not convenient to do this from
the very low level ones that don't take the pci_dev * as an argument,
but from the higher level ones that does, the overhead is basically to
test a flag in the pci_dev, I doubt it will be significant in any way
performance wise, especially compared to the cost of a config space
access...

Ben.


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