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Message-ID: <3A36183F.1EBD9368@agelectronics.co.uk>
Date: Tue, 12 Dec 2000 12:21:19 +0000
From: Adrian Cox <apc@agelectronics.co.uk>
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To: "David S. Miller" <davem@redhat.com>
CC: groudier@club-internet.fr, mj@suse.cz, lk@tantalophile.demon.co.uk,
        davej@suse.de, linux-kernel@vger.kernel.org
Subject: Re: pdev_enable_device no longer used ?
In-Reply-To: <Pine.LNX.4.10.10012112207400.2144-100000@linux.local> <200012112221.OAA01081@pizda.ninka.net>
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"David S. Miller" wrote:
> Interpreting physical BAR values is another issue altogether.  Kernel
> wide interfaces for this may be easily added to include/asm/pci.h
> infrastructure, please just choose some sane name for it and I will
> compose a patch ok? :-)

There's a semi-respectable use for BAR values: peer-to-peer mastering. 
A new kernel interface could actually make that portable, eg:

int pci_peer_master_address(struct pci_dev *master,
	struct pci_dev *target, int resource, unsigned long offset,
	unsigned long *address);
Return values PCI_PEER_OK, PCI_PEER_NOWAY, PCI_PEER_FXBUG,
PCI_PEER_YOURE_JOKING_RIGHT, ... Bus address usable by master placed in
address.

Implementing something like this with a single hostbridge is simple.
It's  harder on boards like my Intel 840 motherboard here, where the
33MHz and 66MHz buses don't talk to each other. It could eventually grow
into a big list of platform specific workarounds, but at least they'd
all be in one place where we could see them.


- Adrian Cox, AG Electronics
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