Re: PCI bus numbering and orphaned devices

On Wed, 2003/06/11 at 08:34:39 -0600, M. Warner Losh wrote:
> In message: <20030611142627.GB634_at_crow.dom2ip.de>
>             Thomas Moestl <t.moestl_at_tu-bs.de> writes:
> : On Tue, 2003/06/10 at 16:41:44 -0700, John-Mark Gurney wrote:
> : > Thomas Moestl wrote this message on Wed, Jun 11, 2003 at 01:02 +0200:
> : > Ok, the only problem is that is then we have the same problem the ACPI
> : > code does in that hot swapping cards would have a problem.  Since it
> : > appears to me that the OFW tree doesn't get updated upon a swap.  (At
> : > least the usb part of the tree doesn't.)
> : 
> : We do not support hotplugging at the moment anyway. If a bridge driver
> : would implement that in the future without using any firmware support
> : however, it will then need to know everything information about the
> : interrupt routing required for its devices if it cannot use the
> : firmware for this. in that case, it can just prevent the ofw_pci bus
> : from attaching to it (this will be easily possible).
> : I'd hope that machines that support hot-plugging of PCI devices would
> : have firmware methods available to support that though.
> 
> We'll need to do so for the cardbus bridges.

Yes, I was just speaking of PCI.

> However, the interupt is routed to the bridge and has to be shared
> with the cardbus/pccard cards.

That should be far less of a problem with the new code, since it will
make interrupt routing work right finally (right now, everything needs
to be prerouted).
 
> : > Does this mean that we should eliminate most of the Sun specific pci
> : > bus drivers in favor of OFW specific ones like ACPI? or?
> : 
> : No, it means introducing an OFW bus driver, which uses the firmware to
> : enumerate the devices and to support interrupt routing. The bridge
> : drivers would be mostly unaffected by this.
> : The only problem with this approach is that it can change the device
> : enumeration; I hope that the resulting one will be the same one that is
> : printed on the boxen, so it should be advantageous for new
> : installations, but a minor migration problem for old ones.
> : 
> : I've got some code for this already, it just isn't done yet.
> 
> So are you talking about doing something akin to the acpi bridge code
> or something else?  Would this more properly be called a OFW PCI bus
> driver,

Yes, that's what I meant to say. It will "override" some of the PCI
methods (by using it's own method table), and use the rest of them
unaltered. It will attach to PCI bridges which offer an additional
method to get the firmware device node (but with a higher priority
than the standard PCI bus), so bridges can choose which bus driver
they want to have attached by offering or not offering that method.

Of course, there will need to be a generic OFW PCI-PCI bridge driver
that adds this method, but it's needed anyway to override the standard
interrupt routing method.

	- Thomas

-- 
Thomas Moestl <t.moestl_at_tu-bs.de>	http://www.tu-bs.de/~y0015675/
              <tmm_at_FreeBSD.org>		http://people.FreeBSD.org/~tmm/
PGP fingerprint: 1C97 A604 2BD0 E492 51D0  9C0F 1FE6 4F1D 419C 776C