"Bradley D. LaRonde" wrote: > > ----- Original Message ----- > From: "Jun Sun" <jsun@mvista.com> > To: "Bradley D. LaRonde" <brad@ltc.com> > Cc: <linux-mips@oss.sgi.com>; <linux-mips-kernel@lists.sourceforge.net> > Sent: Monday, October 29, 2001 5:38 PM > Subject: [Linux-mips-kernel]Re: PATCH: pci_auto bridge support > > > "Bradley D. LaRonde" wrote: > > > > > > I considered that, but since only this small chuck of run-once surrogate > > > bios autoconfig code needs to know, I figured better keep it separate. > > > > > > > I would vote to put it inside the hose structure: > > > > . It makes a workaround look like a real fix. :-) > > > > . In other implementations of pci_auto, hose is the private sys data of a > pci > > dev. Having a bus number inside is very useful (e.g., pci_ops can tell > whether > > it is type0 of type1 configuration based on the bus number rather than a > shaky > > NULL parent bus pointer). In the future, all pci_auto should be combined > into > > the pci driver. So that is probably the right direction to go. > > > > I think hose may evolve to be the data structure that represents the > topology > > of PCI buses. It should have more uses in the future (e.g., the standard > IRQ > > routing across PCI-PCI bridges). > > Isn't the bus topology already adequately represented in the pci_dev and > pci_channel structures? > Not really. For example, we don't know which bus is the sub-bus of which, directly, and how their address space translate into each other. Those data structures are needed when we start to support dynamically mapped and/or arbitrarily mapped PCI memory spaces. > I look at the pci autoconfig stuff as a bios replacement. The fact that we > can use some of the same structures and functions to help us implement it is > a bonus, but not a mandate to mess with the existing model. > That is a right point. I might be too far ahead of myself. :-) > Isn't Linux already handling PCI-PCI bridges and multiple PCI channles fine > already, or has our autoconfig code exposed some existing non-arch-specific > weakness? > I think on PCs, P2P still largely depends on BIOS. (Correct me if I am wrong). There are some post-scan_bus() mechanism to setup P2P bridges. I have not looked into it closely. Jun
