On Wed, May 24, 2017 at 03:37:35PM +0800, Shawn Lin wrote: > If not getting domain number from DT, the domain number will > keep increasing once doing unbind/bind RC drivers. This could > introduce pointless tree view of lspci as shows below: > > -+-[0001:00]---00.0-[01]----00.0 > \-[0000:00]- > > The more test we do, the lengthier it would be. The more serious > issue is that if attaching two hierarchies for two different domains > belonging to two root bridges, so when doing unbind/bind test for one > of them and keep the other, then the domain number would finally > overflow and make the two hierarchies of devices share the some domain > number but actually they shouldn't. So it looks like we need to invent > a new indexing ID mechanism to manage domain number. This patch > introduces idr to achieve our purpose. > > Cc: Brian Norris <briannorris@xxxxxxxxxxxx> > Cc: Jeffy Chen <jeffy.chen@xxxxxxxxxxxxxx> > Signed-off-by: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx> > > --- > > Changes in v4: > - make domain_nr depends on CONFIG_PCI_DOMAINS instead of > CONFIG_PCI_DOMAINS_GENERIC.(reported by Kbuild Robot) I'm confused about why you posted this v4. It addresses a kbuild issue, but not any of the questions from my review of v3, so reviewing v4 would be a waste of my time. But since we're here, my naive suggestion: >> 1) If we're using ACPI, every host bridge must have a _SEG method, >> and it supplies the domain. We ignore any bridge without _SEG. >> >> 2) If we're using DT, every host bridge must supply >> "linux,pci-domain", and it supplies the domain. We ignore any >> bridge without "linux,pci-domain". >> >> 3) Otherwise, we always use IDA. was *too* simplistic. _SEG is optional. If it's missing we default to domain 0. The point is that we can't mix the IDA with either the ACPI or DT info. I think for ACPI it should be easy: if _SEG exists, we use that. If _SEG doesn't exist, the spec says we that bridge is in domain 0. So I think we should never use IDA if we're using ACPI. For DT, I think we can't use IDA if *any* bridge uses "linux,pci-domain", because there's no way to allocate a specified domain from the IDA. Of course, we see the bridges one at a time, so we don't know ahead of time whether any uses "linux,pci-domain". I think that means we have to decide when we see the very first host bridge which strategy to use. If the first host bridge has "linux,pci-domain", we use that, and if future host bridges don't supply "linux,pci-domain", we probably have to ignore the whole bridge. If the first host bridge doesn't have "linux,pci-domain", we use IDA, and we probably have to ignore any future bridges that *do* have "linux,pci-domain". So it seems like "linux,pci-domain" is basically an all-or-none proposition. Bjorn
