On Mon, Nov 6, 2023 at 11:25 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > On Mon, Nov 06, 2023 at 11:05:47AM -0800, Eric Pilmore wrote: > > On Mon, Nov 6, 2023 at 5:44 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > > > > I think the list can just be deleted, there's no traffic anymore, and > > > "hotplug" doesn't make any sense anymore as "everything" can be > > > added/removed from a Linux system these days. > > > > > > So can we just remove it? > > > > > > thanks, > > > > > > greg k-h > > > > Hi Greg, > > > > I was curious about your comment regarding "everything". Is it > > possible to dynamically add/remove entire I/O sub-trees on the PCIe > > side? > > It has for decades. Well, PCIe isn't decades old, but this has worked > for PCI systems for decades. > > > In other words, can a PCIe bridge, and all associated > > sub-branches be dynamically added/removed? > > Again, yes, for a very long time. If your hardware supports it. > > > If so, is there special BIOS support required for possibly reserving > > adequate MMIO address space? > > Yes. That's what those types of systems do, this is nothing new at all, > we had this working in Linux in 2002 or so. You need special hardware > to support this, and USB4/Thunderbolt is bringing this for more common > hardware as well. Special MMIO reservation in BIOS is not required if a device in your PCIe tree, such as a Broadcom Gen4 or Gen5 switch device, can reserve address space via "synthetic mode" for missing devices. Matt -- Matthew Dharm Former Maintainer, USB Mass Storage driver for Linux
