On Tue, Nov 18, 2014 at 12:57 AM, Jamet, Michael <michael.jamet@xxxxxxxxx> wrote: >> -----Original Message----- >> From: Bjorn Helgaas [mailto:bhelgaas@xxxxxxxxxx] >> Sent: Wednesday, November 12, 2014 19:29 >> To: Jamet, Michael >> Cc: linux-pci@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Levy, Amir >> (Jer); Alloun, Dan; Rafael Wysocki; Andreas Noever >> Subject: Re: [PATCH] pci: support Thunderbolt requirements for I/O >> resources. >> >> [+cc Rafael, Andreas] >> >> On Wed, Nov 12, 2014 at 7:52 PM, Michael Jamet >> <michael.jamet@xxxxxxxxx> wrote: >> > Every Thunderbolt-based devices or Thunderbolt-connected devices >> > should not allocate PCI I/O resources per Thunderbolt specs. >> >> Please include a pointer to those specs in the changelog. >> > > Unfortunately these specs are not publically available. > >> > On a Thunderbolt PC, BIOS is responsible to allocate IO resources. >> > Kernel shouldn't allocate the PCI I/O resources as it interferes with >> > BIOS operation. >> > Doing this may cause the devices in the Thunderbolt chain not being >> > detected or added, or worse to stuck the Thunderbolt Host controller. >> >> These new kernel/firmware coordination requirements need to be >> documented. If they're already part of a PCIe ECN or PCI firmware spec, just >> provide a pointer. >> > > Same, this refers to same specs. > >> > To prevent this, we detect a chain contains a Thunderbolt device by >> > checking the Thunderbolt PCI device id. >> >> I'm really not happy about checking a list of device IDs to identify >> Thunderbolt devices. Surely there's a better way, because a list like this has >> to be updated regularly. >> >> Bjorn >> > > This was also discussed internally and the only way to identify Thunderbolt devices is to check the device IDs. > As you said, this will require us to maintain and keep the list up-to-date as we deliver new devices. I don't really see how this can work. You're asking me to put changes based on a secret spec into generic code that is used on every machine with PCI. I have no way to maintain something like that. This seems like a major screw up in the design and documentation of Thunderbolt. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
