Date: Fri, 01 Feb 2008 19:18:38 -0700 From: Scott Long <scottl@samsco.org> To: John Baldwin <jhb@FreeBSD.org> Cc: cvs-src@FreeBSD.org, src-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/dev/pci pci.c Message-ID: <47A3D2FE.1060202@samsco.org> In-Reply-To: <200802012031.m11KV9NZ095246@repoman.freebsd.org> References: <200802012031.m11KV9NZ095246@repoman.freebsd.org>
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John Baldwin wrote: > jhb 2008-02-01 20:31:09 UTC > > FreeBSD src repository > > Modified files: > sys/dev/pci pci.c > Log: > Relax the check for a PCI-express chipset by assuming the system is a > PCI-express chipset (and thus has functional MSI) if there are any > PCI-express devices in the system, not requiring a root port device. > > With PCI-X the chipset detection has to be very conservative because there > are known systems with PCI-X devices that do not appear to have PCI-X > chipsets. However, with PCI-express I'm not sure it is possible to have > a PCI-express device in a system with a non-PCI-express chipset. If we > assume that is the case then this change is valid. It is also required > for at least some PCI-express systems that don't have any devices with > a root port capability (some ICH9 systems). > > MFC after: 1 week > Reported by: jfv > > Revision Changes Path > 1.357 +2 -5 src/sys/dev/pci/pci.c It's certainly possible for a PCI-X device to be plugged into a PCI-only system; PCI-X is backwards compatible at an electrical an protocol level with 3.3V PCI. So yes, you will see PCI-X extcaps on PCI-X cards even if there is no PCI-X bridge. I'm sure there are fun, interesting, and highly obtuse ways to get a PCI-E device onto a system with no PCI-E root complex. I do agree with your implicit statement to not worry about such an edge case, at least not until such an edge case becomes a demonstrated reality. What does worry me is that Intel would release PCI-E chipsets without an advertised root complex. That would seem to blatantly violate the spec. Does Jack have confirmation that this is really the case? If so, what else is being played fast-and-loose with that we should know about? Scott
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