Am 20.11.11 09:46, schrieb Marc Balmer: > The X.Org xf86-video-geode driver, written form AMD Geode CPUs with > graphics chips (e.g. some PC Engines ALIX boards), needs to access some > MSRs (model specific registers) on the AMD Geode CPU at runtime to set > the resolution etc. > > On Linux this is done by opening a special file under /dev, then > lseeking to the "right position" and writing to the file. On BSD, or > OpenBSD to be specific, a different approach had been choosen: I wrote > a small driver, amdmsr(4) (which btw autoconfigures and attaches only on > AMD Geode CPUs) which allows access to the MSRs via ioctl(2) calls. > xf86-video-geode driver supports this upstream. > > Since I (again) have a need for small devce running X, I want to add > amdmsr(4) to src/ and xf86-video-geode to xsrc/. > > Doing it this way will also keep the xf86-video-geode driver > maintainable, since it's compatible with the other BSD that uses this > technique.
Here is a link to the manual page: http://www.openbsd.org/cgi-bin/man.cgi?query=amdmsr&apropos=0&sektion=0&manpath=OpenBSD+Current&arch=i386&format=html And here to the actual implementation in OpenBSD: http://www.openbsd.org/cgi-bin/cvsweb/~checkout~/src/sys/arch/i386/i386/amdmsr.c?rev=1.9;content-type=text%2Fplain
