[Xorg-driver-geode] FreeBSD patch for xf86-video-geode 2.11.12

[Gaetan Nadon]

On Mon, 2011-11-14 at 07:47 +0200, Mart Raudsepp wrote:

> On P, 2011-11-13 at 21:12 -0500, Gaetan Nadon wrote:
> > On Mon, 2011-11-14 at 03:10 +0200, Martin-Éric Racine wrote: 
> > > 2011/11/14 Gaetan Nadon <memsize at videotron.ca>:
> > > > On Sun, 2011-11-13 at 23:51 +0200, Martin-Éric Racine wrote:
> > > >
> > > > It just occured to me that Marc Balmer once contacted the list with an
> > > > announce that he was maintaining the OpenBSD port of xf86-video-geode.
> > > > Let's see if he can participate in this discussion and provide some of
> > > > the answers. Who knows, he might already have a usable diff to provide
> > > > us with as a starting point. :)
> > > >
> > > >
> > > > Great.
> > > >
> > > > http://www.openbsd.org/i386.html#hardware
> > > >
> > > > Geode listed as being supported.
> > > >
> > > > http://www.openbsd.org/cgi-bin/cvsweb/xenocara/driver/xf86-video-geode/
> > > >
> > > > I could not really see any code changes having been done.
> > > 
> > > Try the diff to these two, for starters:
> > > 
> > > --- xf86-video-geode/src/Makefile.am
> > > +++ OpenBSD/xenocara/driver/xf86-video-geode/src/Makefile.am
> > > 
> > > --- xf86-video-geode/src/geode_msr.c
> > > +++ OpenBSD/xenocara/driver/xf86-video-geode/src/geode_msr.c
> > > 
> > > There's also some interesting changes to *_driver.c and to lx_exa.c as
> > > well. A worrisome number of #ifdef, rather than
> > > autoconf/automake/libtool magic, but it's still a nice start.
> > > 
> > > > on OpenBSD/i386 (32 bit) and not 64 bit which would be OpenBSD/amd64 (Intel
> > > > EMT64 is considered a clone of AMD64). If I see this correctly, the OpenBSD
> > > > geode driver does not run on 64 bit and therefore would not be of a great
> > > > help.
> > > 
> 
> Of course it does not run on 64bit. Geode video driver is for an
> integrated into the Geode CPU graphics functionality, and the Geode CPU
> is a i686 32bit CPU (without some Pentium Pro add-ons to i686 insn), so
> the code would be never executed on a 64bit OS.
> 
> > > It does help us see how OpenBSD dealt with the lack of V4L2 capability
> > > and with finding the MSR on their platform, among other things. That's
> > > a good start for adding BSD support in general.
> > > 
> > I ?think? I have figured out part of it. It is relatively simple.
> > 
> > Geode driver should use AC_SYS_LARGEFILE. It's job is to test the size
> > off_t. If 64, it defines #define _FILE_OFFSET_BITS 64 on system where
> > it can be set. With this being set, lseek will become lseek64 and
> > off_t will become off64_t. This behaviour is described in Linux man
> > page http://linux.die.net/man/3/lseek64. 
> > 
> > The geode_msr.c code should not hard code lseek64 or off64_t as these
> > are not defined by all OS such as FreeBSD. 
> >         ret = lseek64(fd, (off64_t) addr, SEEK_SET);
> > This is what prompted FreeBSD to define lseek64 and off64_t.
> > With this fix, which is trivial to test, FreeBSD will work and so will
> > any platform.
> > 
> > Another thought. Perhaps FreeBSD was a 32 bit version (with 64 bit,
> > durango.c would fail). In this case AC_SYS_LARGEFILE is not needed and
> > we just need to replace lseek64 with lseek. Comes to think of it, it's
> > strange to code lseek64 on code that only compiles on 32 bit OS.
> 
> My understanding is that the primary reason of lseek64 and co existing
> is for supporting large files/descriptors (larger than 4GB) on 32bit
> CPUs correctly.
> That said, I'm not sure how much sense it makes in the context of 32bit
> CPU MSR registers. Maybe /dev/cpu/0/msr is supposed to be accessed with
> largefile routines? Or maybe not.
> 

geode_msr.c defines LARGEFILE64_SOURCE

http://linux.die.net/man/3/lseek64

If I read the man page correctly, one can use #define _FILE_OFFSET_BITS
64 and lseek/off_t and would work the same way, but in a portable way
for FreeBSD as they don't have lseek64 defined.

We can thus benefit from AC_SYS_LARGEFILE as the macro will set-up the
#define _FILE_OFFSET_BITS 64 on the appropriate platforms, now and in
the future.

Does anyone know if geode_msr need to use "large" file descriptor?

> 
> Best,
> Mart Raudsepp
> 
> > It looks like you have found more porting issues, I'd be surprised if
> > there were only one.
> > 
> > > Martin-Éric
> > 
> 
> 


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