On Wed, 30 Jan 2002, Keith Whitwell wrote:
> Vladimir Dergachev wrote:
> >
> > On Wed, 30 Jan 2002, Daryll Strauss wrote:
> >
> > > On Wed, Jan 30, 2002 at 03:15:53PM -0500, Vladimir Dergachev wrote:
> > > > I completely agree with you.. but I did not give you details :))
> > > >
> > > > What happens is that if you try to use older drm driver with GATOS 2d
> > > > driver the GATOS driver will notice and complain. But if you use GATOS drm
> > > > driver with older 4.2.0 2d driver you will get a lockup.
> > > >
> > > > The reason is that the changes involve programming Radeon's memory
> > > > controller to place AGP aperture after the end of the framebuffer and not
> > > > at the start of PCI space as it is done currently. Both 2d driver and drm
> > > > driver have to agree on this - which is why a bump in major version is
> > > > necessary.
> > > >
> > > > The reason I did not do it is that the mesa driver checks major version as
> > > > well. Hence it will complain if it is bumped. Since I did not want to open
> > > > a new CVS module just for changing version in mesa driver I decided to go
> > > > the "slightly" broken way under assumption that few people with install
> > > > GATOS drm-kernel but will forget to install GATOS 2d driver.
> > > >
> > > > Does this make sense ?
> > >
> > > Sure does, but it sounds like we could change the Mesa drivers to have the
> > > same behavior as the GATOS drivers. If they see version x.y they use the
> > > old offset for AGP and if they see x.y+1 they use the new one. This
> > > would be much better than bumping the major version number.
> > >
> > > I may be glossing over details, in fact I probably am, but putting some
> > > effort into this is probably required if we want to be good Linux citizens.
> >
> > That's a good idea.. Except that it wont' work. Mesa driver is distributed
> > with XFree86 anyway, so when GATOS patch gets merged in everything will
> > work ok. The problem is that I don't know how drm driver can check the
> > version of 2d driver that attempts to initialize it - if you know how
> > please let me know. Without this, first thing after we include mew drm
> > driver into Linux kernel we'll have people downloading it and getting a
> > lockup with 4.2.0 or earlier.
>
> It won't be included if it bumps the major number. You need to come up with a
> way to do this so that old clients *just work*, and new ones do something
> special to access new functionality.
>
> I'd also be wary of assuming that people have the same versions of 2d and 3d
> drivers installed.
The assumption was only made for experimental GATOS drivers. It is a
practical one. More people come and ask: "I upgraded to GATOS driver and
DRI won't work anymore !" Answer: RTFM, upgrade drm driver.
Vladimir Dergachev
>
> Keith
>
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