Re: [Xpert]RE: [Dri-devel] Re: [GATOS]Re: Bugfix for br0ken DMA onr128 andpossibly radeonDMA functions

[Jens O. <je...@tu...>]

Vladimir Dergachev wrote:
> 
> On Wed, 30 Jan 2002, Jens Owen wrote:
> 
> > Vladimir Dergachev wrote:
> >
> > > Also, I can make drm driver work nice with older 2d drivers - as soon as
> > > someone will show me a way to tell the version of the 2d driver that is
> > > accessing the drm driver.
> >
> > How about using a new set of IOCTL numbers for the new interface--then
> > you'll know whether you have an old or new driver accessing it.
> >
> 
> Jens, it is not a new interface. It is simply a matter of moving AGP and
> framebuffer apertures within cards internal address space. If it is moved
> the buffers (texture, ring buffer, indirect, etc)  need to have their
> addresses adjusted. (that was the place where documentation was wrong..
> it named those fields as "offsets" but they are absolute addresses). Once
> it is setup and the buffer addresses are ok everything goes in as before.
> But if any component gets the wrong idea and tells the card "go get a texture
> from the wrong place" it all locks up.
> 
> To reiterate it is simply a matter of initializing the card.
> 
> The problem arises from the fact that initialization is done both in 2d
> driver and drm driver. DRM initializes the ring buffer and 2d driver sets up
> framebuffer and passes down various buffers - texture, stencil, depth,
> etc. If either is wrong lockup results.

Vladimir,

If any of the assumptions change, including assumptions about
initialization, then you have to consider this a new interface.  Can you
support your new interface and the old interface simultaneously, or will
moving these regions for new drivers REQUIRE they also be moved for old
ones?

If you can support the new and old style mappings, then you have two
options to maintain compatability.  You can go for a whole new set of
IOCTL's--or you can follow Keith's suggestion of looking for an
indication you are dealing with a new driver and then reuse the old
IOCTL's.  The indication can be a single new IOCTL--that tells the DRM
module you have a NEW style driver; and all subsequent DRM requests by
that driver should use the new interface instead of the old one.  If the
IOCLT is not received the old interface should be used.

Vladmir, if for some reason we are not addressing your concern--please
try to rephrase your question and restate some of your assumptions.  I
feel like we're going in circles here.

Regards,
Jens

--                             /\
         Jens Owen            /  \/\ _    
  je...@tu...  /    \ \ \   Steamboat Springs, Colorado