Re: [Dri-devel] Backwards compatibility status

[jhartmann <jha...@am...>]

Keith Whitwell wrote:

> Jeff, Rik, Others,
>
> Can you please post a description of what the backwards compatibility kernel
> code changes are, how they work, what developers are expected to do to keep
> them working?
>

Here is a quick rundown of how the infrastructure works:
During Xserver startup the Xserver passes an ioctl to the kernel which requests
what version the Xserver and OGL driver expect.

The kernel has a table of file operations pointers indexed by version number, and
if the version number passed into the kernel matches one of the elements in the
list it resets the file operations pointer to the one in the table.

Each driver needs to have this expanded so that it has the 4.1 version and the
mesa-3-5 version.

So basically the infrastructure is there, but not the driver specific bits.  You
will need to create multiple ioctl tables, each with the ioctls for the specific
version.  None of the drivers are completed at this time.  The mga and i810
drivers should be quite easy to finish, but the radeon and r128 drivers on the
mesa 3-5 branch are out of sync with the trunk and will probably take some more
work.  If you wanted to  help me out getting the radeon (its badly out of sync)
closer to the trunk version would help out alot.  Its likely that I will be
taking a trip over the weekend, but I can look at finishing this work after that.

>
> Has this code/technique been ported to the 3.5 branch?  Has that been examined
> for feasibility?
>

What is complete is currently living on the mesa 3.5 branch.

-Jeff