Paul Mackerras writes:
> Dave Airlie writes:
>
> > The changes to types need to clarify what exactly breaks where, I'm not as
> > worried about the interactions between X and Mesa as I am about old
> > Xs and new kernels...
>
> And in context, this comes down to the expectations of existing 64-bit
> X servers and DRI clients on 64-bit kernels with respect to how map
> handles and mmap offsets can be generated and used. I know people are
> currently using 64-bit X servers and DRI clients on x86_64 machines at
> least. I'm pretty sure that userspace currently expects to be able to
> use framebuffer and register physical addresses as the offset in an
> mmap on /dev/dri/card0, and to be able to add an offset to a map
> handle for an AGP mapping and use that as an offset for mmap. At
> least the radeon driver does this IIRC.
If there was such a case I must have missed it.
The only driver where I came across something like this was in
the MGA driver. So I made sure that values that fit into 32bit
remained unchanged if possible.
At the same time I fixed the driver code to obtain the address
from some different source - which was entirely possible.
Also 64bit offsets that don't fit into 32bit won't do you any good
in 32bit as you cannot mmap() them.
>
> And you are right, if we make an incompatible change to the
> user/kernel ABI in the middle of a stable kernel series, people will
> scream, and rightly so.
>
That's not my plan.
Egbert.
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