[Mesa-dev] [PATCH] i965: Replace structs with bit-shifting for Gen7 SURFACE_STATE entries.

[Ian Romanick]

On 12/29/2012 04:48 PM, Kenneth Graunke wrote:
> On 12/29/2012 02:38 PM, Ben Widawsky wrote:
>> Anyway, we all agree it's a mess, and I just wanted to point out that
>> this patch is the nail in the coffin. Maybe you should CC the
>> maintainers for the other projects which depend on this?
>
> The nail in the coffin of what, exactly?  intel-gpu-tools has code to
> deal with Gen7 surface states.  I'm not taking that away, and it will
> continue to work.  Nobody is being forced to do anything here.
>
> Also, the only user of struct gen7_surface_state in intel-gpu-tools is
> rendercopy_gen7.c, and is exactly one 40 line function.  That's a
> trivial amount of code.  It could be updated in less time than it took
> to send these emails.
>
> SNA and UXA both have non-trivial uses of gen7_surface_state, but
> consider this:
>
> $ diff -u xf86-video-intel/src/brw_structs.h
> mesa/src/mesa/drivers/dri/i965/brw_structs.h | diffstat
>
>   brw_structs.h | 2517
> ++++++++++++++++++++++++++--------------------------------
>   1 file changed, 1171 insertions(+), 1346 deletions(-)
>
> That tells me: these two files have diverged so significantly that
> they're no longer the same.  And this is before applying my patch.
> There's no way you could simply copy one over the other.
>
> So I don't see how my patch in any way influences the status quo.
>
> One could argue that, for long term maintainability, we should share
> more code between Mesa/IGT/DDX/VAAPI.  We could try and find a solution
> involving a shared library.  We could also explicitly mark that certain
> components should only be edited in repo/project X, and copied from
> there, to avoid divergence.  But each of those comes with a cost and
> various trade-offs, which is why we've continued to punt on finding a
> solution...

It seems like the right solution is to have an "upstream" project that 
generates the header files directly from the bspec.  Then all of the 
various projects can just pull headers from that project.  That project 
could be an existing one or a new one.