[Mesa-dev] [PATCH 01/41] glapi: Added ARB_direct_state_access.xml file.
Jason Ekstrand
jason at jlekstrand.net
Fri Jan 23 13:53:34 PST 2015
On Fri, Jan 23, 2015 at 1:46 PM, Emil Velikov <emil.l.velikov at gmail.com>
wrote:
> On 23/01/15 20:51, Jason Ekstrand wrote:
> >
> >
> > On Thu, Jan 22, 2015 at 9:27 AM, Emil Velikov <emil.l.velikov at gmail.com
> > <mailto:emil.l.velikov at gmail.com>> wrote:
> >
> > On 05/01/15 17:45, Laura Ekstrand wrote:
> > > This comment is vague. Do you have a specific recommendation for
> the
> > > code here?
> > >
> > Seems like I'm way too subtle - yes I have a few.
> >
> >
> > 1. Add ARB_direct_state_access to struct gl_extension
> > --- a/src/mesa/main/mtypes.h
> > +++ b/src/mesa/main/mtypes.h
> > @@ -3731,6 +3731,7 @@ struct gl_extensions
> > GLboolean ARB_depth_clamp;
> > GLboolean ARB_depth_texture;
> > GLboolean ARB_derivative_control;
> > + GLboolean ARB_direct_state_access
> > GLboolean ARB_draw_buffers_blend;
> > GLboolean ARB_draw_elements_base_vertex;
> >
> >
> > 2. Use it in the extensions table.
> > --- a/src/mesa/main/extensions.c
> > +++ b/src/mesa/main/extensions.c
> > @@ -103,6 +103,7 @@ static const struct extension extension_table[]
> = {
> > { "GL_ARB_depth_clamp",
> o(ARB_depth_clamp),
> > GL, 2003 },
> > { "GL_ARB_depth_texture",
> > o(ARB_depth_texture), GLL, 2001 },
> > { "GL_ARB_derivative_control",
> > o(ARB_derivative_control), GL, 2014 },
> > + { "GL_ARB_direct_state_access",
> > o(ARB_direct_state_access), GL, 2014 },
> >
> >
> > 3. Make use of if when the spec amends existing behaviour - most of
> the
> > spec text as of section "New Tokens" onwards. Clearly with this
> series
> > you're adding the new entry points(functions) so it does not apply
> > here :)
> >
> >
> > if (foo->Extensions.ARB_direct_state_access) {
> > ....
> > }
> >
> >
> > Pretty much every extension that was added to mesa follows this
> approach
> > so keeping up with traditions is always nice.
> >
> >
> > Yes, and no... We have the table of booleans in gl_extensions so that
> > we can expose different extensions/behavior on different drivers.
> > However, ARB_direct_state_access doesn't actually add new functionality,
> > just new ways of getting at old functionality. We *should* be able to
> > implement it in a driver-agnostic way entirely within core mesa.
> > Therefore, there's no reason to be able to shut it off on a per-driver
> > basis and no reason for the flag in gl_extensions. If we find that, for
> > some reason, we only want to support it in core contexts or that it adds
> > something some drivers can't handle it, then we'll need the flag.
> True, yet the usual approach so far had been:
> 1. add the flag
> 2. enable when/where possible
> 3. evaluate if things can be enabled for everyone
> 4. drop it (replace with dummy_true).
> Why bother ? See below.
>
The "usual approach" is for extensions that add functionality and require
per-driver implementation. This extension is kind of unique in that
*nothing* it adds is per-driver (as far as I know).
> There will be a point where the extension will still be dummy_false, yet
> the amendments to the spec will be applied.
>
What "ammendments to the spec"? Once it gets implemented, we'll turn it on.
> At that point there will be a "few" reports from your QA team and other
> people, that piglit (other) has regressed. Going the usual route will
> save you that, at the cost of having one extra commit worth
> (presumingly) ~50loc.
>
> Hope with ^^ things make (a bit more) sense :)
>
Not really. Right now it's not even 100% implemented, so it needs to be
off for everyone. As far as anyone can tell, it will go directly from
dummy_false to dummy_true. If we do find something in the way of
implementing it that can't be done on some drivers, we can add the flag and
then turn it on per-driver instead of turning it on for everyone. I'm
really not seeing how a per-driver flag will do any good.
--Jason
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