[Mesa-dev] GL4.5 or bust...

Emil Velikov emil.l.velikov at gmail.com
Mon May 16 08:43:39 UTC 2016

Hi all,

On 16 May 2016 at 01:32, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
> On Sun, May 15, 2016 at 8:25 PM, Martin Peres <martin.peres at free.fr> wrote:
>> On 16/05/16 02:55, Jason Ekstrand wrote:
>>> On May 15, 2016 2:01 PM, "Martin Peres" <martin.peres at free.fr
>>> <mailto:martin.peres at free.fr>> wrote:
>>> >
>>> > On 15/05/16 23:54, Ilia Mirkin wrote:
>>> >>
>>> >> On Sun, May 15, 2016 at 4:32 PM, Dave Airlie <airlied at gmail.com
>>> >> <mailto:airlied at gmail.com>> wrote:
>>> >>>
>>> >>> So I said this on irc over the weekend and it seemed like we had some
>>> >>> consensus on holding off 12.0 until we could announce 4.5 on some
>>> >>> hardware. This assumes the FP64 stuff is going in at least.
>>> >>>
>>> >>> So I decided to roll out the proposal here, which is that we finish
>>> >>> GL4.5 features off for at least Skylake I think.
>>> >>>
>>> >>> So what is needed/missing: please add as you see fit.
>>> >>>
>>> >>> a) robustness - radeonsi has some bits of this. We need to get
>>> >>> KHR_robustness bits, that I think Kayden has patches started for, and
>>> >>> i965 needs to ensure it uses robust buffer stuff. I don't think this
>>> >>> one in unobtainable.
>>> >>>
>>> >>> b) cull_distance - I merged something, it broke, I'll fix it today,
>>> >>> job done.
>>> >>>
>>> >>> c) enhanced_layouts - So tarceri has posted patches, we know that to
>>> >>> do it properly we probably need to rip up attribute packing and
>>> >>> rewrite it, however if Kayden thinks what tarceri has done is
>>> >>> functional enough for now, we could merge the final pieces and work on
>>> >>> perfection later.
>>> >>>
>>> >>> d) SIMD32 for i965 compute shaders - this is probably the most unknown
>>> >>> to me, curro says he's got some patches, that need to rebase onto FP64
>>> >>> when it lands, assuming he can do that, and reviewers can get on top
>>> >>> of things, and we possibly only enable SIMD32 in the corner cases
>>> >>> initially, it might be possible to get this landed.
>>> >>>
>>> >>> Have I missed anything? Should we go for it?
>>> >>
>>> >> The bugs that get triggered when you expose GL 4.3+ to UE4 games. Some
>>> >> are ours, some are theirs. Someone needs to sign up for this work.
>>> >>
>>> >> Also, I'd like to mention that ES 3.2 is pretty close as well. But
>>> >> probably not close enough to squeeze in here. Ian has started working
>>> >> on the OES_shader_io_blocks bits of it (which IMO shouldn't be too bad
>>> >> for someone who knows what all GLSL allows and what it doesn't), which
>>> >> was the last remaining big chunk. I have preliminary patches for core
>>> >> support of advanced blending, the rest should all be easy.
>>> >>
>>> >>> For radeonsi, I think the only other missing bit is qbo and
>>> >>> clear_texture, which may or may not make it in time.
>>> >>
>>> >> I'm in favor of this plan. Nouveau should be ready for Fermi and
>>> >> Kepler once Samuel's images patches for Fermi land (mostly reviewed,
>>> >> had a couple of nits). Maxwell will be missing tess and images, and
>>> >> it's unlikely that either of those will get done in a reasonable
>>> >> period of time. I think we can just flip robustness on... probably not
>>> >> meeting all the provisions of that spec, but ... meh.
>>> >>
>>> >> That said, we should put a cap on this timewise - if e.g. it becomes
>>> >> clear that SIMD32 will take a long time (I think the biggest potential
>>> >> issue of the batch), we should just cut a release. Maybe a 1 month
>>> >> cap?
>>> >
>>> >
>>> > Yeah, a cap of 1 month delay compared to the initial plan or 1
>>> > week after the driver reaching 4.5 in master, whatever happens
>>> > first.
>>> I agree with a time limit if we're going to do this. Another suggestion
>>> that had been made is to go ahead with the release and then plan to release
>>> mesa 13 as soon as we get 4.5. I'm personally OK with either.
>>> --Jason
>> Let's see if it would prevent some superstitious people from updating :p
>> In any case, I agree with Jason. Mesa is released often-enough and things
>> will get a little buggy as games suddenly start exercising mesa is funny
>> ways. So, let's not rush it out if it cannot reach the quality needed and
>> just release another major version when it is ready.
> Of course the way to discover that games/applications suddenly start
> exercising mesa in funny ways is to do a release... a bit of a catch
> 22, wouldn't you say? I don't think developers and the users of
> mesa-git are really going to be enough to get all the kinks out. And
> the RC period should be sufficient time to fix any major issues that
> pop up.

Let's see if I can summarise:
 - People want to have a release with GL 4.5 capable driver(s)
 - Mesa releasing is on a time based model, not a feature one.
 - Saying "we must get these X things, no release until then, period"
(GL 4.5 or bust) is just plain silly
 - If we amend ^^ to honour some timeline, than we may not reach the
stated goad even with the imposed delay.
 - Parties interested in the original timeline, may miss, are too shy,
etc. to say anything against this last minute change.

How about we do the following:
 - Keep the plan as originally
 - As people are happy that we have 1-2 drivers covering GL version X,
branch off/feature freeze and release a few weeks later.
 - Last but not least - let's try and bring up such discussions
earlier, please ?
If people have missed the earlier emails let me know we can improve on
that. Don't just ignore them and shout at the last minute, please ?

Thank you

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