On Tue, Oct 15, 2019 at 01:55:41PM -0700, Rodrigo Vivi wrote:

On Tue, Oct 15, 2019 at 04:16:00AM +1000, Dave Airlie wrote:

...

I've kicked this around in my head over the past few weeks but wanted to get some feedback on whether it's a good idea or what impact it might have that I haven't considered.

We are getting requests via both amdgpu/amdkfd and i915 for new user APIs for userspace drivers that throw code over the wall instead of being open source developed projects, but we are also seeing it for android drivers and kms properties, and we had that i915 crappy crtc background thing that was for Chrome but Chrome didn't want it.

Now this presents a couple of issues:

a) these projects don't seem to that good at following our development guidelines, avoid developing userspace features in parallel in the open and having good development implementations before submitting upstream.

b) these projects don't have experienced userspace developers reviewing their kernel uapis. One big advantage of adding uapis with mesa developers is they have a lot of experience in the area as well.

It's leading me to think I want to just stop all uapi submissions via driver trees, and instead mandate that all driver uapi changes are sent in separate git pull requests to dri-devel, I'd try (with some help) to catch all uapi modifications in normal trees, and refuse pulls that modified uapi.

I truly see your reass

I truly see your reasons....

(and I can't even blame an auto-corrector... sorry)

and a separated pull request would even give more visibility to the UAPI changes for everyone. My only concern would be the flow of merging this on different repositories, etc...

So I'd prefer if we could keep on the simplest side.

...

At least I'm considered writing the script and refusing and pulls that have a uapi change that doesn't contain a link to the userspace changes required for it in a public developed repo.

This is a great idea.

Probably better if we could enforce that on "dim" so we couldn't even merge a uapi without a link.

Would you consider a different tag for that:

UAPI: https://gitlab.../code.c

"Reference:" should be enough, but that could very easily bypass any script and a new tag would make the changes even more visible in a way that the separate pull request wouldn't be needed.

...

Thoughts?

Dave. _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel

---

dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel

On Wed, Oct 16, 2019 at 10:28 AM Matt Roper matthew.d.roper@intel.com wrote:

On Tue, Oct 15, 2019 at 04:16:00AM +1000, Dave Airlie wrote:

...

I've kicked this around in my head over the past few weeks but wanted to get some feedback on whether it's a good idea or what impact it might have that I haven't considered.

We are getting requests via both amdgpu/amdkfd and i915 for new user APIs for userspace drivers that throw code over the wall instead of being open source developed projects, but we are also seeing it for android drivers and kms properties, and we had that i915 crappy crtc background thing that was for Chrome but Chrome didn't want it.

Having submitted "that i915 crappy crtc background thing" it's unclear to me what you're trying to say here. If you're trying to claim that this was "thrown over the wall" or that there was an attempt to try to sneak this work in under the radar and circumvent uapi policy then you're way off track and you probably need to review the (long) history of this feature. We've very religiously followed both the spirit and the letter of your upstream uapi policy with regards to that feature and taken great care to ensure it would *not* land upstream without an actual opensource userspace consumer. There was some confusion recently about how ChromeOS was/wasn't using this interface, but the Google guys helped clear that up, and the kernel changes have now returned to their holding pattern and will not go upstream unless new userspace emerges. To refresh your memory on the history:

• The proposed interface was originally posted in 2015/2016 as an FYI to find out if any opensource userspace projects might have a use for this functionality (we already had the patches written since there's non-opensource software that requires it). The cover letters at the time clearly stated that it should not be merged upstream since there was no userspace:

   "Note that this series isn't mergeable yet since we don't (yet)
   have an open source userspace that can make use of it"
   (https://lists.freedesktop.org/archives/intel-gfx/2016-February/087382.html)
  
  

• About 2.5 years later there was suddenly interest expressed both from people involved in Weston and people involved in ChromeOS, and they independently asked for refreshed kernel patches. When the refreshed patches were posted they again included a disclaimer that we needed proper userspace before it could land:

   "As always, we'll still need the patches for at least one of
   those projects to get posted (and reviewed) somewhere public
   before we actually merge these kernel patches."
   (https://lists.freedesktop.org/archives/intel-gfx/2018-October/178202.html)
  
  

• The Weston effort apparently fizzled out, but at the beginning of 2019 we were directed to some patches to the ChromeOS ozone layer (https://chromium-review.googlesource.com/c/chromium/src/+/1278858) that utilized the interface. I'm not at all familiar with the ChromeOS userspace stack, but since the Ozone code was reviewed by non-Intel folks and shows as 'merged' that sounded like a legitimate open source userspace consumer. From that point on the Chromium review links were clearly advertised in the cover letter each time the series was respun so that it would be very clear what the expected userspace was and so any concerns could be raised.

• Daniele and Sean from Google recently brought it to our attention that even though that ozone code made use of the background color property, the ozone interfaces themselves don't get used at higher levels of the ChromeOS stack (and had probably been merged to the ozone layer in error).

Yes I think we (at Google) more or less all assumed that someone else was going to consume the ozone API (at least that's what I did). And because everyone assumed someone else might make use of it, that code ended up landing. I am sorry about that; we'll try to be more careful in the future. As you say the ozone code doesn't provide any feature in itself, it's just plumbing. Obviously a feature on top didn't materialize.

The exact process to fix this isn't really relevant to me, but I think maybe we should have more open discussions when new features like this happen. Ask ourselves "Who will make use of this feature?" and check with that person seems like a good start. At least then, we have a contact point to ask further questions. Maybe through that process we would find that this is just ozone code, and there is no consumer on top. Or we can dig into exactly what's needed to allow shaping the APIs.

Best, Stéphane

Once they helped us understand that the properties wouldn't ultimately be utilized in a meaningful way with a real ChromeOS setup today, we put a halt to the upstreaming effort:

    "Hmm, in that case it sounds like we probably don't actually
    have enough userspace support yet to justify merging the kernel
    changes at this time."
    (https://lists.freedesktop.org/archives/dri-devel/2019-October/239436.html)

So long story short, we've been very transparent about what's going on with this feature for the whole ~4 years it's been floating around. I would hope that you, as DRM maintainer, would have spoken up at some point if you felt there was something else that needed to be handled differently. No code for this api has ever landed in any of the driver trees, so I'm not sure why you called out this work in an email proposing a change to uapi pull requests.

...

Now this presents a couple of issues:

a) these projects don't seem to that good at following our development guidelines, avoid developing userspace features in parallel in the open and having good development implementations before submitting upstream.

b) these projects don't have experienced userspace developers reviewing their kernel uapis. One big advantage of adding uapis with mesa developers is they have a lot of experience in the area as well.

It's leading me to think I want to just stop all uapi submissions via driver trees, and instead mandate that all driver uapi changes are sent in separate git pull requests to dri-devel, I'd try (with some help) to catch all uapi modifications in normal trees, and refuse pulls that modified uapi.

At least I'm considered writing the script and refusing and pulls that have a uapi change that doesn't contain a link to the userspace changes required for it in a public developed repo.

FWIW, requiring a link to the corresponding userspace in the kernel patch itself and not just the series cover letter seems like a reasonable request to me.

Matt

...

Thoughts?

Dave. _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- Matt Roper Graphics Software Engineer VTT-OSGC Platform Enablement Intel Corporation (916) 356-2795 _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel

On Wed, Oct 16, 2019 at 04:00:25PM -0400, Alex Deucher wrote:

On Mon, Oct 14, 2019 at 2:16 PM Dave Airlie airlied@gmail.com wrote:

...

I've kicked this around in my head over the past few weeks but wanted to get some feedback on whether it's a good idea or what impact it might have that I haven't considered.

We are getting requests via both amdgpu/amdkfd and i915 for new user APIs for userspace drivers that throw code over the wall instead of being open source developed projects, but we are also seeing it for android drivers and kms properties, and we had that i915 crappy crtc background thing that was for Chrome but Chrome didn't want it.

Now this presents a couple of issues:

a) these projects don't seem to that good at following our development guidelines, avoid developing userspace features in parallel in the open and having good development implementations before submitting upstream.

b) these projects don't have experienced userspace developers reviewing their kernel uapis. One big advantage of adding uapis with mesa developers is they have a lot of experience in the area as well.

It's leading me to think I want to just stop all uapi submissions via driver trees, and instead mandate that all driver uapi changes are sent in separate git pull requests to dri-devel, I'd try (with some help) to catch all uapi modifications in normal trees, and refuse pulls that modified uapi.

At least I'm considered writing the script and refusing and pulls that have a uapi change that doesn't contain a link to the userspace changes required for it in a public developed repo.

Thoughts?

This seems like more hassle for questionable benefits. I don't know that mesa is really any better than any other driver teams with respect to UAPI. This just seems like sort of a arbitrary political decision. The people working on mesa have as much of an agenda as those working on other projects. Moreover, especially with the migration to gitlab and MRs, I feel that mesa development has gotten more opaque. Say what you will about mailing lists, but at least you could have a drive by view of what's going on. With MRs, you sort of have to seek out what to review; if stuff is not tagged with something you feel is relevant, you probably won't look at it, so the only people likely to review it are the people involved in writing it in the first place, which would be the same whether it's mesa or some other project. I think all of the projects generally have the best intentions at heart, but for better or worse they just have different development models. In the case of the AMD throw it over the wall stuff, it's not really an anti-open source or community engagement issue, it's more of how to we support several OSes, tons of new products, several custom projects, etc. while leveraging as much shared code as possible. There are ways to make it work, but they are usually a pretty heavy lift that not all teams can make.

I think there's a difference between All Tools Sucks (tm) and the discussions not even being accessible at all. I do agree that generally everyone screws up uapi once in a while, and we seem to overall do a not too shoddy job. So code is probably all ok enough.

But imo long term code is fungible and really doesn't matter much, the important stuff is the people and teams who create it, and all the shared knowledge. That's also were I see the benefit in upstream (for customers and vendors and everyone), we can learn from each another. As an example, I've spent lots of time recently reading amdgpu code and how it's used in userspace. Understanding that without having access to the discussion or being able to ping people on irc and mailing lists would have been impossible - lots of questions where I just plain guessed wrong. For the code-over-wall projects that stuff all simply doesn't exist. It's nigh impossible to figure out whether uapi makes sense or not if you can't see all the tradeoffs and discussions that influenced it and why.

That's also why I think the separate pull won't help at all, since Dave will still have incomplete information. All he can do with more pulls is roll the die more often, that's not helping.

Now short term "moar hw support" is cool and all that, but long term I do think it's missing the point of upstreaming. It's not that mesa (or any other cross vendor project, we have a bunch of those on the kms side) is better at uapi, it's that it's more open and so _much_ easier to understand how we ended up at a specific place. That's at least my take on all this.

All of that said, I think providing a link to the userspace user of the API is reasonable, but I don't think there have been any egregious cases of badly designed UAPI that were not caught using the existing processes.

Imo the problem isn't the lack of links, but lack of (public) discussions. One idea I toyed around with could be to require uapi review for new uapi by someone outside the wall. That's defacto what we do for everything pushed through cross-vendor userspace anyway, and it would make sure that all the design considerations relevant to the uapi would bubble over the wall too, not just the code. The people and their expertise would still be in hiding, so still far from nirvana, but I think this would at least move things meaningfully. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch

On Thu, Oct 17, 2019 at 4:12 PM Alex Deucher alexdeucher@gmail.com wrote:

On Thu, Oct 17, 2019 at 9:58 AM Daniel Vetter daniel@ffwll.ch wrote:

...

On Wed, Oct 16, 2019 at 04:00:25PM -0400, Alex Deucher wrote:

...

On Mon, Oct 14, 2019 at 2:16 PM Dave Airlie airlied@gmail.com wrote:

...

I've kicked this around in my head over the past few weeks but wanted to get some feedback on whether it's a good idea or what impact it might have that I haven't considered.

We are getting requests via both amdgpu/amdkfd and i915 for new user APIs for userspace drivers that throw code over the wall instead of being open source developed projects, but we are also seeing it for android drivers and kms properties, and we had that i915 crappy crtc background thing that was for Chrome but Chrome didn't want it.

Now this presents a couple of issues:

a) these projects don't seem to that good at following our development guidelines, avoid developing userspace features in parallel in the open and having good development implementations before submitting upstream.

b) these projects don't have experienced userspace developers reviewing their kernel uapis. One big advantage of adding uapis with mesa developers is they have a lot of experience in the area as well.

It's leading me to think I want to just stop all uapi submissions via driver trees, and instead mandate that all driver uapi changes are sent in separate git pull requests to dri-devel, I'd try (with some help) to catch all uapi modifications in normal trees, and refuse pulls that modified uapi.

At least I'm considered writing the script and refusing and pulls that have a uapi change that doesn't contain a link to the userspace changes required for it in a public developed repo.

Thoughts?

This seems like more hassle for questionable benefits. I don't know that mesa is really any better than any other driver teams with respect to UAPI. This just seems like sort of a arbitrary political decision. The people working on mesa have as much of an agenda as those working on other projects. Moreover, especially with the migration to gitlab and MRs, I feel that mesa development has gotten more opaque. Say what you will about mailing lists, but at least you could have a drive by view of what's going on. With MRs, you sort of have to seek out what to review; if stuff is not tagged with something you feel is relevant, you probably won't look at it, so the only people likely to review it are the people involved in writing it in the first place, which would be the same whether it's mesa or some other project. I think all of the projects generally have the best intentions at heart, but for better or worse they just have different development models. In the case of the AMD throw it over the wall stuff, it's not really an anti-open source or community engagement issue, it's more of how to we support several OSes, tons of new products, several custom projects, etc. while leveraging as much shared code as possible. There are ways to make it work, but they are usually a pretty heavy lift that not all teams can make.

I think there's a difference between All Tools Sucks (tm) and the discussions not even being accessible at all. I do agree that generally everyone screws up uapi once in a while, and we seem to overall do a not too shoddy job. So code is probably all ok enough.

But imo long term code is fungible and really doesn't matter much, the important stuff is the people and teams who create it, and all the shared knowledge. That's also were I see the benefit in upstream (for customers and vendors and everyone), we can learn from each another. As an example, I've spent lots of time recently reading amdgpu code and how it's used in userspace. Understanding that without having access to the discussion or being able to ping people on irc and mailing lists would have been impossible - lots of questions where I just plain guessed wrong. For the code-over-wall projects that stuff all simply doesn't exist. It's nigh impossible to figure out whether uapi makes sense or not if you can't see all the tradeoffs and discussions that influenced it and why.

That's also why I think the separate pull won't help at all, since Dave will still have incomplete information. All he can do with more pulls is roll the die more often, that's not helping.

Now short term "moar hw support" is cool and all that, but long term I do think it's missing the point of upstreaming. It's not that mesa (or any other cross vendor project, we have a bunch of those on the kms side) is better at uapi, it's that it's more open and so _much_ easier to understand how we ended up at a specific place. That's at least my take on all this.

Fair points. I guess I should clarify my thinking. I was assuming that the throw it over the wall teams would discuss the interface publicly as a precondition and i.e., provide patches against the throw it over the wall code to show it's usage even if those changes ultimately would get become publicly available via some throw it over the wall update once the interface lands. My point was just that the both mesa and throw it over the wall teams are equally capable of doing good or bad interfaces and it shouldn't matter who develops it as long as you provide reasonable review.

I think the discussions/patches generally happen and so the strict wording of our rules are followed, at least by intel/amd (there's some other stuff in uapi land that was a lot more skitting the edge, on both sides of the edge). But usually by the time things go public, the discussion is about implementation details. And the big questions like whether we're solving the right problem, or in the right place are all long ago decided already. So not really the useful/interesting stuff is discussed in public.

Of course with hw enabling that can't really be avoided, but then once you've fixed the hw design for a new generation the uapi adjustments (new golden reg state, a few more flags perhaps) are all pretty clear and there's not really two fundamentally different ways to do things.

And like I said, I'm not sure how we could actually change much here without just creating useless paperwork to keep everyone busy while still having no real benefit. -Daniel

Alex

...

...

All of that said, I think providing a link to the userspace user of the API is reasonable, but I don't think there have been any egregious cases of badly designed UAPI that were not caught using the existing processes.

Imo the problem isn't the lack of links, but lack of (public) discussions. One idea I toyed around with could be to require uapi review for new uapi by someone outside the wall. That's defacto what we do for everything pushed through cross-vendor userspace anyway, and it would make sure that all the design considerations relevant to the uapi would bubble over the wall too, not just the code. The people and their expertise would still be in hiding, so still far from nirvana, but I think this would at least move things meaningfully.

-Daniel

Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch