On Tue, Mar 12, 2019 at 5:10 PM Jerome Glisse <jglisse@xxxxxxxxxx> wrote: > > On Tue, Mar 12, 2019 at 02:52:14PM -0700, Andrew Morton wrote: > > On Tue, 12 Mar 2019 12:30:52 -0700 Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > > > > > On Tue, Mar 12, 2019 at 12:06 PM Jerome Glisse <jglisse@xxxxxxxxxx> wrote: > > > > On Tue, Mar 12, 2019 at 09:06:12AM -0700, Dan Williams wrote: > > > > > On Tue, Mar 12, 2019 at 8:26 AM Jerome Glisse <jglisse@xxxxxxxxxx> wrote: > > > [..] > > > > > > Spirit of the rule is better than blind application of rule. > > > > > > > > > > Again, I fail to see why HMM is suddenly unable to make forward > > > > > progress when the infrastructure that came before it was merged with > > > > > consumers in the same development cycle. > > > > > > > > > > A gate to upstream merge is about the only lever a reviewer has to > > > > > push for change, and these requests to uncouple the consumer only > > > > > serve to weaken that review tool in my mind. > > > > > > > > Well let just agree to disagree and leave it at that and stop > > > > wasting each other time > > > > > > I'm fine to continue this discussion if you are. Please be specific > > > about where we disagree and what aspect of the proposed rules about > > > merge staging are either acceptable, painful-but-doable, or > > > show-stoppers. Do you agree that HMM is doing something novel with > > > merge staging, am I off base there? > > > > You're correct. We chose to go this way because the HMM code is so > > large and all-over-the-place that developing it in a standalone tree > > seemed impractical - better to feed it into mainline piecewise. > > > > This decision very much assumed that HMM users would definitely be > > merged, and that it would happen soon. I was skeptical for a long time > > and was eventually persuaded by quite a few conversations with various > > architecture and driver maintainers indicating that these HMM users > > would be forthcoming. > > > > In retrospect, the arrival of HMM clients took quite a lot longer than > > was anticipated and I'm not sure that all of the anticipated usage > > sites will actually be using it. I wish I'd kept records of > > who-said-what, but I didn't and the info is now all rather dissipated. > > > > So the plan didn't really work out as hoped. Lesson learned, I would > > now very much prefer that new HMM feature work's changelogs include > > links to the driver patchsets which will be using those features and > > acks and review input from the developers of those driver patchsets. > > This is what i am doing now and this patchset falls into that. I did > post the ODP and nouveau bits to use the 2 new functions (dma map and > unmap). I expect to merge both ODP and nouveau bits for that during > the next merge window. > > Also with 5.1 everything that is upstream is use by nouveau at least. > They are posted patches to use HMM for AMD, Intel, Radeon, ODP, PPC. > Some are going through several revisions so i do not know exactly when > each will make it upstream but i keep working on all this. > > So the guideline we agree on: > - no new infrastructure without user > - device driver maintainer for which new infrastructure is done > must either sign off or review of explicitly say that they want > the feature I do not expect all driver maintainer will have > the bandwidth to do proper review of the mm part of the infra- > structure and it would not be fair to ask that from them. They > can still provide feedback on the API expose to the device > driver. > - driver bits must be posted at the same time as the new infra- > structure even if they target the next release cycle to avoid > inter-tree dependency > - driver bits must be merge as soon as possible What about EXPORT_SYMBOL_GPL? > > Thing we do not agree on: > - If driver bits miss for any reason the +1 target directly > revert the new infra-structure. I think it should not be black > and white and the reasons why the driver bit missed the merge > window should be taken into account. If the feature is still > wanted and the driver bits missed the window for simple reasons > then it means that we push everything by 2 release ie the > revert is done in +1 then we reupload the infra-structure in > +2 and finaly repush the driver bit in +3 so we loose 1 cycle. I think that pain is reasonable. > Hence why i would rather that the revert would only happen if > it is clear that the infrastructure is not ready or can not > be use in timely (over couple kernel release) fashion by any > drivers. This seems too generous to me, but in the interest of moving this discussion forward let's cross that bridge if/when it happens. Hopefully the threat of this debate recurring means consumers put in the due diligence to get things merged at infrastructure + 1 time.
