On Thu, Jan 04, 2024 at 04:50:14PM +0100, Michal Simek wrote:
On 1/4/24 16:30, Tom Rini wrote:
On Thu, Jan 04, 2024 at 03:45:10PM +0100, Michal Simek wrote:
Hi Tom,
On 1/4/24 14:50, Tom Rini wrote:
On Thu, Jan 04, 2024 at 06:52:32PM +0530, Sumit Garg wrote:
Hi Michal,
On Thu, 4 Jan 2024 at 15:39, Michal Simek michal.simek@amd.com wrote:
On 1/3/24 17:32, Tom Rini wrote: > On Wed, Jan 03, 2024 at 09:19:40AM -0700, Rob Herring wrote: > > On Thu, Dec 28, 2023 at 4:59 AM Sumit Garg sumit.garg@linaro.org wrote: > [snip] > > > +In order to maintain devicetree files sync, U-Boot maintains a Git subtree for > > > +devicetee-rebasing repo as `devicetee-rebasing/` sub-directory. It is regularly > > > +kept updated with every new kernel major release via subtree pull as follows:: > > > > I would suggest dropping "-rebasing" in the u-boot tree. (I wish we > > had in the original repo). I don't think it's relevant. > > > > We're not likely to regenerate the tree, but any clue what 'git > > subtree pull' would do in this case? It could happen if we switched to > > git-filter-repo. > > > > > + > > > + git subtree pull --prefix devicetree-rebasing \ > > > + git://git.kernel.org/pub/scm/linux/kernel/git/devicetree/devicetree-rebasing.git \ > > > + <release-tag> --squash > > > > I'd put this in a script to run. Documentation tends to be not quite > > correct. A script could also be smarter and figure out <release-tag>. > > Since you had mentioned elsewhere moving the kernel scripts/dtc/ to > something using subtree, I do hope to learn some lessons from what you > do there. The first thing is that given the size/nature of the commits, > I had figured I'd be the one doing this as a subtree pull+squash then > push, rather than posting to the ML since it'll be huge and > un-reviewable, but with a note sent off to the ML that people should be > aware the next sync has been done and retest as needed. But Sumit, were > you planning to do some of this instead? The second thing is that if we > move the subtree part in to dts/ instead (where we will still have the > Makefile/Kconfig we have today and then our Makefiles within the > directories, this might get more complex and so really require a script > to keep it from getting error prone?
I played with this series and didn't really have time to dig into subtree mechanics but one thing I see is that when squash and merge happens you can't do simple rebase anymore which is time to time very useful. I see some different rebase strategies and --rebase-merges option but if this is adopted it should be properly described how to rebase u-boot tree which contains some subtrees.
Did you observe any specific difference with respect to subtree merge commits (Tom will likely do those in the beginning of next release cycle) when compared with normal merge commits when Tom pulls in code from different custodians like one example below? The same rebasing rules should apply to both types of merge commits.
commit dffa6d0210f57793f1e4e1e209d91ca5642e4d05 (origin/next) Merge: 2b28c3b871c e266d273114 Author: Tom Rini trini@konsulko.com Date: Mon Jan 1 12:38:15 2024 -0500
Merge tag 'dm-next-1124' ofhttps://source.denx.de/u-boot/custodians/u-boot-dm into next
support propagating supernode properties with bootph schema align bloblist with v0.9 of Firmware Handoff specThere's two cases. The first and uncommon case is that if you want to do something like:
- Branch next
- Add this subtree, do a few subtree updates on it (like my experiment of starting with v6.1-dts and merging up to v6.6-dts)
- Wait a while, have changes happen in next
- Rebase on to current next
It gets painful and odd, but I don't know that this will ever really happen.
The second, common case is:
- Assume "next" already has this subtree + some merge commits in it.
- Make a new local branch.
- Make change in your new local branch.
- This hypothetical "next" branch moves forward with changes
- Rebase your local branch on to this "next" branch
In this case things work as expected. Even if "next" in that case gets a new subtree merge that you need to rebase in.
A third case that I'm not sure if really will happen or is a case where the custodian should rework their tree instead (to drop the subtree merge) is:
- Assume "next" already has this subtree + some merge commits in it.
- Make a new local branch.
- Make a subtree merge+squash in your local branch.
- This hypothetical "next" branch moves forward with changes
- Rebase your local branch on to this "next" branch.
This will then make you try and resolve some conflicts from that subtree merge. But is this a valid use case? Yes, I can see wanting to get a start on testing a dts merge before it happens, but is this a tree which needs to be rebased, or just re-created as needed, if the parent branch moves forward?
Can you explain a bit more your case Michal since it sounded to me like you had a problem that happened rather than a worry about what might happen?
I remember couple of bisects which I was doing and it works fine on the tree till the point you have 2 issues to deal with. It means pretty much you have config change/fix which has to be applied to see second issue.
The normal way what I have done was simply find major version apply that fix and then take the latest tree and rebase latest on the top of it. There were normally not so many conflicts to resolved (or easy to resolve/ignore). Then because the first fix is present all the time bisect is able to help me to find second issue.
If there is subtree update the whole rebase will horribly fail.
I see that Rob and you in DTC case just simply do c&p and create regular commit with all changes inside. From my perspective this is more straightforward to deal with which will handle all cases and it is also proven over that years.
Ah, bisecting. Maybe the (annoying) answer is to turn that merge commit in to a regular commit in the bisect branch? This is a good point, and I need to go and construct a bigger example tree and check around at what happens.
Sure you can do whatever you like. But I expect that at the end if this started to be used you will have subtree for devicetree, dtc, lwip and maybe something else. It means you have to start to keep track where that subtree are and what version is used at what time.
Yes, lwip would be a subtree too, dtc is trickier but I see and agree with your point.
Because dt binding is extending often likely you will need to merge it every Linux release. It means you would have to do it multiple times depends on how many releases you are going over.
Yes, the plan is to re-sync every time our next opens with the kernel release at the time (which maybe needs to be clearer in the docs).
I know that Qemu is using gitmodules that's definitely another option but not sure if better or worse.
Yeah, submodules is harder and we're not going that path.
I can also imagine that companies with SR IR certified firmware would keep downstream version where they want to just take code fixes, DT fixes and devicetree-rebasing tree to make sure that they are still aligned with DT schema. Can you simply just cherry pick that merged commit without any side effect?
Life downstream is always fun. Personally, I would re-run the "git subtree" command rather than cherry-pick from U-Boot itself in that case, but it should be no different than any other commit.
Back to my point. At the end what we need to is to document it properly how to deal with it.
So, here's the test I did. I went back to v2023.10, then added v6.1-dts as a subtree. I rebased v2024.01-rc1 on top of that, added a fake bad commit, synced up subtrees to v6.6, and then rebased the tags along the way to v2024.01-rc6. I then went for a bisect back to the fake bad commit. Everything went fine, git didn't have troubles rebasing things as it went.
But to re-iterate, yes, the policy around when dts and bindings will be resynced needs to be clear and documented. Does that cover it?