[PATCHv8 00/15] net/lwip: add lwip library for the network stack

[Ilias Apalodimas]

Hi Maxim,

On Wed, 13 Sept 2023 at 10:32, Maxim Uvarov <maxim.uvarov at linaro.org> wrote:
>
>
>
> On Wed, 13 Sept 2023 at 01:27, Simon Glass <sjg at google.com> wrote:
>>
>> Hi Maxim,
>>
>> On Tue, 12 Sept 2023 at 05:42, Maxim Uvarov <maxim.uvarov at linaro.org> wrote:
>> >
>> > On Fri, 8 Sept 2023 at 19:59, Tom Rini <trini at konsulko.com> wrote:
>> >
>> > > On Fri, Sep 08, 2023 at 07:53:05PM +0600, Maxim Uvarov wrote:
>> > >
>> > > > Before apply these patches it  is needed to create lwIP merge into
>> > > U-Boot:
>> > > > git subtree add --prefix net/lwip/lwip-external
>> > > https://git.savannah.nongnu.org/git/lwip.git master --squash
>> > > > or
>> > > > create git submodule, depends how it's more easy to maintain external
>> > > > library.
>> > >
>> > > So, I think we're going to go with subtree.  Please work out how to
>> > > integrate the above in to the build process automatically (and such that
>> > > we can maintain it via upgrades moving forward).
>> > >
>> > > --
>> > > Tom
>> > >
>> >
>> > I did not find a good way to friend git format-patch, git am and subtree.
>> > And now with using subtree I can provide my thoughts, in general I do not
>> > see any big advantages
>> > with maintaining subtree code.
>> >
>> > Problem is that:
>> >
>> > 1. subtree does some root reset. So rebase looks like:
>> > label onto
>> >
>> >
>> >
>> > # Branch acbc0469a49de7055141cc730aa9c728e61b6de2-2
>> >
>> > reset [new root]
>> >
>> > pick acbc0469a4 Squashed 'net/lwip/lwip-external/' content from commit
>> > 84fde1ebbf
>> > label acbc0469a49de7055141cc730aa9c728e61b6de2-2
>> >
>> >
>> >
>> > reset onto
>> >
>> > merge -C ec4a128c8d acbc0469a49de7055141cc730aa9c728e61b6de2-2 # Merge
>> > commit 'acbc0469a49de7055141cc730aa9c728e61b6de2' as
>> > 'net/lwip/lwip-external'
>> > pick 739681a6f5 net/lwip: add doc/develop/net_lwip.rst
>> >
>> > pick f0ecab85e0 net/lwip: integrate lwIP library
>> >
>> > 2. if  --rebase-merges option was not provided to rebase, then rebase will
>> > omit subtree directory and try to apply rebase patches to root directory.
>> > I.e. in current case squashed commit for lwip, will be applied to uboot
>> > root directory instead of ./net/lwip/lwip-external.
>> >
>> > 3. due to broken rebases without --rebase-merges more likely things like
>> > git bisect also will not work.
>> >
>> > 4.  change in subtree code ./net/lwip/lwip-external/../something.c will
>> > create a git commit which looks like a standard U-Boot commit. I.e. path
>> > starts with ./net/lwip/lwip-external/
>>
>> I don't really understand most of the above, but I take it that
>> subtree has some problems...I did find an article about subtree [1]
>>
>> >
>> > 5. lwip maintains code with a mailing list.  So we don't need to push
>> > subtree git somewhere to create a pull request.
>> >
>> > 6. I rechecked the latest edk2 and they use submodules now. (openssl,
>> > libfdt, berkeley-softfloat-3 and others).
>> >
>> > 7. dynamic download also looks horrible for me. I.e. create subtree in
>> > Makefile on compilation process. I think maintaining that will give you a
>> > bunch of problems. I think we should not touch git structure after cloning.
>> >
>> > So what I can here suggest:
>> > 1.  lwip source code is 9.4M.  If we compare all code it will be 564M in
>> > total. So just having 1 commit witn copy of lwip library will work here.
>>
>> So we add a 9.4MB patch for the code we need? I suppose that is OK,
>> although it is much larger than net/ today (0.5MB).
>>
>> What is the churn on lwip? E.g. would it be easy to add a commit every
>> few months to bring in upstream changes?
>>
>> >
>> > or
>> >
>> > 2. use git submodules. Size of the project will be lower.  Submodule will
>> > not allow you to use local changes. I.e. change needs to be merged into the
>> > upstream project and then you can update git HEAD for the submodule.
>>
>> I really don't want to work with a submodule project. I've just had
>> too many problems.
>>
>> >
>> > or
>> >
>> > 3. inside u-boot.git create branch lib-lwip and clone lwip repo there. Then
>> > use git submoule to connect this branch as a folder to the main U-Boot code.
>>
>> It really needs to be properly part of U-Boot.
>>
>
> Ok. Then more likely we don't need all the git history of lwip inside uboot.git. Then the option with a single commit is more preferable.
> Then we can use part 2 of this article, how to  go with standard git commands:
>
> 1.
> <cmd>
> git remote add -f lwip https://git.savannah.nongnu.org/git/lwip.git
> git read-tree --prefix=net/lwip/lwip-external -u lwip/master
> git commit -m "lwip merge sha: xxxx"
> </cmd>
> this will create a git format-patch friendly commit. Then we send it to the mailing list  and apply.
> I hope the mailing list will allow us to send a 7.8 MB patch.
>
>
> Then if for development you need  to pull he history of lwip, you can do it with:
> git pull -s subtree lwip  master --allow-unrelated-histories
> (but I think nobody will need this.)
>
> New update of the lwip net/lwip/lwip-external dir will be done with:
> git pull -s subtree lwip  master --allow-unrelated-histories --squash
> Squash commit also has to be git format-patch friendly.
>
> If you are ok with that proposal I will send v9 with the first patch created with steps above.

We've gone through this before.  The whole purpose of this is not
having to maintain patches.
Simon, instead of "I had problems in the past", can you elaborate a bit more?

Tom said he is fine with subtrees instead of submodules and I know for
a fact EDK2 doesn't have too many issues with submodules.
Their documentation is pretty clear on building and requires

git clone https://github.com/tianocore/edk2.git
cd edk2
git submodule update --init

Perhaps the situation has improved since you had issues?

Thanks
/Ilias
>
> Thanks,
> Maxim.
>
>
>
>
>
>
>>
>> >
>> > BR,
>> > Maxim.
>>
>> Regards,
>> Simon
>>
>> [1] https://www.atlassian.com/git/tutorials/git-subtree