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

[Simon Glass]

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.

>
> BR,
> Maxim.

Regards,
Simon

[1] https://www.atlassian.com/git/tutorials/git-subtree