[coreboot] [PATCH] Use a tag for SeaBIOS stable checkouts.

[Peter Stuge]

Stefan Reinauer wrote:
> > Can I ask why you don't want to create a commit for the changes?
> 
> It needs more of git setup in order to use the system (such as the user
> name and email),

That's a point, though it doesn't matter significantly because the
commit would not really be sent to anyone else. (git can still commit
without explicit config, it'll just default to $USER@$(hostname -f)
for the email.)

Require config I agree we must not. But having a commit for the
changes in the git repo is I think something we could consider.
However..


> so I am hesitating to put this constraint on the users for
> something that should not require a commit in the first place.
> It's only a configuration change.

The problem is that we want to do a configuration change, but that
configuration file is being managed by git as part of the sources.

So after the configuration file has change, git expects to be told
what to do with the change, since the file *is* part of the repo.


> > > nor do I want to undo/redo the changes for every build,
> > 
> > Well, but every build can (outside abuild) switch to a different
> > branch. And we need to handle that. (Ie. a user first building with
> > master, then building with stable.)
> 
> I believe that my original code did that, at least it worked in my
> tests.

A file in the working copy being modified blocks most operations in
git because it can't know the intent of the changes, so I'd be
surprised if git pull worked while config.h had uncommitted changes.


> > > nor do I want to re-checkout for every target.
> > 
> > Why not? Note we are talking git checkout now, not git clone.
> 
> No, actually I was talking about git clone. Sorry, I am not quite used
> to all the git nomenclature yet.

No problem. And I agree with this, clone should always just be done
once. And git helps with that.


> In fact git checkout simply failed for me with varying errors.

I can see a couple of reasons why it would. Git doesn't allow a
checkout if it can't tell that the current state of the working copy
will be "easily" reproducable. That of course includes uncommitted
changes, but it would also include having no uncommitted changes, if
the current worktree state is not on a local branch, such as would be
the case after a cycle of checkout origin/master + commit config.h
changes.


> > >  checkout:
> > >         echo "Checking out SeaBIOS $(TAG-y)"
> > > -       test -d seabios && ( cd seabios; git pull ) || \
> > > +       test -d seabios && ( cd seabios; git fetch ) || \
> > 
> > I agree that git fetch should be here, certainly not git pull.
> 
> A fetch alone does not seem to make much sense.

Note "here". The checkout comes just afterwards.


> It will not update the tree when working with the master tag, as
> far as I can tell.

Correct, git fetch will *never* update the worktree. It will however
download new changes from upstream, and they will be available in the
branch origin/master that is created automatically whenever cloning a
repo.


> The idea of master is that you will always get the latest and
> greatest SeaBIOS, so the tree should be updated accordingly, eh,
> fetched and merged.

Not neccessarily merged (git merge or other) because it would mean
that what is in the local work tree has departed from what is
upstream, but more importantly because it makes it awkward to jump
around in the repository (switch between master and stable e.g.)
because what is actually configuration is handled as if it were
source code.


> Let's start with the simple case of us just building a plain image from
> the SeaBIOS git repository without the user changing stuff on top of
> that. Remember, this is just the "simple path". If you want to develop
> SeaBIOS and change it, you can always specify it as external ELF payload
> instead of using this automatism.

Great. I agree with this very much, because it allows us to solve the
particular use case, and then we can also tell people what to do and
not do to keep it working.


> > > -       cd seabios; git checkout $(TAG-y)
> > > +       cd seabios; git checkout -m $(TAG-y)
> > 
> > I don't really like trying to do a merge of local changes here. It
> > will quickly conflict with later development from upstream.
> 
> Well, unless SeaBIOS switches over to a non-checked-in, auto generated
> config.h we will probably have to do this. Do we want to switch SeaBIOS
> over to Kconfig? That would certainly solve the issue, and allow to
> specify a default config, as well as user or coreboot specific changes
> to the configuration.

Actually Marc Bertens is working on this as we speak over on the
SeaBIOS mailing list, but it would not be neccessary to go all the
way there to solve the problem.

Renaming config.h to config.h.in and having a configuration step be
part of the build (it could be called from Makefile, so still only
need to run make for default settings) that generates config.h would
work. In that case, Git would be told to always ignore config.h, and
it would never matter if it was changed by coreboot build.

It essentially does the same as my COMMONCFLAGS idea, just stores the
actual settings in a file, which I think has clear benefits.


> I think that's out of focus, as described above. However, we need to
> configure SeaBIOS to actually work on top of coreboot, and that requires
> automatically doing "local changes" due to the way the code works currently.

Right. We will need to change SeaBIOS, but not very much. I think my
patches might be the minimal solution, but nicer and only slightly
larger would be to have a config.h.in/config.h dance, where the major
benefit is that actual used configuration gets stored on the
filesystem and not just in the environment.


> > I think merging is always the wrong thing to do, because it will make
> > a mess of the repo and what the user has configured is exclusively
> > one of the tags we offer, so that is what they should always get.
> 
> I think it's quite incredible that we can not update the version of
> SeaBIOS automatically because we enabled it to build with coreboot
> and serial console support. We need to fix this constraint.

See above for an attempt at explanation. The issue is that we have
made changes to the source code, without telling git how it should
treat those changes. We can give git pretty much any instruction we
want, but we do need to give it instruction. Does that make sense? :)


> > Subject: [PATCH 1/2] Allow initial COMMONCFLAGS to be set from the make command line
> 
> The patch will probably allow CFLAGS like -O2 be overwritten by -Os?
> 
> I think COMMONCFLAGS is not something the user should set. The commonly
> used notion would suggest the user set CFLAGS instead.

I don't care at all about the actual names of variables used, the
point was just to suggest using environment for configuration, since
it should not really be part of the (version controlled) source code.
However, I think a configuration pass would be far superior.


> > Subject: [PATCH 2/2] Allow override of CONFIG_COREBOOT CONFIG_DEBUG_SERIAL CONFIG_VGAHOOKS
> 
> Should other flags be exported as well? All of them? 

Maybe. I just did the ones that were touched by coreboot. I thought
that others could be added as the need comes up.


> I like the approach, and it is the right thing to do, not changing the
> code. But it also adds "logic" to the config file, which is a bit eerie.

Well, yes, and config becomes volatile, which is my main objection.


> >  checkout:
> >  	echo "Checking out SeaBIOS $(TAG-y)"
> > -	test -d seabios && ( cd seabios; git pull ) || \
> > +	test -d seabios && ( cd seabios; git fetch ) || \
> 
> will this actually make sure I am running the latest version when
> selecting master?

No, but the git checkout command that you cut away will. :)


> If so, I think we should go with this until we have a better solution.
> It will require the above config.h change to be checked into a new
> stable release first though, and our stable release version in
> payloads/external/SeaBIOS/Makefile.inc should be pushed to that
> version then.

Right, this problem stretches across both SeaBIOS and coreboot, so we
should make sure the solution is one we actually like. :)


Kevin O'Connor wrote:
> > > > +       test -d seabios && ( cd seabios; git fetch ) || \
> > > 
> > > I agree that git fetch should be here, certainly not git pull.
> > 
> > A fetch alone does not seem to make much sense. It will not update the
> > tree when working with the master tag, as far as I can tell. The idea of
> > master is that you will always get the latest and greatest SeaBIOS, so 
> > the tree should be updated accordingly, eh, fetched and merged.
> 
> The fetch should be okay, because the patch also changes the tag from
> "master" to "origin/master".

Ah, yeah, git fetch could certainly become git fetch origin to become
perfectly clear. It will fetch all branches, both stable and master.


> The real fix is to move SeaBIOS to Kconfig.

Or if that is too big a step maybe config.h.in would be a useful
first step.


//Peter