This is to follow up from the discussion yesterday during the UEFI
hacking sprint at the Linaro offices.
I've been playing around with git and repo to figure out how best to
manage Linaro's UEFI tree. First, a summary of the methods I've looked
at:
1) git sub-modules
2) git sub-trees
3) repo
1) git sub-modules
A submodule is and external reference from one git repo to another so
that the submodule appears as a sub directory in the working
directory. The link is by reference using the SHA1 id from the
submodule's git tree and none of the submodules files are tracked in
the master tree.
Git keeps track of both the submodule's git url and SHA1 id as files
in revision control so that the specific version of the submodule gets
tracked. Changes to the submodule upstream are pulled in by committing
a change to the SHA1 id (the tool takes care of doing this
correctly)..
Changes to a submodule must be pushed out to the submodule git URL
before the master tree will be able to see them. Care must be taken to
not push out submodule references that aren't already in the
submodule's master repository.
Work flow requires end users to do extra steps to fetch submodules
after cloning a tree:
References appear to be only by SHA1 id, not by tag or branch. It's
difficult to see at a glance what branch a sub module comes from.
However, going into the subtree and doing a "git pull" does appear to
work for tracking the submodule's git repo.
Sub module must be entirely contained in a single subdirectory path.
No complex fan out across the repo allowed
2) git subtrees
Git subtrees pull a copy of another git tree directly into the git
repository. May optionally include the history of the subtree.
Files become part of the master repo and so one repo contains
everything needed by users. If history is include, then all of the
subtrees commits become part of the git history of the whole tree.
Same as with submodules, a subtree is attached to a specific point in
git-history time. The commit text could state which branch was merged
from the subtree repo, but just looking at a subtree merge commit
doesn't say what branch it came from, or which branch should be
tracked for updates
Subtree can either be constrained to a single subdirectory, or make
changes across the tree. If the subtree directory layout exactly
matches the master repo (at the same directory level, not in a
subdirectory) then the git history becomes transparent. When in a
subdirectory, git log won't follow the file history across the subtree
merge point.
For end users git subtrees are transparent. Clone the tree and go.
3) Repo
External tool on top of git
Fetches and extracts multiple git repos into a single complex of
working directories
https://gerrit.googlesource.com/git-repo
- Integrated with 'Gerrit" review tool, but does not require using gerrit
- Each repo gets a seperate directory. It doesn't look like one can be
a subdirectory of another, but it should be possible to create
symlinks between them
- The repo can be configured to follow a branch on each tree, or be
locked to a specific tag. All is stored in a git repo so is kept under
revision control.
- Figuring out how to write a repo default.xml manifest file wasn't
obvious, but it is a one-time setup thing. Once working it won't need
to be manipulated frequently.
- A canned repo file could make it easy to pull in the various sub
projects needed to build a working UEFI image.
- Possible downside; repo *really* likes to update itself from the
upstream repo .git tree. That is potentially a risk if the upstream
repo moves or otherwise stops working. No data would be lost, but it
could be a denial-of-service kind of error.
Okay, that ended up being a long email. I've got some examples below,
but I'll save a discussion of how best to maintain the linaro uefi
rollup tree to a separate email.
g.
Sub-module Examples:
Creating a submodule:
$ git submodule add git://path/to/submodule/git SecretSubModule
$ git status
# On branch master
# Your branch is ahead of 'origin/master' by 39 commits.
#
# Changes to be committed:
# (use "git reset HEAD <file>..." to unstage)
#
# new file: .gitmodules
# new file: SecretSubmodulePkg
#
$ git diff --staged
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..95e9d58
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "SecretSubmodulePkg"]
+ path = SecretSubmodulePkg
+ url = git:///path/to/submodule/git
diff --git a/SecretSubmodulePkg b/SecretSubmodulePkg
new file mode 160000
index 0000000..b4e3b57
--- /dev/null
+++ b/SecretSubmodulePkg
@@ -0,0 +1 @@
+Subproject commit b4e3b579a47bc67011738fa938bbbc3758826f4c
$ git comiit
Updating submodule:
$ cd SecretSubmodulePkg/
$ git pull
remote: Counting objects: 5, done.
remote: Compressing objects: 100% (3/3), done.
remote: Total 3 (delta 0), reused 0 (delta 0)
Unpacking objects: 100% (3/3), done.
>From file:///home/grant/hacking/uefi-working/SecretPkg
b4e3b57..a9859ea master -> origin/master
Updating b4e3b57..a9859ea
Fast-forward
README | 2 ++
1 file changed, 2 insertions(+)
$ cd ..
$ git diff
diff --git a/SecretSubmodulePkg b/SecretSubmodulePkg
index b4e3b57..a9859ea 160000
--- a/SecretSubmodulePkg
+++ b/SecretSubmodulePkg
@@ -1 +1 @@
-Subproject commit b4e3b579a47bc67011738fa938bbbc3758826f4c
+Subproject commit a9859ea6ebbf196a5398676d342c3257fb00dd3f
$ git commit -a
[master bb730a6] Pull in latest SecretSubmodulePkg submodule
1 file changed, 1 insertion(+), 1 deletion(-)
Retrieving a git tree with submodules (both master and submodule trees
need to be accessable to user):
$ git clone git://path/to/master/git master
$ cd master
$ git submodule init
$ git submodule update
Repo example:
First create a new git repo to contain the manifest file:
$ mkdir uefi-manifest
$ cd uefi-manifest
$ git init-db
$ cat > default.xml << EOF
<?xml version="1.0" encoding="UTF-8"?>
<manifest>
<remote name="origin" fetch="git://path/to/git/repos/"/>
<default remote="origin" revision="master"/>
<project name="edk2-sourceforge" path="EDK2"/>
<project name="Origen-EDK-II-Package" path="Origen"/>
<project name="SecretPkg" path="SecretPkg"/>
</manifest>
EOF
$ git add default.xml
$ git commit
$ cd ..
Download repo
$ curl https://dl-ssl.google.com/dl/googlesource/git-repo/repo > ~/bin/repo
$ chmod a+x ~/bin/repo
Then initialize the repo:
$ mkdir working-tree
$ cd working-tree
$ repo init -u git://path/to/manifest/git/repo.git
$ repo sync
Now all the git trees will be fetched and copied into the working directory.
--
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
Hi,
This must be set when cpu comes out of reset, and only cleared if the
cpu is being powered down.
at other times SMP bit must be enabled, even if the cpu is AMP system.
Boot code take care of this , but Kernel don't care this config.
steve.zhan
2012/12/19 <boot-architecture-request(a)lists.linaro.org>
> if the SMP bit of ACTLR ACTLR[6] is not set to one. This
> seems to be different for A15
>
--
Steve Zhan
Hi,
I have tried to use the Linux kernels for ARM to generate kernel image for
CortexA7 and CortexA15 and had a question about the initialization boot
code. One difference between A7 and A15 seems to be that the ARM Cortex A7
TRM mentions that in both uni and multi-processor environment, the caches
will be unusable if the SMP bit of ACTLR ACTLR[6] is not set to one. This
seems to be different for A15. I looked at the processor specific
initialization code in the Linaro kernel but couldn't find the bit being
set. Is there any specific build that you can point me to that does this?.
If this is not done, it almost appears like A7 can never use its caches
(atleast TRM seems to be very explicit about it). Please kindly advice. Any
documentation/input in this regard would be very helpful.
Thanks!
I'm looking at the various trees that are relevant for doing UEFI
development. It's not clear which trees I should be working from,
particularly for the git mirrors. Here's what I've found so far.
Upstream Tianocore:
- Upstream is an SVN tree on sourceforge
- I've found several git mirrors of the SVN trees
- many on github
- Looks like sourceforge also maintains mirrors:
http://tianocore.git.sourceforge.net/git/gitweb-index.cgi
To keep the trees compatible, we need to all be working from the same
SVN mirror source. I assume the mirror on Sourceforge is the one to
use, am I correct?
Linaro Tianocore:
- git://git.linaro.org/arm/uefi/uefi.git
- Directory layout does *not* match the sourceforge git mirror. What
mirror is this tree based on?
BaseTools:
- From our discussion yesterday at the Linaro office, my understanding
is that BaseTools is actively developed, but only rarely syncronized
with EDKII tree (about 6mth period).
- https://edk2-buildtools.svn.sourceforge.net/svnroot/edk2-buildtools/trunk/B…
- Linaro *may* want to pull in tip of basetools instead of the version
in upstream when creating a Linaro UEFI branch
Platform Support
- Yesterday we discussed the idea of keeping platform support in a
separate git repo for each platform. ie, something like
SamsungPlatformPkg
- git clone git://github.com/girishks/Origen-EDK-II-Package.git
- The Linaro tree would have to pull in each of the supported
platforms; either by merging in each git tree, or using something like
'repo' to create a working directory from multiple git trees.
Are there any other trees that I need to pay attention to?
g.
--
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
