Using a 5.2 Kernel

[Keith I Myers]

Good Morning All,

Do you think there would be any issues with using a 5.X kernel on a build of ChromiumOS? I have built many kernels for Ubuntu/Debian without much of an issue but wanted to be sure.

Would I just do a git clone of the upstream kernel and copy the contents of the chromos/scripts from a existing kernel?

--

Keith I Myers http://KMyers.me Mobile : (305)-929-3475

[Sean Paul]

On Fri, Jul 19, 2019 at 1:29 PM Keith I Myers
<keithiok...@gmail.com> wrote:
>
> Good Morning All,
> Do you think there would be any issues with using a 5.X kernel on a build of ChromiumOS? I have built many kernels for Ubuntu/Debian without much of an issue but wanted to be sure.
>

The only issues you'll face will be related to how well supported your
chromebook is upstream.

> Would I just do a git clone of the upstream kernel and copy the contents of the chromos/scripts from a existing kernel?
>

It's probably easier than that. Just add the upstream repo as a remote
to the appropriate third_party/kernel/vX.X chrome repo and check out
the appropriate branch. The build system will use the defconfig from
third_party/chromiumos-overlay/eclass/cros-kernel/<platform>_defconfig,
so you can emerge-<BOARD> as normal.

To give you an idea about what's involved, instructions for kevin are
here [1]. Most of the hard work in this doc is pulling in downstream
patches to make up for lacking upstream support. If you're using an
intel device it's probably just a matter of git remote/checkout,
build, deploy.

[1] https://www.chromium.org/chromium-os/how-tos-and-troubleshooting/mainline-kernel-on-kevin-chromebook-plus/chrome-os-mainline-kernel-on-kevin-chromebook-plus


Sean

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> Mobile : (305)-929-3475
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[Adam Kearn]

Did you get it working in the end Keith?

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[Chintan Patel]

I was under impression that after checking out upstream branch, we also need to place/checkout chromeos directory in order to pick chromeos kernel configs. Is my understanding is correct or we don't need to do this?  

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[Brian Norris]

There are fallback configs provided here:

https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/refs/heads/master/eclass/cros-kernel/

Those are maintained on a best effort basis (some of them are
extremely unloved), and we generally try to keep them mostly working
on at least the last few upstream releases (e.g., if a CONFIG_* symbol
gets renamed, we might leave both in the config). But
rockchip64_defconfig, for instance, should generally work for RK3399,
as I and a few others regularly test that one.

[Chintan Patel]

Good to know... thanks Brian!

[Brian Norris]

You're welcome! I hope it also goes without saying: patches (or, CLs)
welcome. We'd all love to see more people testing out upstream Linux
on their Chrom{e,ium} OS.

[Keith I Myers]

Good Morning Brian,

Is there a specific $USE flag that needs to be passed to tell the build system to use the upstream kernel?

[Brian Norris]

No. See Sean Paul's original reply to you as well, where he just suggests you check out the appropriate upstream git remote from within your applicable .../kernel/vX.Y directory (and run cros_workon-${BOARD} start chromeos-kernel-X_Y). The the normal emerge / build_packages will build that source tree instead of the original chromeos-X.Y kernel source tree. No USE flags involved.

The instructions he pointed at [1] cover some version of that as well as some graphics-related stuff specific to RK3399 that you may not need.

[1] https://www.chromium.org/chromium-os/how-tos-and-troubleshooting/mainline-kernel-on-kevin-chromebook-plus/chrome-os-mainline-kernel-on-kevin-chromebook-plus

[Keith I Myers]

I must be missing something, does this look right?

export BOARD=amd64-generic
mkdir -p ~/trunk/src/third_party/kernel/v5.3/
cd ~/trunk/src/third_party/kernel/v5.3/
git init
pushd ~/trunk/src/third_party/kernel/v5.3/ && \
    git remote add torvalds git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git && \
    git fetch torvalds && \
    popd

I then try to run cros_workon-${BOARD} start chromeos-kernel-5.3 and it fails with

(cr) kmyers@office ~/trunk/src/third_party/kernel $ cros_workon-${BOARD} start chromeos-kernel-5.3                                                           12:36:16: WARNING: Could not find canonical package for "chromeos-kernel-5.3"
12:36:16: ERROR: Error parsing package list

[Brian Norris]

The recommendations were all to reuse the existing directories and ebuilds. So for amd64-generic, that would be the 4.14 kernel directory.

Adding a whole new ebuild is a bit more work, and isn't really necessary when just doing local builds.

[Keith I Myers]

Ok, thanks for the clarification.