adoc

maintainers.adoc

@@ -0,0 +1,90 @@
+[[maintainers]]
+= Maintainers
+
+[[how-to-update-the-linux-kernel]]
+== How to update the Linux kernel?
+
+....
+# Last point before out patches.
+last_mainline_revision=v4.14
+next_mainline_revision=v4.15
+cd linux
+
+# Create a branch before the rebase.
+git branch "lkmc-${last_mainline_revision}"
+git remote set-url origin git@github.com:cirosantilli/linux.git
+git push
+
+git remote add up git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
+git fetch up
+git rebase --onto "$next_mainline_revision" "$last_mainline_revision"
+./build -t linux-reconfigure
+# Manually fix our kernel modules if necessary.
+
+cd ..
+git branch "buildroot-2017.08-linux-${last_mainline_revision}"
+git add .
+git commit -m "Linux ${next_mainline_revision}"
+git push
+....
+
+and update the README!
+
+During update all you kernel modules may break since the kernel API is
+not stable.
+
+They are usually trivial breaks of things moving around headers or to
+sub-structs.
+
+The userland, however, should simply not break, as Linus enforces strict
+backwards compatibility of userland interfaces.
+
+This backwards compatibility is just awesome, it makes getting and
+running the latest master painless.
+
+This also makes this repo the perfect setup to develop the Linux kernel.
+
+[[how-to-downgrade-the-linux-kernel]]
+== How to downgrade the Linux kernel?
+
+The kernel is not forward compatible, however, so downgrading the Linux
+kernel requires downgrading the userland too to the latest Buildroot
+branch that supports it.
+
+The default Linux kernel version is bumped in Buildroot with commit
+messages of type:
+
+....
+linux: bump default to version 4.9.6
+....
+
+So you can try:
+
+....
+git log --grep 'linux: bump default to version'
+....
+
+Those commits change `BR2_LINUX_KERNEL_LATEST_VERSION` in
+`/linux/Config.in`.
+
+You should then look up if there is a branch that supports that kernel.
+Staying on branches is a good idea as they will get backports, in
+particular ones that fix the build as newer host versions come out.
+
+[[how-to-add-new-buildroot-options]]
+== How to add new Buildroot options?
+
+....
+cd buildroot/output.x86_64~
+make menuconfig
+....
+
+Hit `/` and search for the settings.
+
+Save and quit.
+
+....
+diff .config.olg .config
+....
+
+Copy and paste the diff additions to `buildroot_config_fragment`.