Knuxify at 05:57, 27 January 2026

2026-01-27T05:57:51Z

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 This page serves as an introduction to the basics of mainlining.
 == Prerequisites ==
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 {{todo|pmOS wiki has links to talks and resources}}

Knuxify: Created page with "This page serves as an introduction to the basics of mainlining. == Prerequisites == * A computer running Linux, which will handle building the kernel. If you're on Windows, you can use WSL (though flashing the kernel to your device might be a bit challenging, TODO). (Note about recommended specs goes here; faster hardware is better, but only necessary bits are rebuilt on subsequent builds; also mention ccache?) * Some familiarity with the Linux shell and User:..."

2025-02-27T21:31:55Z

Created page with "This page serves as an introduction to the basics of mainlining. == Prerequisites == * A computer running Linux, which will handle building the kernel. ** If you're on Windows, you can use WSL (though flashing the kernel to your device might be a bit challenging, TODO). ** (Note about recommended specs goes here; faster hardware is better, but only necessary bits are rebuilt on subsequent builds; also mention ccache?) * Some familiarity with the Linux shell and User:..."

New page

This page serves as an introduction to the basics of mainlining.

== Prerequisites ==

* A computer running Linux, which will handle building the kernel.
** If you're on Windows, you can use WSL (though flashing the kernel to your device might be a bit challenging, TODO).
** (Note about recommended specs goes here; faster hardware is better, but only necessary bits are rebuilt on subsequent builds; also mention ccache?)
* Some familiarity with the Linux shell and [[User:Knuxify/Draft:C crash course|C programming language syntax]] is recommended.

== Getting to know your device and SoC ==

{{todo|These are both topics worthy of their own page. Some things to mention here:

* Finding out whether the SoC is supported to mainline and, if so, how well.
* Finding out what components your device has (it's nice to keep a table!)}}

== Preparing the build environment ==

In order to mainline a device, we need to be able to cross-compile the Linux kernel for it.

=== Downloading the Linux kernel source code ===

Depending on your SoC's support status:

* There may be an up-to-date maintained [[close-to mainline]] fork of the Linux kernel for your device's SoC; if there is one, start from it.
* If there is no dedicated fork for your device's SoC, or the fork is out of date, start with either:
** '''The latest stable tag''' directly from Torvalds' tree (see [https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/] or <code>github.com/torvalds/linux</code>).
** For very new SoCs with ongoing work, you may want to use the '''linux-next tree''' instead.

If you're on GitHub, you can fork [https://github.com/torvalds/linux the torvalds/linux repository] and start from there.

Once you have your kernel cloned, switch to the latest tag, then create a new feature branch from it:

<syntaxhighlight lang="shell-session">
$ git checkout v6.14 # replace 6.14 with latest kernel version
$ git checkout -b codename-mainline # git checkout -b creates a new branch based on current HEAD and checks out into it
</syntaxhighlight>

{{todo|Link to some nice guide on git here (and probably elsewhere in the page)}}

=== Cross-compiler setup ===

{{todo|Explain cross-compiler setup; where to get toolchains (AUR for Arch users? Linaro?), postmarketOS envkernel.sh}}

=== Selecting/creating a defconfig ===

The '''kernel config''' dictates which drivers and platform-specific support bits (including DTBs) get built. There are a handful of pre-made configs, called '''defconfigs''', in <code>arch/{arm,arm64,...}/configs</code> - use <code>make name_defconfig</code> to build them.

{{todo|Common ARM(64) config? Which options to select/unselect? pmbootstrap kconfig check might be useful here}}

=== Adding a device tree for your device ===

Devices using ARM chipsets use [[devicetree]]s to describe the hardware. See [[Devicetree/Writing a Linux device tree]] for a guide.

=== Building the kernel ===

{{todo|<code>make -j$(nproc)</code>}}

=== Packaging the kernel into a boot image ===

{{todo|See how I do it in [https://github.com/refractionware/linux/blob/meta/tools/mainline-tools mainline-tools], mention pmbootstrap build --envkernel?}}

Then, flash the resulting kernel to the device.

== Getting the kernel to boot ==

{{todo|UART, DTBO trickery}}

== See also ==

{{todo|pmOS wiki has links to talks and resources}}

User:Knuxify/Draft:Getting started - Revision history

Knuxify at 05:57, 27 January 2026