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Upstream First

Abstract

This document outlines a process for managing the flow of kernel source patches between Chromium OS and hardware partners. 

Goals

Our goal with the "Upstream First" policy is to eliminate kernel version fragmentation.

We know that hardware partners support other devices as well as Chromium OS-based devices. So rather than having partners target multiple kernels for multiple devices, we'd like to encourage them to target one kernel: the upstream kernel. 

By having everyone target a single kernel, we hope to avoid duplication of effort and get everyone (our hardware partners, their partners, and the upstream community) working together on improving a single set of patches. By working together, we can build a better kernel and avoid later having to rework changes that are incompatible with the upstream kernel.

Accepting patches

A device driver patch must be accepted upstream before it can be accepted into the Chromium OS kernel. Ideally, the patch will be in Linus Torvalds's kernel tree before it is accepted into the Chromium OS kernel. However, other options are also available.

The following list shows options for getting a patch accepted into the Chromium OS kernel. We encourage all partners to strive to attain option 1.

Patch options, ordered from high to low preference
  1. The patch is accepted into Linus Torvalds's upstream tree.
  2. The patch is accepted into the subsystem maintainer tree (such as Dave Miller's netdev tree).
  3. The patch is accepted into the the device maintainer tree (such as samsung or msm) and a pull request has been sent to Linus Torvalds.
After the patch is accepted into an upstream tree, Google will cherry-pick it into the Chromium OS kernel. If the patch requires backport work, Google will work with the vendor to do the backport.

Exemptions are granted on a case-by-case basis.
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