Occasionally, I will forget to link something from the mailing list in this post. To see my full mailing list activity (patches, reviews, and reports), you can view it on lore.kernel.org.

Linux kernel patches

  • Android changes: Android is one of the largest downstream consumers of our work. Our continuous integeration tests the Android trees with newer versions of LLVM to help catch any issues that will impact Android once they upgrade their version of LLVM, which can lag behind at times.

  • Build errors: These are patches to fix various build errors that I found through testing different configurations with LLVM or were exposed by our continuous integration setup. The kernel needs to build in order to be run :)

    • ntb_perf: Fix 64-bit division on 32-bit architectures (v1)
    • arm64: vdso32: Small fixes for ld.lld 11 and CONFIG_DEBUG_INFO (v1)

  • Miscellaneous fixes: These are fixes that don’t fit into a particular category but are important to ClangBuiltLinux. In this case, I noticed that Chimera Linux was carrying a patch downstream to enable the stackprotector on x86_64 when cross compiling, which typically means the --target flag is missing somewhere, which I fixed with this patch.

    • x86/Kconfig: Fix CONFIG_CC_HAS_SANE_STACKPROTECTOR when cross compiling with clang (v1)

  • Stable patches and backport requests: It is important to make sure that the stable trees are as free from issues as possible, as those are the trees that devices and users use; for example, Android and Chrome OS regularly merge from stable, so if there is a problem that will impact those trees that we fixed in mainline, it should be backported.

  • Warning fixes: These are patches to fix various warnings that appear with LLVM. I used to go into detail about the different warnings and what they mean, but the important takeaway for this section is that the kernel should build warning free, as all developers should be using CONFIG_WERROR, which will turn these all into failures. Maybe these should be in the build failures section…

    • mmc: sdhci-brcmstb: Initialize base_clk to NULL in sdhci_brcmstb_probe() (v1)
    • soc: mediatek: SVS: Use DEFINE_SIMPLE_DEV_PM_OPS for svs_pm_ops (v1)
    • drm/amd/display: Fix indentation in dcn32_get_vco_frequency_from_reg() (v1)

Patch review and input

For the next sections, I link directly to my first response in the thread when possible but there are times where the link is to the main post. My responses can be seen inline by going to the bottom of the thread and clicking on my name.

Reviewing patches that are submitted is incredibly important, as it helps ensure good code quality due to catching mistakes before the patches get accepted and it can help get patches accepted faster, as some maintainers will blindly pick up patches that have been reviewed by someone that they trust.

Issue triage and reporting

The unfortunate thing about working at the intersection of two projects is we will often find bugs that are not strictly related to the project, which require some triage and reporting back to the original author of the breakage so that they can be fixed and not impact our own testing. Some of these bugs fall into that category while others are issues strictly related to this project.

Tooling improvements

These are changes to various tools that we use, such as our continuous integration setup, booting utilities, toolchain building scripts, or other closely related projects such as AOSP’s distribution of LLVM and TuxMake.

Behind the scenes

  • Every day that there is a new linux-next release, I rebase and build a few different kernel trees then boot and runtime test them on several different machines, including a Windows Subsystem for Linux instance, a Raspberry Pi 3 and 4, an Intel-based desktop, an AMD-based desktop, and an Intel-based laptop. This is not always visible because I do not report anything unless there is something broken but it can take up to a few hours each day, depending on the amount of churn and issues uncovered.

Special thanks to: