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android / kernel / common / refs/heads/android14-5.15
commit2cf61c95546e0f5a5a066192b082207d8aaf0db5[log] [tgz]
authorTodd Kjos <[email protected]>Mon Jan 27 20:53:47 2025 +0000
committerTodd Kjos <[email protected]>Tue Jan 28 12:33:51 2025 -0800
tree032b9ddb86e78792bf4fa5c3b9f0e31211bd7923
parent9b355fa5261b2d252bedc818a84a1da1619494c6 [diff]
ANDROID: KABI macros to release excess KABI fields for use with backports

With KMI freeze, we reserve padding in structs to be exclusively used
for LTS updates that would otherwise break the KMI. These fields are
reserved via the ANDROID_KABI_RESERVE() macro that adds a u64 field to
the struct. The ANDROID_KABI_USE() macro is used when the field is
needed for an LTS patch backport.

Since these fields must be reserved at KMI freeze time, we have make
our best guess at what might be needed - and sometimes reserve too many
fields. An example of this is the 8 ANDROID_KABI_RESERVE() fields in
`struct net_device` for android13-5.15. We are now 3 years into the
6 year lifetime for android13-5.15 and none of those 8 padding fields
have been used. At this point it is reasonable to allow 1 or 2 of those
fields to be used for non-LTS backports.

We won't relax the rule that ANDROID_KABI_RESERVE() is exclusively
for LTS backports, Instead we'll introduce a new macro,
ANDROID_KABI_BACKPORT_OK() to release some KABI fields for general use
as the branches age and the use of padding for LTS becomes unlikely.

We release the field for use by replacing the ANDROID_KABI_RESERVE()
with the new ANDROID_KABI_BACKPORT_OK() macro, which has the exact
same implementation, but allows others to use it for backporting
features from upstream.

When an ANDROID_KABI_BACKPORT_OK() field is going to be used, the
ANDROID_KABI_BACKPORT_USE() macro is used to indicate that the field
was used for a feature backport, not an LTS patch.

This patch adds the two new macros:

ANDROID_KABI_BACKPORT_OK() : exactly the same as ANDROID_KABI_RESERVE()
ANDROID_KABI_BACKPORT_USE() ; exacly the same as ANDROID_KABI_USE()

Patches that change an ANDROID_KABI_RESERVE() to ANDROID_KABI_BACKPORT_OK() must
be reviewed and get a CR+1 from gregkh@, joneslee@ or tkjos@ to make
sure it really is acceptable to reduce the padding for LTS merges.

Bug: 392673958
Signed-off-by: Todd Kjos <[email protected]>
Change-Id: I19b9dfc16d891fb6fe48ec4379c6fa3dcb6adf24
(cherry picked from commit f1954b6e6cba2533beb6dff539b9d0b079ceb665)
1 file changed
tree: 032b9ddb86e78792bf4fa5c3b9f0e31211bd7923
  1. android/
  2. arch/
  3. block/
  4. certs/
  5. crypto/
  6. Documentation/
  7. drivers/
  8. fs/
  9. include/
  10. init/
  11. io_uring/
  12. ipc/
  13. kernel/
  14. lib/
  15. LICENSES/
  16. mm/
  17. net/
  18. samples/
  19. scripts/
  20. security/
  21. sound/
  22. tools/
  23. usr/
  24. virt/
  25. .clang-format
  26. .cocciconfig
  27. .get_maintainer.ignore
  28. .gitattributes
  29. .gitignore
  30. .mailmap
  31. BUILD.bazel
  32. build.config.aarch64
  33. build.config.allmodconfig
  34. build.config.allmodconfig.aarch64
  35. build.config.allmodconfig.arm
  36. build.config.allmodconfig.x86_64
  37. build.config.amlogic
  38. build.config.arm
  39. build.config.common
  40. build.config.constants
  41. build.config.db845c
  42. build.config.gki
  43. build.config.gki-debug.aarch64
  44. build.config.gki-debug.x86_64
  45. build.config.gki.aarch64
  46. build.config.gki.aarch64.fips140
  47. build.config.gki.x86_64
  48. build.config.gki_kasan
  49. build.config.gki_kasan.aarch64
  50. build.config.gki_kasan.x86_64
  51. build.config.gki_kprobes
  52. build.config.gki_kprobes.aarch64
  53. build.config.gki_kprobes.x86_64
  54. build.config.khwasan
  55. build.config.rockpi4
  56. build.config.x86_64
  57. COPYING
  58. CREDITS
  59. Kbuild
  60. Kconfig
  61. Kconfig.ext
  62. MAINTAINERS
  63. Makefile
  64. modules.bzl
  65. OWNERS
  66. README
  67. README.md
README.md

How do I submit patches to Android Common Kernels

  1. BEST: Make all of your changes to upstream Linux. If appropriate, backport to the stable releases. These patches will be merged automatically in the corresponding common kernels. If the patch is already in upstream Linux, post a backport of the patch that conforms to the patch requirements below.

    • Do not send patches upstream that contain only symbol exports. To be considered for upstream Linux, additions of EXPORT_SYMBOL_GPL() require an in-tree modular driver that uses the symbol -- so include the new driver or changes to an existing driver in the same patchset as the export.
    • When sending patches upstream, the commit message must contain a clear case for why the patch is needed and beneficial to the community. Enabling out-of-tree drivers or functionality is not not a persuasive case.

  2. LESS GOOD: Develop your patches out-of-tree (from an upstream Linux point-of-view). Unless these are fixing an Android-specific bug, these are very unlikely to be accepted unless they have been coordinated with [email protected]. If you want to proceed, post a patch that conforms to the patch requirements below.

Common Kernel patch requirements

  • All patches must conform to the Linux kernel coding standards and pass scripts/checkpatch.pl
  • Patches shall not break gki_defconfig or allmodconfig builds for arm, arm64, x86, x86_64 architectures (see https://source.android.com/setup/build/building-kernels)
  • If the patch is not merged from an upstream branch, the subject must be tagged with the type of patch: UPSTREAM:, BACKPORT:, FROMGIT:, FROMLIST:, or ANDROID:.
  • All patches must have a Change-Id: tag (see https://gerrit-review.googlesource.com/Documentation/user-changeid.html)
  • If an Android bug has been assigned, there must be a Bug: tag.
  • All patches must have a Signed-off-by: tag by the author and the submitter

Additional requirements are listed below based on patch type

Requirements for backports from mainline Linux: UPSTREAM:, BACKPORT:

  • If the patch is a cherry-pick from Linux mainline with no changes at all
    • tag the patch subject with UPSTREAM:.
    • add upstream commit information with a (cherry picked from commit ...) line
    • Example:
      • if the upstream commit message is
        important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <[email protected]>
  • then Joe Smith would upload the patch for the common kernel as
        UPSTREAM: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <[email protected]>

        Bug: 135791357
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        (cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
        Signed-off-by: Joe Smith <[email protected]>
  • If the patch requires any changes from the upstream version, tag the patch with BACKPORT: instead of UPSTREAM:.
    • use the same tags as UPSTREAM:
    • add comments about the changes under the (cherry picked from commit ...) line
    • Example:
        BACKPORT: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <[email protected]>

        Bug: 135791357
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        (cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
        [joe: Resolved minor conflict in drivers/foo/bar.c ]
        Signed-off-by: Joe Smith <[email protected]>

Requirements for other backports: FROMGIT:, FROMLIST:,

  • If the patch has been merged into an upstream maintainer tree, but has not yet been merged into Linux mainline
    • tag the patch subject with FROMGIT:
    • add info on where the patch came from as (cherry picked from commit <sha1> <repo> <branch>). This must be a stable maintainer branch (not rebased, so don't use linux-next for example).
    • if changes were required, use BACKPORT: FROMGIT:
    • Example:
      • if the commit message in the maintainer tree is
        important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <[email protected]>
  • then Joe Smith would upload the patch for the common kernel as
        FROMGIT: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <[email protected]>

        Bug: 135791357
        (cherry picked from commit 878a2fd9de10b03d11d2f622250285c7e63deace
         https://git.kernel.org/pub/scm/linux/kernel/git/foo/bar.git test-branch)
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <[email protected]>
  • If the patch has been submitted to LKML, but not accepted into any maintainer tree
    • tag the patch subject with FROMLIST:
    • add a Link: tag with a link to the submittal on lore.kernel.org
    • add a Bug: tag with the Android bug (required for patches not accepted into a maintainer tree)
    • if changes were required, use BACKPORT: FROMLIST:
    • Example:
        FROMLIST: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <[email protected]>

        Bug: 135791357
        Link: https://lore.kernel.org/lkml/[email protected]/
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <[email protected]>

Requirements for Android-specific patches: ANDROID:

  • If the patch is fixing a bug to Android-specific code
    • tag the patch subject with ANDROID:
    • add a Fixes: tag that cites the patch with the bug
    • Example:
        ANDROID: fix android-specific bug in foobar.c

        This is the detailed description of the important fix

        Fixes: 1234abcd2468 ("foobar: add cool feature")
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <[email protected]>
  • If the patch is a new feature
    • tag the patch subject with ANDROID:
    • add a Bug: tag with the Android bug (required for android-specific features)