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android/kernel/common/0fd55a309793adc6b8cddb5c29e80caa545ba4bb
commit
0fd55a309793adc6b8cddb5c29e80caa545ba4bb
[log]
author
Isaac J. Manjarres <isaacmanjarres@google.com>
Thu Apr 30 23:40:26 2026 +0000
committer
android-test-infra-autosubmit@system.gserviceaccount.com <android-test-infra-autosubmit@system.gserviceaccount.com>
Fri Jul 17 11:37:23 2026 -0700
tree
ab6f14bf61eab34cd66cd53a64fb410f5a3fc909
parent
cbc99054b5a962b6086f4b71d2d36d917a3991a1 [diff]
ANDROID: drivers/wrapfd: Support unaligned file/buffer offsets

The existing file loading logic requires that the caller's file and
buffer offsets be page aligned. The reasons for this requirements is
that the dmabuf file loading support instructs the VFS and block layer
to directly load the file contents into the dmabuf, which requires
strict alignment around the file offset, read length, and buffer
addresses--specifically that all three be page aligned.

These requirements can be restrictive and are just an implementation
detail of how the wrapfd driver loads file content into wrapped buffers.

Therefore, add support for unaligned file/buffer offsets for dmabufs
and relax the requirements around those offsets. This can be achieved
by breaking up the file load into a maximum of three parts:

- A bounce page for the content in the first page of the file, if either
  the buffer or file offsets aren't aligned. Otherwise, we risk
  overwriting data in the first page of the user-provided buffer.

- Loading as much data as possible directly into the buffer without
  going past the allowed range.

- At most two bounce pages for the content not captured by the two
  buffers described above.

Once the loading is complete, the data can be copied from the bounce
pages to their final destination, and if required, the data can also
be shifted from where it is offset in the buffer.

Naturally, this comes at a penalty when compared to the case where
the length of the read, and the file and buffer offsets are all
page-aligned.

Add testcases with unaligned file/buffer offsets as well.

Bug: 480234490
Change-Id: Id41970823e104bbb756183d29ae0c2532577ff67
Signed-off-by: Isaac J. Manjarres <isaacmanjarres@google.com>
2 files changed
tree: ab6f14bf61eab34cd66cd53a64fb410f5a3fc909
  1. arch/
  2. bazel/
  3. block/
  4. certs/
  5. crypto/
  6. Documentation/
  7. drivers/
  8. fs/
  9. gki/
  10. include/
  11. init/
  12. io_uring/
  13. ipc/
  14. kernel/
  15. lib/
  16. LICENSES/
  17. mm/
  18. net/
  19. rust/
  20. samples/
  21. scripts/
  22. security/
  23. sound/
  24. tools/
  25. usr/
  26. virt/
  27. .clang-format
  28. .clippy.toml
  29. .cocciconfig
  30. .editorconfig
  31. .get_maintainer.ignore
  32. .gitattributes
  33. .gitignore
  34. .mailmap
  35. .rustfmt.toml
  36. abi.bzl
  37. BUILD.bazel
  38. build.config.aarch64
  39. build.config.arm
  40. build.config.common
  41. build.config.constants
  42. build.config.db845c
  43. build.config.gki
  44. build.config.gki.aarch64
  45. build.config.gki.x86_64
  46. build.config.rockpi4
  47. build.config.x86_64
  48. COPYING
  49. CREDITS
  50. Kbuild
  51. Kconfig
  52. Kconfig.ext
  53. MAINTAINERS
  54. Makefile
  55. modules.bzl
  56. OWNERS
  57. OWNERS_DrNo
  58. README
  59. 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 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 kernel-team@android.com. 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 <fred.jones@foo.org>
  • 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 <fred.jones@foo.org>

        Bug: 135791357
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        (cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • 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 <fred.jones@foo.org>

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

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 <fred.jones@foo.org>
  • 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 <fred.jones@foo.org>

        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 <joe.smith@foo.org>
  • 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 <fred.jones@foo.org>

        Bug: 135791357
        Link: https://lore.kernel.org/lkml/20190619171517.GA17557@someone.com/
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If a patch has been submitted to the community, but rejected, do NOT use the FROMLIST: tag to try to hide this fact. Use the ANDROID: tag as described below as this must be considered as an Android-specific submission, not an upstream submission as the community will not accept these changes as-is.

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 <joe.smith@foo.org>
  • 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)