[PATCH v10 0/7] rust: DebugFS Bindings

[Matthew Maurer <mmaurer@google.com>]

This series provides safe DebugFS bindings for Rust, with sample
modules using them.

Shortly after this is sent, you will see a real driver WIP using this
implenting the qcom socinfo driver.

Signed-off-by: Matthew Maurer <mmaurer@google.com>
---
Changes in v10:
- Introduced Scoped to show how either a File or Dir can be bound to
  data
- Remove use of `use<>` for MSRV compatibility
- Added Write support
- Added more complex sample driver using scoped interface
- Updated original sample driver to use writes to drive mutation
- Added `FileOps<T>` (only for DebugFS, not a kernel-wide abstraction)
  to decrease needed `unsafe` for keeping vtables paired to types.
- Centralized `dentry` lifecycle management to `entry.rs`.
- Link to v9: https://lore.kernel.org/r/20250709-debugfs-rust-v9-0-92b9eab5a951@google.com

Changes in v9:
- Switched to `PinInit` backing instead of `ForeignOwnable`
- Changed sample to be a platform driver
- Exported a static property
- Demonstrated runtime mutation in platform driver (`inc_counter`)
- Demonstrated how driver code would interact with data structures
  exported through DebugFS (`Wrapper`)
- Link to v8: https://lore.kernel.org/r/20250627-debugfs-rust-v8-0-c6526e413d40@google.com

Changes in v8:
- Switched from casts to `core::from_{ref, mut}` in type change
- Link to v7: https://lore.kernel.org/r/20250624-debugfs-rust-v7-0-9c8835a7a20f@google.com

Changes in v7:
- Rewrote `entry::Entry` -> `Entry`
- Use `c_int` and `c_void` from kernel prelude rather than core
- Removed unnecessary `display_open` cast
- Switched from `Deref` + an explicit box to `ForeignOwnable` for
  attaching owned data.
- Made `&'static` and `&'static mut` implement `ForeignOwnable`
- Swapped "driver" to "module" in sample code
- Link to v6: https://lore.kernel.org/r/20250618-debugfs-rust-v6-0-72cae211b133@google.com

Changes in v6:
- Replaced explicit lifetimes with children keeping their parents alive.
- Added support for attaching owned data.
- Removed recomendation to only keep root handles and handles you want
  to delete around.
- Refactored some code into separate files to improve clarity.
- Link to v5: https://lore.kernel.org/r/20250505-debugfs-rust-v5-0-3e93ce7bb76e@google.com

Changes in v5:
- Made Dir + File wrappers around Entry
- All functions return owning handles. To discard without drop, use
  `forget`. To keep a handle without drop, use `ManuallyDrop`.
- Fixed bugs around `not(CONFIG_DEBUG_FS)`
- Removed unnecessary `addr_of!`
- Link to v4: https://lore.kernel.org/r/20250502-debugfs-rust-v4-0-788a9c6c2e77@google.com

Changes in v4:
- Remove SubDir, replace with type-level constant.
- Add lifetime to Dir to prevent subdirectories and files from outliving
  their parents and triggering an Oops when accessed.
- Split unsafe blocks with two calls into two blocks
- Access `private` field through direct pointer dereference, avoiding
  creation of a reference to it.
- Notably not changed - owning/non-owning handle defaults. The best read
  I had from the thread was to continue with this mode, but I'm willing
  to change if need be.
- Comment changes
  - More comment markdown
  - Remove scopes from examples
  - Put `as_ptr` properties into a `# Guarantees` section.
- Link to v3: https://lore.kernel.org/r/20250501-debugfs-rust-v3-0-850869fab672@google.com

Changes in v3:
- Split `Dir` into `Dir`/`SubDir`/`File` to improve API.
- Add "." to end of all comments.
- Convert INVARIANT to # Invariants on types.
- Add backticks everywhere I found variables/types in my comments.
- Promoted invariant comment to doc comment.
- Extended sample commenting to make it clearer what is happening.
- Link to v2: https://lore.kernel.org/r/20250430-debugfs-rust-v2-0-2e8d3985812b@google.com

Changes in v2:
- Drop support for builder / pinned bindings in initial series
- Remove `ARef` usage to abstract the dentry nature of handles
- Remove error handling to discourage users from caring whether DebugFS
  is enabled.
- Support CONFIG_DEBUG_FS=n while leaving the API available
- Fixed mistaken decimal/octal mixup
- Doc/comment cleanup
- Link to v1: https://lore.kernel.org/r/20250429-debugfs-rust-v1-0-6b6e7cb7929f@google.com

---
Matthew Maurer (7):
      rust: debugfs: Add initial support for directories
      rust: debugfs: Add support for read-only files
      rust: debugfs: Add support for writable files
      rust: debugfs: Add support for callback-based files
      samples: rust: Add debugfs sample driver
      rust: debugfs: Add support for scoped directories
      samples: rust: Add scoped debugfs sample driver

 MAINTAINERS                              |   4 +
 rust/bindings/bindings_helper.h          |   1 +
 rust/kernel/debugfs.rs                   | 613 +++++++++++++++++++++++++++++++
 rust/kernel/debugfs/callback_adapters.rs | 122 ++++++
 rust/kernel/debugfs/entry.rs             | 164 +++++++++
 rust/kernel/debugfs/file_ops.rs          | 246 +++++++++++++
 rust/kernel/debugfs/traits.rs            |  97 +++++
 rust/kernel/lib.rs                       |   1 +
 samples/rust/Kconfig                     |  22 ++
 samples/rust/Makefile                    |   2 +
 samples/rust/rust_debugfs.rs             | 151 ++++++++
 samples/rust/rust_scoped_debugfs.rs      | 134 +++++++
 12 files changed, 1557 insertions(+)
---
base-commit: f3c5631f70e434e318c44001e2417d4770f06cd0
change-id: 20250428-debugfs-rust-3cd5c97eb7d1

Best regards,
-- 
Matthew Maurer <mmaurer@google.com>