linux-kernel - [PATCH v4 0/3] rust: miscdevice: add additional data to MiscDeviceRegistration

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Message-Id: <20250530-b4-rust_miscdevice_registrationdata-v4-0-d313aafd7e59@gmail.com>
Date: Fri, 30 May 2025 22:46:26 +0200
From: Christian Schrefl <chrisi.schrefl@...il.com>
To: Miguel Ojeda <ojeda@...nel.org>, Danilo Krummrich <dakr@...nel.org>, 
 Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>, 
 Gary Guo <gary@...yguo.net>, 
 Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
 Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
 Trevor Gross <tmgross@...ch.edu>, Arnd Bergmann <arnd@...db.de>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Lee Jones <lee@...nel.org>, 
 Daniel Almeida <daniel.almeida@...labora.com>, 
 Benno Lossin <lossin@...nel.org>, Benno Lossin <lossin@...nel.org>
Cc: Gerald Wisböck <gerald.wisboeck@...ther.ink>, 
 rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Christian Schrefl <chrisi.schrefl@...il.com>
Subject: [PATCH v4 0/3] rust: miscdevice: add additional data to
 MiscDeviceRegistration

Currently there is no good way to pass arbitrary data from the driver to
a `miscdevice` or to share data between individual handles to a 
`miscdevice` in rust.

This series adds additional (generic) data to the MiscDeviceRegistration
for this purpose.

The first patch originally comes from my `UnsafePinned` patch series [0].

The second patch implements the changes and fixes the build of the sample
without changing any functionality (this is currently the only in tree 
user).

The third patch changes the `rust_misc_device` sample to use this to 
share the same data between multiple handles to the `miscdevice`.
I have tested the sample with qemu and the C userspace example
from the doc comments.

Some discussion on Zulip about the motivation and approach [1].
Thanks a lot to everyone helping me out with this.

This patch series is based on the rust-next branch.

Link: https://lore.kernel.org/rust-for-linux/20250511-rust_unsafe_pinned-v4-2-a86c32e47e3d@gmail.com/  [0]
Link: https://rust-for-linux.zulipchat.com/#narrow/channel/288089-General/topic/Passing.20a.20DevRes.20to.20a.20miscdev/near/494553814 [1]

Signed-off-by: Christian Schrefl <chrisi.schrefl@...il.com>
---
Changes in v4:
- Rework to use Opaque instead of `UnsafePinned`.
- Include `impl Wrapper for Opaque` patch.
- Link to v3: https://lore.kernel.org/r/20250517-b4-rust_miscdevice_registrationdata-v3-0-cdb33e228d37@gmail.com

Changes in v3:
- Rebased on top of my `UnsafePinned` series.
- Link to v2: https://lore.kernel.org/r/20250131-b4-rust_miscdevice_registrationdata-v2-0-588f1e6cfabe@gmail.com

Changes in v2:
- Don't use associated_type_bounds since the MSRV does not support
    that on stable yet (Kernel test robot)
- Doc changes and add intra-doc links (Miguel)
- Use container_of macro instead of pointer cast in `fops_open` (Greg)
- Rename `Aliased` to `UnsafePinned` (Boqun)
- Make sure Data is initialized before `misc_register` is called
- Rework the example to use an additional shared value instead of 
    replacing the unique one
- Expanded the c code for the example to use the new ioctls
- Link to v1: https://lore.kernel.org/r/20250119-b4-rust_miscdevice_registrationdata-v1-0-edbf18dde5fc@gmail.com

---
Christian Schrefl (3):
      rust: implement `Wrapper<T>` for `Opaque<T>`
      rust: miscdevice: add additional data to MiscDeviceRegistration
      rust: miscdevice: adjust the rust_misc_device sample to use RegistrationData.

 rust/kernel/miscdevice.rs        |  79 +++++++++++++++++++-------
 rust/kernel/revocable.rs         |   2 +
 rust/kernel/types.rs             |  25 ++++----
 samples/rust/rust_misc_device.rs | 120 ++++++++++++++++++++++++++++++++++++---
 4 files changed, 185 insertions(+), 41 deletions(-)
---
base-commit: a3b2347343e077e81d3c169f32c9b2cb1364f4cc
change-id: 20250119-b4-rust_miscdevice_registrationdata-a11d88dcb284

Best regards,
-- 
Christian Schrefl <chrisi.schrefl@...il.com>