linux-kernel - [PATCH v2 0/3] rust: miscdevice: Add additional data to MiscDeviceRegistration

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Message-Id: <20250131-b4-rust_miscdevice_registrationdata-v2-0-588f1e6cfabe@gmail.com>
Date: Fri, 31 Jan 2025 16:08:13 +0100
From: Christian Schrefl <chrisi.schrefl@...il.com>
To: Miguel Ojeda <ojeda@...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>, 
 Benno Lossin <benno.lossin@...ton.me>, 
 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>, 
 Danilo Krummrich <dakr@...nel.org>
Cc: rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Christian Schrefl <chrisi.schrefl@...il.com>
Subject: [PATCH v2 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 adds the UnsafePinned (Previously Aliased) type.

The second patch implements the changes and fixes the build of the sample.

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
(Thanks a lot to everyone helping me out with this):
Link: https://rust-for-linux.zulipchat.com/#narrow/channel/288089-General/topic/Passing.20a.20DevRes.20to.20a.20miscdev/near/494553814

Signed-off-by: Christian Schrefl <chrisi.schrefl@...il.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 befofre `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: add UnsafePinned type
      rust: miscdevice: Add additional data to MiscDeviceRegistration
      rust: miscdevice: adjust the rust_misc_device sample to use RegistrationData.

 rust/kernel/miscdevice.rs        |  75 ++++++++++++++++++-------
 rust/kernel/types.rs             |  57 +++++++++++++++++++
 samples/rust/rust_misc_device.rs | 117 ++++++++++++++++++++++++++++++++++++---
 3 files changed, 221 insertions(+), 28 deletions(-)
---
base-commit: b4b0881156fb8209bf5ef6cb63211bb0ad6e1a6b
change-id: 20250119-b4-rust_miscdevice_registrationdata-a11d88dcb284

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