linux-kernel - Re: [RFC PATCH 02/11] rust: add driver abstraction

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Date: Wed, 29 May 2024 13:10:50 +0200
From: Dirk Behme <dirk.behme@...bosch.com>
To: Danilo Krummrich <dakr@...hat.com>, <gregkh@...uxfoundation.org>,
	<rafael@...nel.org>, <bhelgaas@...gle.com>, <ojeda@...nel.org>,
	<alex.gaynor@...il.com>, <wedsonaf@...il.com>, <boqun.feng@...il.com>,
	<gary@...yguo.net>, <bjorn3_gh@...tonmail.com>, <benno.lossin@...ton.me>,
	<a.hindborg@...sung.com>, <aliceryhl@...gle.com>, <airlied@...il.com>,
	<fujita.tomonori@...il.com>, <lina@...hilina.net>, <pstanner@...hat.com>,
	<ajanulgu@...hat.com>, <lyude@...hat.com>
CC: <rust-for-linux@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-pci@...r.kernel.org>
Subject: Re: [RFC PATCH 02/11] rust: add driver abstraction

On 20.05.2024 19:25, Danilo Krummrich wrote:
> From: Wedson Almeida Filho <wedsonaf@...il.com>
> 
> This defines general functionality related to registering drivers with
> their respective subsystems, and registering modules that implement
> drivers.
> 
> Co-developed-by: Asahi Lina <lina@...hilina.net>
> Signed-off-by: Asahi Lina <lina@...hilina.net>
> Co-developed-by: Andreas Hindborg <a.hindborg@...sung.com>
> Signed-off-by: Andreas Hindborg <a.hindborg@...sung.com>
> Signed-off-by: Wedson Almeida Filho <wedsonaf@...il.com>
> Signed-off-by: Danilo Krummrich <dakr@...hat.com>
> ---
>   rust/kernel/driver.rs        | 492 +++++++++++++++++++++++++++++++++++
>   rust/kernel/lib.rs           |   4 +-
>   rust/macros/module.rs        |   2 +-
>   samples/rust/rust_minimal.rs |   2 +-
>   samples/rust/rust_print.rs   |   2 +-
>   5 files changed, 498 insertions(+), 4 deletions(-)
>   create mode 100644 rust/kernel/driver.rs
> 
> diff --git a/rust/kernel/driver.rs b/rust/kernel/driver.rs
> new file mode 100644
> index 000000000000..e0cfc36d47ff
> --- /dev/null
> +++ b/rust/kernel/driver.rs
> @@ -0,0 +1,492 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Generic support for drivers of different buses (e.g., PCI, Platform, Amba, etc.).
> +//!
> +//! Each bus/subsystem is expected to implement [`DriverOps`], which allows drivers to register
> +//! using the [`Registration`] class.
> +
> +use crate::{
> +    alloc::{box_ext::BoxExt, flags::*},
> +    error::code::*,
> +    error::Result,
> +    str::CStr,
> +    sync::Arc,
> +    ThisModule,
> +};
> +use alloc::boxed::Box;
> +use core::{cell::UnsafeCell, marker::PhantomData, ops::Deref, pin::Pin};
> +
> +/// A subsystem (e.g., PCI, Platform, Amba, etc.) that allows drivers to be written for it.
> +pub trait DriverOps {
> +    /// The type that holds information about the registration. This is typically a struct defined
> +    /// by the C portion of the kernel.
> +    type RegType: Default;
> +
> +    /// Registers a driver.
> +    ///
> +    /// # Safety
> +    ///
> +    /// `reg` must point to valid, initialised, and writable memory. It may be modified by this
> +    /// function to hold registration state.
> +    ///
> +    /// On success, `reg` must remain pinned and valid until the matching call to
> +    /// [`DriverOps::unregister`].
> +    unsafe fn register(
> +        reg: *mut Self::RegType,
> +        name: &'static CStr,
> +        module: &'static ThisModule,
> +    ) -> Result;
> +
> +    /// Unregisters a driver previously registered with [`DriverOps::register`].
> +    ///
> +    /// # Safety
> +    ///
> +    /// `reg` must point to valid writable memory, initialised by a previous successful call to
> +    /// [`DriverOps::register`].
> +    unsafe fn unregister(reg: *mut Self::RegType);
> +}
> +
> +/// The registration of a driver.
> +pub struct Registration<T: DriverOps> {
> +    is_registered: bool,
> +    concrete_reg: UnsafeCell<T::RegType>,
> +}
> +
> +// SAFETY: `Registration` has no fields or methods accessible via `&Registration`, so it is safe to
> +// share references to it with multiple threads as nothing can be done.
> +unsafe impl<T: DriverOps> Sync for Registration<T> {}


You might want to check if we additionally need 'Send' due to

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=323617f649c0966ad5e741e47e27e06d3a680d8f

here?

+ unsafe impl<T: DriverOps> Send for Registration<T> {}

This was found re-basing

https://github.com/Rust-for-Linux/linux/commits/staging/rust-device/

to v6.10-rc1.

Sorry if I missed anything ;)

Best regards

Dirk