Re: [PATCH 4/4] rust: platform: fix unrestricted &mut platform::Device

[Benno Lossin]

On Thu Mar 13, 2025 at 3:13 AM CET, Danilo Krummrich wrote:
> As by now, platform::Device is implemented as:
>
> 	#[derive(Clone)]
> 	pub struct Device(ARef<device::Device>);
>
> This may be convenient, but has the implication that drivers can call
> device methods that require a mutable reference concurrently at any
> point of time.

Similar to the other patch, I didn't find any methods taking `&mut self`
but I might have missed them.

> Instead define platform::Device as
>
> 	pub struct Device<Ctx: DeviceContext = Normal>(
> 		Opaque<bindings::platform_dev>,
> 		PhantomData<Ctx>,
> 	);
>
> and manually implement the AlwaysRefCounted trait.
>
> With this we can implement methods that should only be called from
> bus callbacks (such as probe()) for platform::Device<Core>. Consequently,
> we make this type accessible in bus callbacks only.
>
> Arbitrary references taken by the driver are still of type
> ARef<platform::Device> and hence don't provide access to methods that are
> reserved for bus callbacks.
>
> Fixes: 683a63befc73 ("rust: platform: add basic platform device / driver abstractions")
> Signed-off-by: Danilo Krummrich <dakr@xxxxxxxxxx>

The same two nits from patch #3 also apply.

Reviewed-by: Benno Lossin <benno.lossin@xxxxxxxxx>

---
Cheers,
Benno

> ---
>  rust/kernel/platform.rs              | 93 ++++++++++++++++++----------
>  samples/rust/rust_driver_platform.rs | 16 +++--
>  2 files changed, 74 insertions(+), 35 deletions(-)