Re: [PATCH 6/7] rust: miscdevice: expose the parent device as &Device<Bound>

["Benno Lossin" <lossin@kernel.org>]

On Fri May 30, 2025 at 4:24 PM CEST, Danilo Krummrich wrote:
> @@ -227,11 +229,21 @@ fn drop(self: Pin<&mut Self>) {
>      }
>  }
>  
> +/// The arguments passed to the file operation callbacks of a [`MiscDeviceRegistration`].
> +pub struct MiscArgs<'a, T: MiscDevice> {
> +    /// The [`Device`] representation of the `struct miscdevice`.
> +    pub device: &'a Device,
> +    /// The parent [`Device`] of [`Self::device`].
> +    pub parent: Option<&'a Device<Bound>>,
> +    /// The `RegistrationData` passed to [`MiscDeviceRegistration::register`].
> +    pub data: &'a T::RegistrationData,

Here I would also just use `T`, remove the `MiscDevice` bound and then
use `MiscArgs<'_, Self::RegistrationData>` below.

> +}
> +
>  /// Trait implemented by the private data of an open misc device.
>  #[vtable]
>  pub trait MiscDevice: Sized {
>      /// What kind of pointer should `Self` be wrapped in.
> -    type Ptr: ForeignOwnable + Send + Sync;
> +    type Ptr: Send + Sync;

There is no info about this change in the commit message. Why are we
changing this? This seems a bit orthogonal to the other change, maybe do
it in a separate patch?

Also `Ptr` doesn't make much sense for the name, since now that the
`ForeignOwnable` bound is gone, I could set this to `Self` and then have
access to `&Self` in the callbacks.

Would that also make sense to use as a general change? So don't store
`Self::Ptr`, but `Self` directly?

---
Cheers,
Benno