[RFC PATCH 7/8] rust: add firmware abstractions

[Danilo Krummrich]

On Thu, May 30, 2024 at 08:28:24AM +0900, FUJITA Tomonori wrote:
> Hi,
> 
> On Wed, 29 May 2024 21:57:03 +0200
> Greg KH <gregkh at linuxfoundation.org> wrote:
> 
> >> For a Rust PHY driver, you know that you have a valid pointer to C's
> >> device object of C's PHY device during the probe callback. The driver
> >> creates a Rust device object to wrap the C pointer to the C's device
> >> object and passes it to the firmware abstractions. The firmware
> >> abstractions gets the C's pointer from the Rust object and calls C's
> >> function to load firmware, returns the result.
> >> 
> >> You have concerns about the simple code like the following?
> >> 
> >> 
> >> diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
> >> new file mode 100644
> >> index 000000000000..6144437984a9
> >> --- /dev/null
> >> +++ b/rust/kernel/device.rs
> >> @@ -0,0 +1,30 @@
> >> +// SPDX-License-Identifier: GPL-2.0
> >> +
> >> +//! Generic devices that are part of the kernel's driver model.
> >> +//!
> >> +//! C header: [`include/linux/device.h`](srctree/include/linux/device.h)
> >> +
> >> +use crate::types::Opaque;
> >> +
> >> +#[repr(transparent)]
> >> +pub struct Device(Opaque<bindings::device>);
> >> +
> >> +impl Device {
> >> +    /// Creates a new [`Device`] instance from a raw pointer.
> >> +    ///
> >> +    /// # Safety
> >> +    ///
> >> +    /// For the duration of 'a, the pointer must point at a valid `device`.
> > 
> > If the following rust code does what this comment says, then sure, I'm
> > ok with it for now if it helps you all out with stuff like the firmware
> > interface for the phy rust code.
> 
> Great, thanks a lot!
> 
> Danilo and Wedson, are there any concerns about pushing this patch [1]
> for the firmware abstractions?

Well, if everyone is fine with this one I don't see why we can't we go with [1]
directly? AFAICS, we'd only need the following fix:

-//! C header: [`include/linux/device.h`](../../../../include/linux/device.h)
+//! C header: [`include/linux/device.h`](srctree/include/linux/device.h)

[1] https://lore.kernel.org/rust-for-linux/20240520172554.182094-2-dakr@redhat.com/

> 
> I you prefer to be the author of the patch, please let me know. Who
> the author is doesn't matter to me. Otherwise, I'll add
> Co-developed-by tag.
> 
> [1] https://lore.kernel.org/rust-for-linux/20240529.092821.1593412345609718860.fujita.tomonori@gmail.com/
>