linux-kernel - Re: [PATCH v7 0/2] rust: leds: add led classdev abstractions

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Message-ID: <ce0b823830c8477b723fb8d6ee0166e5b5848fa0.camel@posteo.de>
Date: Thu, 13 Nov 2025 14:17:36 +0000
From: Markus Probst <markus.probst@...teo.de>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Miguel Ojeda
	 <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, Danilo Krummrich
	 <dakr@...nel.org>, "Rafael J. Wysocki" <rafael@...nel.org>, Lee Jones
	 <lee@...nel.org>, Pavel Machek <pavel@...nel.org>
Cc: Dave Ertman <david.m.ertman@...el.com>, Ira Weiny <ira.weiny@...el.com>,
  Leon Romanovsky	 <leon@...nel.org>, Boqun Feng <boqun.feng@...il.com>,
 Gary Guo <gary@...yguo.net>, 	bjorn3_gh@...tonmail.com, Benno Lossin
 <lossin@...nel.org>, Andreas Hindborg	 <a.hindborg@...nel.org>, Alice Ryhl
 <aliceryhl@...gle.com>, Trevor Gross	 <tmgross@...ch.edu>, Bjorn Helgaas
 <bhelgaas@...gle.com>, Krzysztof Wilczyński	
 <kwilczynski@...nel.org>, rust-for-linux@...r.kernel.org, 
	linux-leds@...r.kernel.org, linux-pci@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 0/2] rust: leds: add led classdev abstractions

On Mon, 2025-10-27 at 20:06 +0000, Markus Probst wrote:
> This patch series has previously been contained in
> https://lore.kernel.org/rust-for-linux/20251008181027.662616-1-markus.probst@posteo.de/T/#t
> which added a rust written led driver for a microcontroller via i2c.
> 
> As the reading and writing to the i2c client via the register!
> macro has not been implemented yet [1], the patch series will only
> contain the additional abstractions required.
> 
> [1] https://lore.kernel.org/rust-for-linux/DDDS2V0V2NVJ.16ZKXCKUA1HUV@kernel.org/
> 
> The following changes were made:
> * add abstraction to convert a device reference to a bus device
>   reference for use in class device callbacks
> 
> * add basic led classdev abstractions to register and unregister leds
> 
> Changes since v6:
> * fixed typos
> * improved documentation
> 
> Changes since v5:
> * rename `IntoBusDevice` trait into `AsBusDevice`
> * fix documentation about `LedOps::BLOCKING`
> * removed dependency on i2c bindings
> * added `AsBusDevice` implementation for `platform::Device`
> * removed `device::Device` fallback implementation
> * document that `AsBusDevice` must not be used by drivers and is
>   intended for bus and class device abstractions only.
> 
> Changes since v4:
> * add abstraction to convert a device reference to a bus device
>   reference
> * require the bus device as parent device and provide it in class device
>   callbacks
> * remove Pin<Vec<_>> abstraction (as not relevant for the led
>   abstractions)
> * fixed formatting in `led::Device::new`
> * fixed `LedOps::BLOCKING` did the inverse effect
> 
> Changes since v3:
> * fixed kunit tests failing because of example in documentation
> 
> Changes since v2:
> * return `Devres` on `led::Device` creation
> * replace KBox<T> with T in struct definition
> * increment and decrement reference-count of fwnode
> * make a device parent mandatory for led classdev creation
> * rename `led::Handler` to `led::LedOps`
> * add optional `brightness_get` function to `led::LedOps`
> * use `#[vtable]` instead of `const BLINK: bool`
> * use `Opaque::cast_from` instead of casting a pointer
> * improve documentation
> * improve support for older rust versions
> * use `&Device<Bound>` for parent
> 
> Changes since v1:
> * fixed typos noticed by Onur Özkan
> 
> Markus Probst (2):
>   rust: Add trait to convert a device reference to a bus device
>     reference
>   rust: leds: add basic led classdev abstractions
> 
> Markus Probst (2):
>   rust: Add trait to convert a device reference to a bus device
>     reference
>   rust: leds: add basic led classdev abstractions

Hi,

So you know in advance, I will add a 3. patch for multicolor led
classdev abstractions (drivers/leds/led-class-multicolor.c,
include/linux/led-class-multicolor.h) to this patch series.

In the atmega1608 led driver (the user of these abstractions) there are
leds with different colors that share the same slot.
Technically "drivers/leds/rgb/leds-group-multicolor.c" could be used in
combination with single color leds instead, but then hardware
accelerated blinking wouldn't be supported. I think it would make more
sense to directly implement it in the driver.

The existing 2 patches shouldn't change, so feel free to review them.

Thanks
- Markus Probst

> 
>  rust/kernel/auxiliary.rs |   7 +
>  rust/kernel/device.rs    |  33 ++++
>  rust/kernel/led.rs       | 375 +++++++++++++++++++++++++++++++++++++++
>  rust/kernel/lib.rs       |   1 +
>  rust/kernel/pci.rs       |   7 +
>  rust/kernel/platform.rs  |   7 +
>  rust/kernel/usb.rs       |   6 +
>  7 files changed, 436 insertions(+)
>  create mode 100644 rust/kernel/led.rs