Re: [PATCH v26 3/4] rust: leds: Add multicolor classdev abstractions

[Boqun Feng <boqun@kernel.org>]

On Wed, Sep 30, 2026 at 01:05:32PM +0000, Markus Probst wrote:
> Implement the abstractions needed for multicolor led class devices,
> including:
> 
> * `led::MultiColor` - the led mode implementation
> 
> * `MultiColorSubLed` - a safe wrapper arround `mc_subled`
> 
> * `led::MultiColorDevice` - a safe wrapper around `led_classdev_mc`
> 
> * `led::DeviceBuilder::build_multicolor` - a function to register a new
>   multicolor led class device
> 
> Signed-off-by: Markus Probst <markus.probst@posteo.de>
> ---
>  rust/bindings/bindings_helper.h |   1 +
>  rust/kernel/led.rs              |  34 ++-
>  rust/kernel/led/multicolor.rs   | 445 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 479 insertions(+), 1 deletion(-)
> 
> diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
> index 4b31aa7f432f..81a03985322a 100644
> --- a/rust/bindings/bindings_helper.h
> +++ b/rust/bindings/bindings_helper.h
> @@ -69,6 +69,7 @@
>  #include <linux/iosys-map.h>
>  #include <linux/jiffies.h>
>  #include <linux/jump_label.h>
> +#include <linux/led-class-multicolor.h>
>  #include <linux/mdio.h>
>  #include <linux/mm.h>
>  #include <linux/miscdevice.h>
> diff --git a/rust/kernel/led.rs b/rust/kernel/led.rs
> index c17f8ef75006..4b66fe41a80c 100644
> --- a/rust/kernel/led.rs
> +++ b/rust/kernel/led.rs
> @@ -30,8 +30,16 @@
>      types::Opaque, //
>  };
>  
> +#[cfg(CONFIG_LEDS_CLASS_MULTICOLOR)]
> +mod multicolor;
>  mod normal;
>  
> +#[cfg(CONFIG_LEDS_CLASS_MULTICOLOR)]
> +pub use multicolor::{
> +    MultiColor,
> +    MultiColorDevice,
> +    MultiColorSubLed, //
> +};
>  pub use normal::{
>      Device,
>      Normal, //
> @@ -233,7 +241,24 @@ pub enum Color {
>      Violet = bindings::LED_COLOR_ID_VIOLET,
>      Yellow = bindings::LED_COLOR_ID_YELLOW,
>      Ir = bindings::LED_COLOR_ID_IR,
> +    #[cfg_attr(
> +        CONFIG_LEDS_CLASS_MULTICOLOR,
> +        doc = "Use this color for a [`MultiColor`] led."
> +    )]
> +    #[cfg_attr(
> +        not(CONFIG_LEDS_CLASS_MULTICOLOR),
> +        doc = "Use this color for a `MultiColor` led."
> +    )]
> +    /// If the led supports RGB, use [`Color::Rgb`] instead.
>      Multi = bindings::LED_COLOR_ID_MULTI,
> +    #[cfg_attr(
> +        CONFIG_LEDS_CLASS_MULTICOLOR,
> +        doc = "Use this color for a [`MultiColor`] led with rgb support."
> +    )]
> +    #[cfg_attr(
> +        not(CONFIG_LEDS_CLASS_MULTICOLOR),
> +        doc = "Use this color for a `MultiColor` led with rgb support."
> +    )]
>      Rgb = bindings::LED_COLOR_ID_RGB,
>      Purple = bindings::LED_COLOR_ID_PURPLE,
>      Orange = bindings::LED_COLOR_ID_ORANGE,
> @@ -274,7 +299,14 @@ fn try_from(value: u32) -> core::result::Result<Self, Self::Error> {
>  ///
>  /// Each led mode has its own led class device type with different capabilities.
>  ///
> -/// See [`Normal`].
> +#[cfg_attr(
> +    CONFIG_LEDS_CLASS_MULTICOLOR,
> +    doc = "See [`Normal`] and [`MultiColor`]."
> +)]
> +#[cfg_attr(
> +    not(CONFIG_LEDS_CLASS_MULTICOLOR),
> +    doc = "See [`Normal`] and `MultiColor`."
> +)]
>  pub trait Mode: private::Sealed {
>      /// The class device for the led mode.
>      type Device<'bound, T: LedOps<Mode = Self> + 'bound>: Deref<Target = T>;
> diff --git a/rust/kernel/led/multicolor.rs b/rust/kernel/led/multicolor.rs
> new file mode 100644
> index 000000000000..309487bdf38a
> --- /dev/null
> +++ b/rust/kernel/led/multicolor.rs
> @@ -0,0 +1,445 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Led mode for the `struct led_classdev_mc`.
> +//!
> +//! C header: [`include/linux/led-class-multicolor.h`](srctree/include/linux/led-class-multicolor.h)
> +
> +use core::{
> +    cell::UnsafeCell,
> +    num::NonZero,
> +    ptr, //
> +};
> +
> +use crate::types::ScopeGuard;
> +
> +use super::*;
> +
> +/// The led mode for the `struct led_classdev_mc`. Leds with this mode can have multiple colors.
> +pub enum MultiColor {}
> +impl Mode for MultiColor {
> +    type Device<'bound, T: LedOps<Mode = Self> + 'bound> = MultiColorDevice<'bound, T>;
> +}
> +impl private::Sealed for MultiColor {}
> +
> +/// The multicolor sub led info representation.
> +///
> +/// This structure represents the Rust abstraction for a C `struct mc_subled`.
> +#[repr(C)]
> +#[derive(Debug)]
> +#[non_exhaustive]
> +pub struct MultiColorSubLed {
> +    /// The color of the sub led
> +    pub color: Color,
> +    brightness: UnsafeCell<u32>,
> +    intensity: UnsafeCell<u32>,

These should be `Atomic<u32>`, or am I missing something here? Using
`Atomic<u32>` should resolve sashiko's comment on this patch.

Regards,
Boqun

> +    /// The maximum supported intensity value.
> +    ///
> +    /// If None the maximum intensity equals to [`LedOps::MAX_BRIGHTNESS`].
> +    pub max_intensity: Option<NonZero<u32>>,
> +    /// Arbitrary data for the driver to store.
> +    pub channel: u32,
> +}
> +
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