[PATCH v25 2/4] rust: leds: add Mode trait

[Markus Probst <markus.probst@posteo.de>]

Add the `led::Mode` trait to allow for other types of led class devices
in `led::LedOps`.

Signed-off-by: Markus Probst <markus.probst@posteo.de>
---
 rust/kernel/led.rs        | 37 ++++++++++++++++++++++++++-----------
 rust/kernel/led/normal.rs | 12 ++++++++++--
 2 files changed, 36 insertions(+), 13 deletions(-)

diff --git a/rust/kernel/led.rs b/rust/kernel/led.rs
index deda8cc548a8..7cd8f0504649 100644
--- a/rust/kernel/led.rs
+++ b/rust/kernel/led.rs
@@ -4,11 +4,7 @@
 //!
 //! C header: [`include/linux/leds.h`](srctree/include/linux/leds.h)
 
-use core::{
-    marker::PhantomData,
-    mem::transmute,
-    ptr::NonNull, //
-};
+use core::{marker::PhantomData, mem::transmute, ops::Deref, ptr::NonNull};
 
 use crate::{
     container_of,
@@ -31,7 +27,10 @@
 
 mod normal;
 
-pub use normal::Device;
+pub use normal::{
+    Device,
+    Normal, //
+};
 
 /// The name of the led is determined by the driver.
 pub enum Named {}
@@ -156,6 +155,7 @@ pub fn name(self, name: &'init CStr) -> Self {
 ///
 /// #[vtable]
 /// impl led::LedOps for MyLedOps {
+///     type Mode = led::Normal;
 ///     const BLOCKING: bool = false;
 ///     const MAX_BRIGHTNESS: u32 = 255;
 ///
@@ -176,16 +176,21 @@ pub trait LedOps: Send + Sync + Sized {
     const BLOCKING: bool;
     /// The max brightness level.
     const MAX_BRIGHTNESS: u32;
-
     /// Sets the brightness level.
     ///
     /// See also [`LedOps::BLOCKING`].
-    fn brightness_set<'bound>(self: &Device<'bound, Self>, brightness: u32) -> Result<()>;
-
+    fn brightness_set<'bound>(
+        self: &<Self::Mode as Mode>::Device<'bound, Self>,
+        brightness: u32,
+    ) -> Result<()>;
     /// Gets the current brightness level.
-    fn brightness_get<'bound>(self: &Device<'bound, Self>) -> Result<u32> {
+    fn brightness_get<'bound>(self: &<Self::Mode as Mode>::Device<'bound, Self>) -> Result<u32> {
         build_error!(VTABLE_DEFAULT_ERROR)
     }
+    /// The led mode to use.
+    ///
+    /// See [`Mode`].
+    type Mode: Mode;
 
     /// Activates hardware accelerated blinking.
     ///
@@ -196,7 +201,7 @@ fn brightness_get<'bound>(self: &Device<'bound, Self>) -> Result<u32> {
     ///
     /// See also [`LedOps::BLOCKING`].
     fn blink_set<'bound>(
-        self: &Device<'bound, Self>,
+        self: &<Self::Mode as Mode>::Device<'bound, Self>,
         delay_on: &mut usize,
         delay_off: &mut usize,
     ) -> Result<()> {
@@ -260,6 +265,16 @@ fn try_from(value: u32) -> core::result::Result<Self, Self::Error> {
     }
 }
 
+/// The led mode.
+///
+/// Each led mode has its own led class device type with different capabilities.
+///
+/// See [`Normal`].
+pub trait Mode: private::Sealed {
+    /// The class device for the led mode.
+    type Device<'bound, T: LedOps<Mode = Self> + 'bound>: Deref<Target = T>;
+}
+
 mod private {
     pub trait Sealed {}
 }
diff --git a/rust/kernel/led/normal.rs b/rust/kernel/led/normal.rs
index a22c29cfd262..992353319522 100644
--- a/rust/kernel/led/normal.rs
+++ b/rust/kernel/led/normal.rs
@@ -8,6 +8,14 @@
 
 use super::*;
 
+/// The led mode for the `struct led_classdev`. Leds with this mode can only have a fixed color.
+pub enum Normal {}
+
+impl Mode for Normal {
+    type Device<'bound, T: LedOps<Mode = Self> + 'bound> = Device<'bound, T>;
+}
+impl private::Sealed for Normal {}
+
 /// The led class device representation.
 ///
 /// This structure represents the Rust abstraction for a led class device.
@@ -22,7 +30,7 @@ pub struct Device<'bound, T: 'bound = ()> {
 
 impl<'init, S: DeviceBuilderState> DeviceBuilder<'init, S> {
     /// Registers a new [`Device`].
-    pub fn build<'bound: 'init, T: LedOps + 'bound>(
+    pub fn build<'bound: 'init, T: LedOps<Mode = Normal> + 'bound>(
         self,
         parent: &'bound device::Device<Bound>,
         ops: impl PinInit<T, Error> + 'init,
@@ -120,7 +128,7 @@ struct Adapter<T: LedOps> {
     _p: PhantomData<T>,
 }
 
-impl<T: LedOps> Adapter<T> {
+impl<T: LedOps<Mode = Normal>> Adapter<T> {
     /// # Safety
     /// `led_cdev` must be a valid pointer to a `led_classdev` embedded within a
     /// `led::Device`.

-- 
2.55.0