[PATCH v14 2/7] rust: pwm: Add Kconfig and basic data structures

[Michal Wilczynski <m.wilczynski@samsung.com>]

Introduce the foundational support for PWM abstractions in Rust.

This commit adds the `RUST_PWM_ABSTRACTIONS` Kconfig option to enable
the feature, along with the necessary build-system support and C
helpers.

It also introduces the first set of safe wrappers for the PWM
subsystem, covering the basic data carrying C structs and enums:
- `Polarity`: A safe wrapper for `enum pwm_polarity`.
- `Waveform`: A wrapper for `struct pwm_waveform`.
- `Args`: A wrapper for `struct pwm_args`.
- `State`: A wrapper for `struct pwm_state`.

These types provide memory safe, idiomatic Rust representations of the
core PWM data structures and form the building blocks for the
abstractions that will follow.

Tested-by: Drew Fustini <fustini@kernel.org>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Michal Wilczynski <m.wilczynski@samsung.com>
---
 MAINTAINERS                     |   8 +++
 drivers/pwm/Kconfig             |  13 +++++
 rust/bindings/bindings_helper.h |   1 +
 rust/helpers/helpers.c          |   1 +
 rust/helpers/pwm.c              |  20 +++++++
 rust/kernel/lib.rs              |   2 +
 rust/kernel/pwm.rs              | 123 ++++++++++++++++++++++++++++++++++++++++
 7 files changed, 168 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index fe168477caa45799dfe07de2f54de6d6a1ce0615..5d7c0676c1d00a02b3d7db2de88b039c08c99c6e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -20387,6 +20387,14 @@ F:	include/linux/pwm.h
 F:	include/linux/pwm_backlight.h
 K:	pwm_(config|apply_might_sleep|apply_atomic|ops)
 
+PWM SUBSYSTEM BINDINGS [RUST]
+M:	Michal Wilczynski <m.wilczynski@samsung.com>
+L:	linux-pwm@vger.kernel.org
+L:	rust-for-linux@vger.kernel.org
+S:	Maintained
+F:	rust/helpers/pwm.c
+F:	rust/kernel/pwm.rs
+
 PXA GPIO DRIVER
 M:	Robert Jarzmik <robert.jarzmik@free.fr>
 L:	linux-gpio@vger.kernel.org
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index f00ce973dddf651287168b44228574f4d5c28dc0..2b608f4378138775ee3ba4d53f682952e1914118 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -800,4 +800,17 @@ config PWM_XILINX
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-xilinx.
 
+ config RUST_PWM_ABSTRACTIONS
+	bool "Rust PWM abstractions support"
+	depends on RUST
+	depends on PWM=y
+	help
+	  This option enables the safe Rust abstraction layer for the PWM
+	  subsystem. It provides idiomatic wrappers and traits necessary for
+	  writing PWM controller drivers in Rust.
+
+	  The abstractions handle resource management (like memory and reference
+	  counting) and provide safe interfaces to the underlying C core,
+	  allowing driver logic to be written in safe Rust.
+
 endif
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 84d60635e8a9baef1f1a1b2752dc0fa044f8542f..7a06ee5781eadc9f21ccd456b574a9cb152cd58c 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -66,6 +66,7 @@
 #include <linux/pm_opp.h>
 #include <linux/poll.h>
 #include <linux/property.h>
+#include <linux/pwm.h>
 #include <linux/refcount.h>
 #include <linux/regulator/consumer.h>
 #include <linux/sched.h>
diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
index 7cf7fe95e41dd51717050648d6160bebebdf4b26..861052ffffaff60e9c2e8109e55f3b6158ff2281 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -35,6 +35,7 @@
 #include "platform.c"
 #include "poll.c"
 #include "property.c"
+#include "pwm.c"
 #include "rbtree.c"
 #include "rcu.c"
 #include "refcount.c"
diff --git a/rust/helpers/pwm.c b/rust/helpers/pwm.c
new file mode 100644
index 0000000000000000000000000000000000000000..d75c588863685d3990b525bb1b84aa4bc35ac397
--- /dev/null
+++ b/rust/helpers/pwm.c
@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2025 Samsung Electronics Co., Ltd.
+// Author: Michal Wilczynski <m.wilczynski@samsung.com>
+
+#include <linux/pwm.h>
+
+struct device *rust_helper_pwmchip_parent(const struct pwm_chip *chip)
+{
+	return pwmchip_parent(chip);
+}
+
+void *rust_helper_pwmchip_get_drvdata(struct pwm_chip *chip)
+{
+	return pwmchip_get_drvdata(chip);
+}
+
+void rust_helper_pwmchip_set_drvdata(struct pwm_chip *chip, void *data)
+{
+	pwmchip_set_drvdata(chip, data);
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index ed53169e795c0badf548025a57f946fa18bc73e3..e339b552f9650803b1efa1eb8ecc6fe9d2c56563 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -117,6 +117,8 @@
 pub mod seq_file;
 pub mod sizes;
 mod static_assert;
+#[cfg(CONFIG_RUST_PWM_ABSTRACTIONS)]
+pub mod pwm;
 #[doc(hidden)]
 pub mod std_vendor;
 pub mod str;
diff --git a/rust/kernel/pwm.rs b/rust/kernel/pwm.rs
new file mode 100644
index 0000000000000000000000000000000000000000..57675a3dfca12033355670deb210ca66f8469334
--- /dev/null
+++ b/rust/kernel/pwm.rs
@@ -0,0 +1,123 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2025 Samsung Electronics Co., Ltd.
+// Author: Michal Wilczynski <m.wilczynski@samsung.com>
+
+//! PWM subsystem abstractions.
+//!
+//! C header: [`include/linux/pwm.h`](srctree/include/linux/pwm.h).
+
+use crate::{
+    bindings,
+    prelude::*,
+    types::Opaque,
+};
+use core::convert::TryFrom;
+
+/// PWM polarity. Mirrors [`enum pwm_polarity`](srctree/include/linux/pwm.h).
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum Polarity {
+    /// Normal polarity (duty cycle defines the high period of the signal).
+    Normal,
+
+    /// Inversed polarity (duty cycle defines the low period of the signal).
+    Inversed,
+}
+
+impl TryFrom<bindings::pwm_polarity> for Polarity {
+    type Error = Error;
+
+    fn try_from(polarity: bindings::pwm_polarity) -> Result<Self, Error> {
+        match polarity {
+            bindings::pwm_polarity_PWM_POLARITY_NORMAL => Ok(Polarity::Normal),
+            bindings::pwm_polarity_PWM_POLARITY_INVERSED => Ok(Polarity::Inversed),
+            _ => Err(EINVAL),
+        }
+    }
+}
+
+impl From<Polarity> for bindings::pwm_polarity {
+    fn from(polarity: Polarity) -> Self {
+        match polarity {
+            Polarity::Normal => bindings::pwm_polarity_PWM_POLARITY_NORMAL,
+            Polarity::Inversed => bindings::pwm_polarity_PWM_POLARITY_INVERSED,
+        }
+    }
+}
+
+/// Represents a PWM waveform configuration.
+/// Mirrors struct [`struct pwm_waveform`](srctree/include/linux/pwm.h).
+#[derive(Copy, Clone, Debug, Default, PartialEq, Eq)]
+pub struct Waveform {
+    /// Total duration of one complete PWM cycle, in nanoseconds.
+    pub period_length_ns: u64,
+
+    /// Duty-cycle active time, in nanoseconds.
+    ///
+    /// For a typical normal polarity configuration (active-high) this is the
+    /// high time of the signal.
+    pub duty_length_ns: u64,
+
+    /// Duty-cycle start offset, in nanoseconds.
+    ///
+    /// Delay from the beginning of the period to the first active edge.
+    /// In most simple PWM setups this is `0`, so the duty cycle starts
+    /// immediately at each period’s start.
+    pub duty_offset_ns: u64,
+}
+
+impl From<bindings::pwm_waveform> for Waveform {
+    fn from(wf: bindings::pwm_waveform) -> Self {
+        Waveform {
+            period_length_ns: wf.period_length_ns,
+            duty_length_ns: wf.duty_length_ns,
+            duty_offset_ns: wf.duty_offset_ns,
+        }
+    }
+}
+
+impl From<Waveform> for bindings::pwm_waveform {
+    fn from(wf: Waveform) -> Self {
+        bindings::pwm_waveform {
+            period_length_ns: wf.period_length_ns,
+            duty_length_ns: wf.duty_length_ns,
+            duty_offset_ns: wf.duty_offset_ns,
+        }
+    }
+}
+
+/// Wrapper for board-dependent PWM arguments [`struct pwm_args`](srctree/include/linux/pwm.h).
+#[repr(transparent)]
+pub struct Args(bindings::pwm_args);
+
+impl Args {
+    /// Creates a `Args` wrapper by taking ownership of a C `pwm_args` value.
+    pub(crate) fn from_c(c_args: bindings::pwm_args) -> Self {
+        Args(c_args)
+    }
+
+    /// Returns the period of the PWM signal in nanoseconds.
+    pub fn period(&self) -> u64 {
+        self.0.period
+    }
+
+    /// Returns the polarity of the PWM signal.
+    pub fn polarity(&self) -> Result<Polarity, Error> {
+        Polarity::try_from(self.0.polarity)
+    }
+}
+
+/// Wrapper for PWM state [`struct pwm_state`](srctree/include/linux/pwm.h).
+#[repr(transparent)]
+pub struct State(bindings::pwm_state);
+
+impl State {
+    /// Creates a `State` wrapper by taking ownership of a C `pwm_state` value.
+    pub(crate) fn from_c(c_state: bindings::pwm_state) -> Self {
+        State(c_state)
+    }
+
+    /// Returns `true` if the PWM signal is enabled.
+    pub fn enabled(&self) -> bool {
+        self.0.enabled
+    }
+}

-- 
2.34.1