linux-kernel - [PATCH v14 1/7] pwm: Export `pwmchip

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Message-Id: <20250820-rust-next-pwm-working-fan-for-sending-v14-1-df2191621429@samsung.com>
Date: Wed, 20 Aug 2025 10:35:36 +0200
From: Michal Wilczynski <m.wilczynski@...sung.com>
To: Uwe Kleine-König <ukleinek@...nel.org>,  Miguel Ojeda
	<ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,  Boqun Feng
	<boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, 
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,  Andreas
	Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>,  Trevor
	Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>,  Michal
	Wilczynski <m.wilczynski@...sung.com>, Guo Ren <guoren@...nel.org>,  Fu Wei
	<wefu@...hat.com>, Rob Herring <robh@...nel.org>,  Krzysztof Kozlowski
	<krzk+dt@...nel.org>,  Conor Dooley <conor+dt@...nel.org>,  Paul Walmsley
	<paul.walmsley@...ive.com>,  Palmer Dabbelt <palmer@...belt.com>, Albert Ou
	<aou@...s.berkeley.edu>,  Alexandre Ghiti <alex@...ti.fr>,  Marek Szyprowski
	<m.szyprowski@...sung.com>,  Benno Lossin <lossin@...nel.org>,  Michael
	Turquette <mturquette@...libre.com>,  Drew Fustini <fustini@...nel.org>, 
	Daniel Almeida <daniel.almeida@...labora.com>,  Benno Lossin
	<lossin@...nel.org>, Drew Fustini <fustini@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-pwm@...r.kernel.org,
	rust-for-linux@...r.kernel.org, linux-riscv@...ts.infradead.org, 
	devicetree@...r.kernel.org
Subject: [PATCH v14 1/7] pwm: Export `pwmchip_release` for external use

The upcoming Rust abstraction layer for the PWM subsystem uses a custom
`dev->release` handler to safely manage the lifetime of its driver
data.

To prevent leaking the memory of the `struct pwm_chip` (allocated by
`pwmchip_alloc`), this custom handler must also call the original
`pwmchip_release` function to complete the cleanup.

Make `pwmchip_release` a global, exported function so that it can be
called from the Rust FFI bridge. This involves removing the `static`
keyword, adding a prototype to the public header, and exporting the
symbol.

Signed-off-by: Michal Wilczynski <m.wilczynski@...sung.com>
---
 drivers/pwm/core.c  | 3 ++-
 include/linux/pwm.h | 6 ++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 0d66376a83ec350e0c3718959f4d794efd71595a..a33da3dff608fdff91251e5fd07b0dbd295be022 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -1600,12 +1600,13 @@ void pwmchip_put(struct pwm_chip *chip)
 }
 EXPORT_SYMBOL_GPL(pwmchip_put);
 
-static void pwmchip_release(struct device *pwmchip_dev)
+void pwmchip_release(struct device *pwmchip_dev)
 {
 	struct pwm_chip *chip = pwmchip_from_dev(pwmchip_dev);
 
 	kfree(chip);
 }
+EXPORT_SYMBOL_GPL(pwmchip_release);
 
 struct pwm_chip *pwmchip_alloc(struct device *parent, unsigned int npwm, size_t sizeof_priv)
 {
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 8cafc483db53addf95591d1ac74287532c0fa0ee..d86061024b52172edf3845bf9252a966f120e365 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -485,6 +485,12 @@ int __pwmchip_add(struct pwm_chip *chip, struct module *owner);
 #define pwmchip_add(chip) __pwmchip_add(chip, THIS_MODULE)
 void pwmchip_remove(struct pwm_chip *chip);
 
+/*
+ * For FFI wrapper use only:
+ * The Rust PWM abstraction needs this to properly free the pwm_chip.
+ */
+void pwmchip_release(struct device *dev);
+
 int __devm_pwmchip_add(struct device *dev, struct pwm_chip *chip, struct module *owner);
 #define devm_pwmchip_add(dev, chip) __devm_pwmchip_add(dev, chip, THIS_MODULE)
 

-- 
2.34.1