linux-kernel - [PATCH v11 1/3] pwm: Export `pwmchip

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Message-Id: <20250710-rust-next-pwm-working-fan-for-sending-v11-1-93824a16f9ec@samsung.com>
Date: Thu, 10 Jul 2025 20:54:28 +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>, Drew Fustini <drew@...7.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>, Benno Lossin <lossin@...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 v11 1/3] 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 | 5 +++++
 2 files changed, 7 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..8f0698c09e62b893d63fc258da3c34781183056f 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -478,6 +478,7 @@ static inline bool pwm_might_sleep(struct pwm_device *pwm)
 
 /* PWM provider APIs */
 void pwmchip_put(struct pwm_chip *chip);
+void pwmchip_release(struct device *dev);
 struct pwm_chip *pwmchip_alloc(struct device *parent, unsigned int npwm, size_t sizeof_priv);
 struct pwm_chip *devm_pwmchip_alloc(struct device *parent, unsigned int npwm, size_t sizeof_priv);
 
@@ -551,6 +552,10 @@ static inline void pwmchip_put(struct pwm_chip *chip)
 {
 }
 
+static inline void pwmchip_release(struct device *dev)
+{
+}
+
 static inline struct pwm_chip *pwmchip_alloc(struct device *parent,
 					     unsigned int npwm,
 					     size_t sizeof_priv)

-- 
2.34.1