linux-kernel - [PATCH v12 1/3] pwm: Export `pwmchip

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Message-Id: <20250717-rust-next-pwm-working-fan-for-sending-v12-1-40f73defae0c@samsung.com>
Date: Thu, 17 Jul 2025 11:08:23 +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 v12 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 | 6 ++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 4d842c69219445ff1c97ebdb9f1f64031c183a84..bbf729b95c7b94b05bc25bdc1febafb0f2437121 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -1598,12 +1598,13 @@ 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 63a17d2b4ec8d0d34a02b05240efb75b637dd99f..82707802ff93432086e5a8f915b519b987c68041 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -480,6 +480,12 @@ 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