[PATCH v16 1/7] pwm: Export `pwmchip_release` for external use

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

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.

Reviewed-by: Elle Rhumsaa <elle@weathered-steel.dev>
Signed-off-by: Michal Wilczynski <m.wilczynski@samsung.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 ea2ccf42e81441d00a349f6d8641c92143d94797..47c9333baaf6c7d752a71c26bb1957ea2fd17a50 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -1608,12 +1608,13 @@ 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 549ac4aaad59ba6d7ba58d818b46a58a8759e09c..148f056f336bbe17ffc3df22aa6b6bc3ad854e40 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -488,6 +488,12 @@ 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