Commit ee37bf50 authored by Uwe Kleine-König's avatar Uwe Kleine-König
Browse files

pwm: Ensure a struct pwm has the same lifetime as its pwm_chip 

It's required to not free the memory underlying a requested PWM
while a consumer still has a reference to it. While currently a pwm_chip
doesn't live long enough in all cases, linking the struct pwm to the
pwm_chip results in the right lifetime as soon as the pwmchip is living
long enough. This happens with the following commits.

Note this is a breaking change for all pwm drivers that don't use
pwmchip_alloc().

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org> # for struct_size() and __counted_by()
Link: https://lore.kernel.org/r/7e9e958841f049026c0023b309cc9deecf0ab61d.1710670958.git.u.kleine-koenig@pengutronix.de


Signed-off-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
parent e9cc807f

drivers/pwm/core.c

+10 −17
Original line number Diff line number Diff line
@@ -987,7 +987,7 @@ static void pwmchip_sysfs_unexport(struct pwm_chip *chip) 


static void *pwmchip_priv(struct pwm_chip *chip)

{

	return (void *)chip + ALIGN(sizeof(*chip), PWMCHIP_ALIGN);

	return (void *)chip + ALIGN(struct_size(chip, pwms, chip->npwm), PWMCHIP_ALIGN);

}



/* This is the counterpart to pwmchip_alloc() */
@@ -1001,8 +1001,10 @@ struct pwm_chip *pwmchip_alloc(struct device *parent, unsigned int npwm, size_t 
{

	struct pwm_chip *chip;

	size_t alloc_size;

	unsigned int i;



	alloc_size = size_add(ALIGN(sizeof(*chip), PWMCHIP_ALIGN), sizeof_priv);

	alloc_size = size_add(ALIGN(struct_size(chip, pwms, npwm), PWMCHIP_ALIGN),

			      sizeof_priv);



	chip = kzalloc(alloc_size, GFP_KERNEL);

	if (!chip)
@@ -1014,6 +1016,12 @@ struct pwm_chip *pwmchip_alloc(struct device *parent, unsigned int npwm, size_t 


	pwmchip_set_drvdata(chip, pwmchip_priv(chip));



	for (i = 0; i < chip->npwm; i++) {

		struct pwm_device *pwm = &chip->pwms[i];

		pwm->chip = chip;

		pwm->hwpwm = i;

	}



	return chip;

}

EXPORT_SYMBOL_GPL(pwmchip_alloc);
@@ -1085,7 +1093,6 @@ static bool pwm_ops_check(const struct pwm_chip *chip) 
 */

int __pwmchip_add(struct pwm_chip *chip, struct module *owner)

{

	unsigned int i;

	int ret;



	if (!chip || !pwmchip_parent(chip) || !chip->ops || !chip->npwm)
@@ -1105,28 +1112,16 @@ int __pwmchip_add(struct pwm_chip *chip, struct module *owner) 


	chip->owner = owner;



	chip->pwms = kcalloc(chip->npwm, sizeof(*chip->pwms), GFP_KERNEL);

	if (!chip->pwms)

		return -ENOMEM;



	mutex_lock(&pwm_lock);



	ret = idr_alloc(&pwm_chips, chip, 0, 0, GFP_KERNEL);

	if (ret < 0) {

		mutex_unlock(&pwm_lock);

		kfree(chip->pwms);

		return ret;

	}



	chip->id = ret;



	for (i = 0; i < chip->npwm; i++) {

		struct pwm_device *pwm = &chip->pwms[i];



		pwm->chip = chip;

		pwm->hwpwm = i;

	}



	mutex_unlock(&pwm_lock);



	if (IS_ENABLED(CONFIG_OF))
@@ -1156,8 +1151,6 @@ void pwmchip_remove(struct pwm_chip *chip) 
	idr_remove(&pwm_chips, chip->id);



	mutex_unlock(&pwm_lock);



	kfree(chip->pwms);

}

EXPORT_SYMBOL_GPL(pwmchip_remove);

include/linux/pwm.h

+1 −1
Original line number Diff line number Diff line
@@ -290,7 +290,7 @@ struct pwm_chip { 
	/* only used internally by the PWM framework */

	bool uses_pwmchip_alloc;

	void *driver_data;

	struct pwm_device *pwms;

	struct pwm_device pwms[] __counted_by(npwm);

};



static inline struct device *pwmchip_parent(const struct pwm_chip *chip)