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 life 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 <[email protected]> # for struct_size() and __counted_by() Signed-off-by: Uwe Kleine-König <[email protected]> --- drivers/pwm/core.c | 27 ++++++++++----------------- include/linux/pwm.h | 2 +- 2 files changed, 11 insertions(+), 18 deletions(-) diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c index 80acae5fed11..e5024dff56b3 100644 --- a/drivers/pwm/core.c +++ b/drivers/pwm/core.c @@ -456,15 +456,16 @@ EXPORT_SYMBOL_GPL(of_pwm_single_xlate); static void *pwmchip_priv(struct pwm_chip *chip) { - return (void *)chip + sizeof(*chip); + return (void *)chip + struct_size(chip, pwms, chip->npwm); } struct pwm_chip *devm_pwmchip_alloc(struct device *parent, unsigned int npwm, size_t sizeof_priv) { struct pwm_chip *chip; size_t alloc_size; + unsigned int i; - alloc_size = size_add(sizeof(*chip), sizeof_priv); + alloc_size = size_add(struct_size(chip, pwms, npwm), sizeof_priv); chip = devm_kzalloc(parent, alloc_size, GFP_KERNEL); if (!chip) @@ -476,6 +477,13 @@ struct pwm_chip *devm_pwmchip_alloc(struct device *parent, unsigned int npwm, si 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(devm_pwmchip_alloc); @@ -523,7 +531,6 @@ 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 || !chip->dev || !chip->ops || !chip->npwm) @@ -543,28 +550,16 @@ 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)) @@ -594,8 +589,6 @@ 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); diff --git a/include/linux/pwm.h b/include/linux/pwm.h index 1620a1eef165..d505400f8573 100644 --- a/include/linux/pwm.h +++ b/include/linux/pwm.h @@ -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(struct pwm_chip *chip) -- 2.43.0
