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

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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: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
This commit is contained in:
Uwe Kleine-König 2024-03-17 11:40:35 +01:00
parent e9cc807f87
commit ee37bf5074
2 changed files with 11 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
drivers/pwm/core.c
View File

@ -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);

2
include/linux/pwm.h
View File

@ -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)