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pwm: Try to load modules during pwm_get() 

Add a module name string to the pwm_lookup struct and if specified try
to load the module using request_module() if pwmchip_find_by_name() is
unable to find the PWM chip.

This is a last resort to work around drivers that can't - and can't be
made to - deal with deferred probe.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
[thierry.reding@gmail.com: rename new macro, reword commit message]
[thierry.reding@gmail.com: add comment explaining use-case]
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
This commit is contained in:
Hans de Goede 2017-01-22 17:14:08 +01:00 committed by Thierry Reding
parent 69efb3439c
commit b526a31426
2 changed files with 29 additions and 8 deletions
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14
drivers/pwm/core.c
View File

@ -765,6 +765,7 @@ struct pwm_device *pwm_get(struct device *dev, const char *con_id)
unsigned int best = 0;
struct pwm_lookup *p, *chosen = NULL;
unsigned int match;
int err;
/* look up via DT first */
if (IS_ENABLED(CONFIG_OF) && dev && dev->of_node)
@ -825,6 +826,19 @@ struct pwm_device *pwm_get(struct device *dev, const char *con_id)
return ERR_PTR(-ENODEV);
chip = pwmchip_find_by_name(chosen->provider);
/*
* If the lookup entry specifies a module, load the module and retry
* the PWM chip lookup. This can be used to work around driver load
* ordering issues if driver's can't be made to properly support the
* deferred probe mechanism.
*/
if (!chip && chosen->module) {
err = request_module(chosen->module);
if (err == 0)
chip = pwmchip_find_by_name(chosen->provider);
}
if (!chip)
return ERR_PTR(-EPROBE_DEFER);

23
include/linux/pwm.h
View File

@ -603,18 +603,25 @@ struct pwm_lookup {
const char *con_id;
unsigned int period;
enum pwm_polarity polarity;
const char *module; /* optional, may be NULL */
};
#define PWM_LOOKUP(_provider, _index, _dev_id, _con_id, _period, _polarity) \
{ \
.provider = _provider, \
.index = _index, \
.dev_id = _dev_id, \
.con_id = _con_id, \
.period = _period, \
.polarity = _polarity \
#define PWM_LOOKUP_WITH_MODULE(_provider, _index, _dev_id, _con_id, \
_period, _polarity, _module) \
{ \
.provider = _provider, \
.index = _index, \
.dev_id = _dev_id, \
.con_id = _con_id, \
.period = _period, \
.polarity = _polarity, \
.module = _module, \
}
#define PWM_LOOKUP(_provider, _index, _dev_id, _con_id, _period, _polarity) \
PWM_LOOKUP_WITH_MODULE(_provider, _index, _dev_id, _con_id, _period, \
_polarity, NULL)
#if IS_ENABLED(CONFIG_PWM)
void pwm_add_table(struct pwm_lookup *table, size_t num);
void pwm_remove_table(struct pwm_lookup *table, size_t num);