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>

1 files changed, 15 insertions, 8 deletions

diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index eae215ef1b2c..08fad7c6a471 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -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);