hwmon: (pmbus) Add pmbus_set_update() function to set update flag

For the STPDDC60 chip, the vout alarm-limits are represented as an offset
relative to the commanded output voltage. This means that the limits are
dynamic and must not be cached by the pmbus driver. This patch adds a
pmbus_set_sensor() function to pmbus_core to be able to set the update flag
on selected sensors after auto-detection of limit attributes.
Signed-off-by: Erik Rosen <erik.rosen@metormote.com>
Link: https://lore.kernel.org/r/20210218115249.28513-2-erik.rosen@metormote.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/pmbus/pmbus.h

@@ -475,6 +475,7 @@ extern const struct regulator_ops pmbus_regulator_ops;
 /* Function declarations */
 
 void pmbus_clear_cache(struct i2c_client *client);
+void pmbus_set_update(struct i2c_client *client, u8 reg, bool update);
 int pmbus_set_page(struct i2c_client *client, int page, int phase);
 int pmbus_read_word_data(struct i2c_client *client, int page, int phase,
 			 u8 reg);

drivers/hwmon/pmbus/pmbus_core.c

@@ -141,6 +141,17 @@ void pmbus_clear_cache(struct i2c_client *client)
 }
 EXPORT_SYMBOL_GPL(pmbus_clear_cache);
 
+void pmbus_set_update(struct i2c_client *client, u8 reg, bool update)
+{
+	struct pmbus_data *data = i2c_get_clientdata(client);
+	struct pmbus_sensor *sensor;
+
+	for (sensor = data->sensors; sensor; sensor = sensor->next)
+		if (sensor->reg == reg)
+			sensor->update = update;
+}
+EXPORT_SYMBOL_GPL(pmbus_set_update);
+
 int pmbus_set_page(struct i2c_client *client, int page, int phase)
 {
 	struct pmbus_data *data = i2c_get_clientdata(client);