ds2760_battery: add rated_capacity module parameter

For systems where the ds2760 is soldered directly on the PCB, the 'rated
capacity' register is not set to anything useful.

In order to allow users to bootstrap this value, introduce a new module
parameter 'rated_capacity' and use it to write the internal EEPROM in
case the value differes from what's been given.

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Cc: Szabolcs Gyurko <szabolcs.gyurko@tlt.hu>
Acked-by: Matt Reimer <mreimer@vpop.net>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>
diff --git a/drivers/power/ds2760_battery.c b/drivers/power/ds2760_battery.c
index f439071..ed0ea5e 100644
--- a/drivers/power/ds2760_battery.c
+++ b/drivers/power/ds2760_battery.c
@@ -66,6 +66,10 @@
 module_param(pmod_enabled, bool, 0644);
 MODULE_PARM_DESC(pmod_enabled, "PMOD enable bit");
 
+static unsigned int rated_capacity;
+module_param(rated_capacity, uint, 0644);
+MODULE_PARM_DESC(rated_capacity, "rated battery capacity, 10*mAh or index");
+
 /* Some batteries have their rated capacity stored a N * 10 mAh, while
  * others use an index into this table. */
 static int rated_capacities[] = {
@@ -274,6 +278,17 @@
 	w1_ds2760_recall_eeprom(di->w1_dev, DS2760_EEPROM_BLOCK1);
 }
 
+static void ds2760_battery_write_rated_capacity(struct ds2760_device_info *di,
+						unsigned char rated_capacity)
+{
+	if (rated_capacity == di->raw[DS2760_RATED_CAPACITY])
+		return;
+
+	w1_ds2760_write(di->w1_dev, &rated_capacity, DS2760_RATED_CAPACITY, 1);
+	w1_ds2760_store_eeprom(di->w1_dev, DS2760_EEPROM_BLOCK1);
+	w1_ds2760_recall_eeprom(di->w1_dev, DS2760_EEPROM_BLOCK1);
+}
+
 static void ds2760_battery_work(struct work_struct *work)
 {
 	struct ds2760_device_info *di = container_of(work,
@@ -399,6 +414,10 @@
 
 	ds2760_battery_write_status(di, status);
 
+	/* set rated capacity from module param */
+	if (rated_capacity)
+		ds2760_battery_write_rated_capacity(di, rated_capacity);
+
 	retval = power_supply_register(&pdev->dev, &di->bat);
 	if (retval) {
 		dev_err(di->dev, "failed to register battery\n");