power_supply: Add function to return system-wide power state

Certain drivers benefit from knowing whether the system is on ac or
battery, for instance when determining which backlight registers to
read. This adds a simple call to determine whether there's an online
power supply other than any batteries.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
index ea96ead1d39d..f9348cba6dc1 100644
--- a/include/linux/power_supply.h
+++ b/include/linux/power_supply.h
@@ -165,6 +165,12 @@ struct power_supply_info {
 extern void power_supply_changed(struct power_supply *psy);
 extern int power_supply_am_i_supplied(struct power_supply *psy);
 
+#if defined(CONFIG_POWER_SUPPLY) || defined(CONFIG_POWER_SUPPLY_MODULE)
+extern int power_supply_is_system_supplied(void);
+#else
+static inline int power_supply_is_system_supplied(void) { return -ENOSYS; }
+#endif
+
 extern int power_supply_register(struct device *parent,
                                  struct power_supply *psy);
 extern void power_supply_unregister(struct power_supply *psy);