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>

2 files changed, 31 insertions, 0 deletions

diff --git a/drivers/power/power_supply_core.c b/drivers/power/power_supply_core.c
index cb1ccb472921..f44f5b608f6a 100644
--- a/drivers/power/power_supply_core.c
+++ b/drivers/power/power_supply_core.c
@@ -87,6 +87,30 @@ int power_supply_am_i_supplied(struct power_supply *psy)
         return error;
 }
 
+static int __power_supply_is_system_supplied(struct device *dev, void *data)
+{
+        union power_supply_propval ret = {0,};
+        struct power_supply *psy = dev_get_drvdata(dev);
+
+        if (psy->type != POWER_SUPPLY_TYPE_BATTERY) {
+                if (psy->get_property(psy, POWER_SUPPLY_PROP_ONLINE, &ret))
+                        return 0;
+                if (ret.intval)
+                        return ret.intval;
+        }
+        return 0;
+}
+
+int power_supply_is_system_supplied(void)
+{
+        int error;
+
+        error = class_for_each_device(power_supply_class, NULL, NULL,
+                                      __power_supply_is_system_supplied);
+
+        return error;
+}
+
 int power_supply_register(struct device *parent, struct power_supply *psy)
 {
         int rc = 0;
@@ -148,6 +172,7 @@ static void __exit power_supply_class_exit(void)
 
 EXPORT_SYMBOL_GPL(power_supply_changed);
 EXPORT_SYMBOL_GPL(power_supply_am_i_supplied);
+EXPORT_SYMBOL_GPL(power_supply_is_system_supplied);
 EXPORT_SYMBOL_GPL(power_supply_register);
 EXPORT_SYMBOL_GPL(power_supply_unregister);
 
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);