power: supply: add helpers for charge_behaviour sysfs

These helper functions can be used by drivers to implement their own
sysfs-attributes.
This is useful for ACPI-drivers extending the default ACPI-battery with
their own charge_behaviour attributes.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20211123232704.25394-3-linux@weissschuh.netSigned-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/power/supply/power_supply_sysfs.c

@@ -133,6 +133,12 @@ static const char * const POWER_SUPPLY_SCOPE_TEXT[] = {
 	[POWER_SUPPLY_SCOPE_DEVICE]	= "Device",
 };
 
+static const char * const POWER_SUPPLY_CHARGE_BEHAVIOUR_TEXT[] = {
+	[POWER_SUPPLY_CHARGE_BEHAVIOUR_AUTO]		= "auto",
+	[POWER_SUPPLY_CHARGE_BEHAVIOUR_INHIBIT_CHARGE]	= "inhibit-charge",
+	[POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE]	= "force-discharge",
+};
+
 static struct power_supply_attr power_supply_attrs[] = {
 	/* Properties of type `int' */
 	POWER_SUPPLY_ENUM_ATTR(STATUS),
@@ -484,3 +490,52 @@ int power_supply_uevent(struct device *dev, struct kobj_uevent_env *env)
 
 	return ret;
 }
+
+ssize_t power_supply_charge_behaviour_show(struct device *dev,
+					   unsigned int available_behaviours,
+					   enum power_supply_charge_behaviour current_behaviour,
+					   char *buf)
+{
+	bool match = false, available, active;
+	ssize_t count = 0;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(POWER_SUPPLY_CHARGE_BEHAVIOUR_TEXT); i++) {
+		available = available_behaviours & BIT(i);
+		active = i == current_behaviour;
+
+		if (available && active) {
+			count += sysfs_emit_at(buf, count, "[%s] ",
+					       POWER_SUPPLY_CHARGE_BEHAVIOUR_TEXT[i]);
+			match = true;
+		} else if (available) {
+			count += sysfs_emit_at(buf, count, "%s ",
+					       POWER_SUPPLY_CHARGE_BEHAVIOUR_TEXT[i]);
+		}
+	}
+
+	if (!match) {
+		dev_warn(dev, "driver reporting unsupported charge behaviour\n");
+		return -EINVAL;
+	}
+
+	if (count)
+		buf[count - 1] = '\n';
+
+	return count;
+}
+EXPORT_SYMBOL_GPL(power_supply_charge_behaviour_show);
+
+int power_supply_charge_behaviour_parse(unsigned int available_behaviours, const char *buf)
+{
+	int i = sysfs_match_string(POWER_SUPPLY_CHARGE_BEHAVIOUR_TEXT, buf);
+
+	if (i < 0)
+		return i;
+
+	if (available_behaviours & BIT(i))
+		return i;
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(power_supply_charge_behaviour_parse);

include/linux/power_supply.h

@@ -546,4 +546,13 @@ static inline
 void power_supply_remove_hwmon_sysfs(struct power_supply *psy) {}
 #endif
 
+#ifdef CONFIG_SYSFS
+ssize_t power_supply_charge_behaviour_show(struct device *dev,
+					   unsigned int available_behaviours,
+					   enum power_supply_charge_behaviour behaviour,
+					   char *buf);
+
+int power_supply_charge_behaviour_parse(unsigned int available_behaviours, const char *buf);
+#endif
+
 #endif /* __LINUX_POWER_SUPPLY_H__ */