power: suppy: ucs1002: disable power when max current is 0

For some devices userspace needs the ability to completely cut the power
to the USB devices connected to the charge controller. An easy way to
achieve this is by allowing 0 as a valid max current and forcibly disable
the output in that case, as well as enable it again if the regulator is
in use and a non-0 max current is set.

Signed-off-by: Lucas Stach <[e-mail]>
Tested-by: Chris Healy <[e-mail]>
Signed-off-by: Sebastian Reichel <[e-mail]>

drivers/power/supply/ucs1002_power.c

···
 	struct i2c_client *client;
 	struct regmap *regmap;
 	struct regulator_desc *regulator_descriptor;
+	struct regulator_dev *rdev;
 	bool present;
+	bool output_disable;
 };
 
 static enum power_supply_property ucs1002_props[] = {
···
 	unsigned int reg;
 	int ret;
 
+	if (info->output_disable) {
+		val->intval = 0;
+		return 0;
+	}
+
 	ret = regmap_read(info->regmap, UCS1002_REG_ILIMIT, &reg);
 	if (ret)
 		return ret;
···
 {
 	unsigned int reg;
 	int ret, idx;
+
+	if (val == 0) {
+		info->output_disable = true;
+		regulator_disable_regmap(info->rdev);
+		return 0;
+	}
 
 	for (idx = 0; idx < ARRAY_SIZE(ucs1002_current_limit_uA); idx++) {
 		if (val == ucs1002_current_limit_uA[idx])
···
 
 	if (reg != idx)
 		return -EINVAL;
+
+	info->output_disable = false;
+
+	if (info->rdev && info->rdev->use_count &&
+	    !regulator_is_enabled_regmap(info->rdev))
+		regulator_enable_regmap(info->rdev);
 
 	return 0;
 }
···
 	return IRQ_HANDLED;
 }
 
+int ucs1002_regulator_enable(struct regulator_dev *rdev)
+{
+	struct ucs1002_info *info = rdev_get_drvdata(rdev);
+
+	/*
+	 * If the output is disabled due to 0 maximum current, just pretend the
+	 * enable did work. The regulator will be enabled as soon as we get a
+	 * a non-zero maximum current budget.
+	 */
+	if (info->output_disable)
+		return 0;
+
+	return regulator_enable_regmap(rdev);
+}
+
 static const struct regulator_ops ucs1002_regulator_ops = {
 	.is_enabled	= regulator_is_enabled_regmap,
-	.enable		= regulator_enable_regmap,
+	.enable		= ucs1002_regulator_enable,
 	.disable	= regulator_disable_regmap,
 };
 
···
 	};
 	struct regulator_config regulator_config = {};
 	int irq_a_det, irq_alert, ret;
-	struct regulator_dev *rdev;
 	struct ucs1002_info *info;
 	unsigned int regval;
 
···
 	regulator_config.dev = dev;
 	regulator_config.of_node = dev->of_node;
 	regulator_config.regmap = info->regmap;
+	regulator_config.driver_data = info;
 
-	rdev = devm_regulator_register(dev, info->regulator_descriptor,
+	info->rdev = devm_regulator_register(dev, info->regulator_descriptor,
 				       &regulator_config);
-	ret = PTR_ERR_OR_ZERO(rdev);
+	ret = PTR_ERR_OR_ZERO(info->rdev);
 	if (ret) {
 		dev_err(dev, "Failed to register VBUS regulator: %d\n", ret);
 		return ret;