regulator: Add ena_gpio_initialized to regulator_config

Most drivers do not set the ena_gpio field of struct regulator_config
before passing it to the regulator core. This is fine as long as the
gpio identifier that is passed is a positive integer. But the gpio
identifier 0 is also valid. So we are not able to decide wether we got a
real gpio identifier or not based on a 0 in ena_gpio.

To be able to decide if it is a valid gpio that got passed, this patch
adds a ena_gpio_initialized field that should be set if was initialized
with a correct value, either a gpio >= 0 or a negative error number. The
core then checks if ena_gpio or ena_gpio_initialized before handling it
as a gpio. This way we maintain backwards compatibility and fix the
behaviour for gpio number 0.
Signed-off-by: NMarkus Pargmann <mpa@pengutronix.de>
Signed-off-by: NMark Brown <broonie@kernel.org>

drivers/regulator/core.c

@@ -3650,7 +3650,8 @@ regulator_register(const struct regulator_desc *regulator_desc,
 
 	dev_set_drvdata(&rdev->dev, rdev);
 
-	if (config->ena_gpio && gpio_is_valid(config->ena_gpio)) {
+	if ((config->ena_gpio || config->ena_gpio_initialized) &&
+	    gpio_is_valid(config->ena_gpio)) {
 		ret = regulator_ena_gpio_request(rdev, config);
 		if (ret != 0) {
 			rdev_err(rdev, "Failed to request enable GPIO%d: %d\n",

include/linux/regulator/driver.h

@@ -301,6 +301,9 @@ struct regulator_desc {
  *           NULL).
  * @regmap: regmap to use for core regmap helpers if dev_get_regulator() is
  *          insufficient.
+ * @ena_gpio_initialized: GPIO controlling regulator enable was properly
+ *                        initialized, meaning that >= 0 is a valid gpio
+ *                        identifier and < 0 is a non existent gpio.
  * @ena_gpio: GPIO controlling regulator enable.
  * @ena_gpio_invert: Sense for GPIO enable control.
  * @ena_gpio_flags: Flags to use when calling gpio_request_one()
@@ -312,6 +315,7 @@ struct regulator_config {
 	struct device_node *of_node;
 	struct regmap *regmap;
 
+	bool ena_gpio_initialized;
 	int ena_gpio;
 	unsigned int ena_gpio_invert:1;
 	unsigned int ena_gpio_flags;