regulator: core: Track dangling GPIO descriptors

If a GPIO descriptor is passed to the regulator_register()
function inside the config->ena_gpiod callers must be
sure that once they call this API the regulator core
owns that descriptor and will make sure to issue
gpiod_put() on it, no matter whether the call is
successful or not.

For device tree regulators, the regulator core will
automatically set up regulator init data from the device
tree when registering a regulator by calling
regulator_of_get_init_data() which in turn calls down to
the regulator driver's .of_parse_cb() callback.
This callback (in drivers such as for max77686) may also
choose to fill in the config->ena_gpiod field with a GPIO
descriptor.

Harden the errorpath of regulator_register() to
properly gpiod_put() any passed in cfg->ena_gpiod
or any gpiod coming from the device tree on any type
of error.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/core.c

@@ -4868,21 +4868,33 @@ regulator_register(const struct regulator_desc *regulator_desc,
 	struct regulator_config *config = NULL;
 	static atomic_t regulator_no = ATOMIC_INIT(-1);
 	struct regulator_dev *rdev;
+	bool dangling_cfg_gpiod = false;
+	bool dangling_of_gpiod = false;
 	struct device *dev;
 	int ret, i;
 
-	if (regulator_desc == NULL || cfg == NULL)
+	if (cfg == NULL)
 		return ERR_PTR(-EINVAL);
+	if (cfg->ena_gpiod)
+		dangling_cfg_gpiod = true;
+	if (regulator_desc == NULL) {
+		ret = -EINVAL;
+		goto rinse;
+	}
 
 	dev = cfg->dev;
 	WARN_ON(!dev);
 
-	if (regulator_desc->name == NULL || regulator_desc->ops == NULL)
-		return ERR_PTR(-EINVAL);
+	if (regulator_desc->name == NULL || regulator_desc->ops == NULL) {
+		ret = -EINVAL;
+		goto rinse;
+	}
 
 	if (regulator_desc->type != REGULATOR_VOLTAGE &&
-	    regulator_desc->type != REGULATOR_CURRENT)
-		return ERR_PTR(-EINVAL);
+	    regulator_desc->type != REGULATOR_CURRENT) {
+		ret = -EINVAL;
+		goto rinse;
+	}
 
 	/* Only one of each should be implemented */
 	WARN_ON(regulator_desc->ops->get_voltage &&
@@ -4893,16 +4905,20 @@ regulator_register(const struct regulator_desc *regulator_desc,
 	/* If we're using selectors we must implement list_voltage. */
 	if (regulator_desc->ops->get_voltage_sel &&
 	    !regulator_desc->ops->list_voltage) {
-		return ERR_PTR(-EINVAL);
+		ret = -EINVAL;
+		goto rinse;
 	}
 	if (regulator_desc->ops->set_voltage_sel &&
 	    !regulator_desc->ops->list_voltage) {
-		return ERR_PTR(-EINVAL);
+		ret = -EINVAL;
+		goto rinse;
 	}
 
 	rdev = kzalloc(sizeof(struct regulator_dev), GFP_KERNEL);
-	if (rdev == NULL)
-		return ERR_PTR(-ENOMEM);
+	if (rdev == NULL) {
+		ret = -ENOMEM;
+		goto rinse;
+	}
 
 	/*
 	 * Duplicate the config so the driver could override it after
@@ -4911,11 +4927,22 @@ regulator_register(const struct regulator_desc *regulator_desc,
 	config = kmemdup(cfg, sizeof(*cfg), GFP_KERNEL);
 	if (config == NULL) {
 		kfree(rdev);
-		return ERR_PTR(-ENOMEM);
+		ret = -ENOMEM;
+		goto rinse;
 	}
 
 	init_data = regulator_of_get_init_data(dev, regulator_desc, config,
 					       &rdev->dev.of_node);
+	/*
+	 * We need to keep track of any GPIO descriptor coming from the
+	 * device tree until we have handled it over to the core. If the
+	 * config that was passed in to this function DOES NOT contain
+	 * a descriptor, and the config after this call DOES contain
+	 * a descriptor, we definately got one from parsing the device
+	 * tree.
+	 */
+	if (!cfg->ena_gpiod && config->ena_gpiod)
+		dangling_of_gpiod = true;
 	if (!init_data) {
 		init_data = config->init_data;
 		rdev->dev.of_node = of_node_get(config->of_node);
@@ -4954,6 +4981,9 @@ regulator_register(const struct regulator_desc *regulator_desc,
 				 config->ena_gpio, ret);
 			goto clean;
 		}
+		/* The regulator core took over the GPIO descriptor */
+		dangling_cfg_gpiod = false;
+		dangling_of_gpiod = false;
 	}
 
 	/* register with sysfs */
@@ -5039,8 +5069,13 @@ regulator_register(const struct regulator_desc *regulator_desc,
 	regulator_ena_gpio_free(rdev);
 	mutex_unlock(&regulator_list_mutex);
 clean:
+	if (dangling_of_gpiod)
+		gpiod_put(config->ena_gpiod);
 	kfree(rdev);
 	kfree(config);
+rinse:
+	if (dangling_cfg_gpiod)
+		gpiod_put(cfg->ena_gpiod);
 	return ERR_PTR(ret);
 }
 EXPORT_SYMBOL_GPL(regulator_register);