regulator: provide a helper for registering a fixed regulator

Some devices require a regulator to work, but boards may not have
a software controllable regulator for this device. Provide a helper
function to make it simpler for these boards to register a fixed
regulator as a dummy regulator.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/regulator/Makefile

@@ -3,7 +3,7 @@
 #
 
 
-obj-$(CONFIG_REGULATOR) += core.o dummy.o
+obj-$(CONFIG_REGULATOR) += core.o dummy.o fixed-helper.o
 obj-$(CONFIG_OF) += of_regulator.o
 obj-$(CONFIG_REGULATOR_FIXED_VOLTAGE) += fixed.o
 obj-$(CONFIG_REGULATOR_VIRTUAL_CONSUMER) += virtual.o

drivers/regulator/fixed-helper.c

+#include <linux/slab.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/machine.h>
+#include <linux/regulator/fixed.h>
+
+struct fixed_regulator_data {
+	struct fixed_voltage_config cfg;
+	struct regulator_init_data init_data;
+	struct platform_device pdev;
+};
+
+static void regulator_fixed_release(struct device *dev)
+{
+	struct fixed_regulator_data *data = container_of(dev,
+			struct fixed_regulator_data, pdev.dev);
+	kfree(data);
+}
+
+/**
+ * regulator_register_fixed - register a no-op fixed regulator
+ * @name: supply name
+ * @id: platform device id
+ * @supplies: consumers for this regulator
+ * @num_supplies: number of consumers
+ */
+struct platform_device *regulator_register_fixed(int id,
+		struct regulator_consumer_supply *supplies, int num_supplies)
+{
+	struct fixed_regulator_data *data;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return NULL;
+
+	data->cfg.supply_name = "dummy";
+	data->cfg.microvolts = 0;
+	data->cfg.gpio = -EINVAL;
+	data->cfg.enabled_at_boot = 1;
+	data->cfg.init_data = &data->init_data;
+
+	data->init_data.constraints.always_on = 1;
+	data->init_data.consumer_supplies = supplies;
+	data->init_data.num_consumer_supplies = num_supplies;
+
+	data->pdev.name = "reg-fixed-voltage";
+	data->pdev.id = id;
+	data->pdev.dev.platform_data = &data->cfg;
+	data->pdev.dev.release = regulator_fixed_release;
+
+	platform_device_register(&data->pdev);
+
+	return &data->pdev;
+}

include/linux/regulator/fixed.h

@@ -48,4 +48,17 @@ struct fixed_voltage_config {
 	struct regulator_init_data *init_data;
 };
 
+struct regulator_consumer_supply;
+
+#if IS_ENABLED(CONFIG_REGULATOR)
+struct platform_device *regulator_register_fixed(int id,
+		struct regulator_consumer_supply *supplies, int num_supplies);
+#else
+static inline struct platform_device *regulator_register_fixed(int id,
+		struct regulator_consumer_supply *supplies, int num_supplies)
+{
+	return NULL;
+}
+#endif
+
 #endif