regulator: core: add regulator_get_linear_step()

Add regulator_get_linear_step(), which returns the voltage step size
between VSEL values for linear regulators.  This is intended for use
by regulator consumers which build their own voltage-to-VSEL tables.

Signed-off-by: Paul Walmsley <pwalmsley@nvidia.com>
Reviewed-by: Andrew Chew <achew@nvidia.com>
Cc: Matthew Longnecker <mlongnecker@nvidia.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

drivers/regulator/core.c

@@ -2134,6 +2134,21 @@ int regulator_list_voltage(struct regulator *regulator, unsigned selector)
 }
 EXPORT_SYMBOL_GPL(regulator_list_voltage);
 
+/**
+ * regulator_get_linear_step - return the voltage step size between VSEL values
+ * @regulator: regulator source
+ *
+ * Returns the voltage step size between VSEL values for linear
+ * regulators, or return 0 if the regulator isn't a linear regulator.
+ */
+unsigned int regulator_get_linear_step(struct regulator *regulator)
+{
+	struct regulator_dev *rdev = regulator->rdev;
+
+	return rdev->desc->uV_step;
+}
+EXPORT_SYMBOL_GPL(regulator_get_linear_step);
+
 /**
  * regulator_is_supported_voltage - check if a voltage range can be supported
  *

include/linux/regulator/consumer.h

@@ -165,6 +165,7 @@ int regulator_count_voltages(struct regulator *regulator);
 int regulator_list_voltage(struct regulator *regulator, unsigned selector);
 int regulator_is_supported_voltage(struct regulator *regulator,
 				   int min_uV, int max_uV);
+unsigned int regulator_get_linear_step(struct regulator *regulator);
 int regulator_set_voltage(struct regulator *regulator, int min_uV, int max_uV);
 int regulator_set_voltage_time(struct regulator *regulator,
 			       int old_uV, int new_uV);