[RFC PATCH 2/4] regulator: core: Add regulator_map_voltage_descend() API

[Prabhakar]

From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>

Similarly to regulator_map_voltage_ascend() api add
regulator_map_voltage_descend() api and export it.

Drivers that have descendant voltage list can use this as their
map_voltage() operation.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
---
 drivers/regulator/helpers.c      | 31 +++++++++++++++++++++++++++++++
 include/linux/regulator/driver.h |  2 ++
 2 files changed, 33 insertions(+)

diff --git a/drivers/regulator/helpers.c b/drivers/regulator/helpers.c
index 6e1ace660b8c..ac62d778e3c0 100644
--- a/drivers/regulator/helpers.c
+++ b/drivers/regulator/helpers.c
@@ -368,6 +368,37 @@ int regulator_map_voltage_ascend(struct regulator_dev *rdev,
 }
 EXPORT_SYMBOL_GPL(regulator_map_voltage_ascend);
 
+/**
+ * regulator_map_voltage_descend - map_voltage() for descendant voltage list
+ *
+ * @rdev: Regulator to operate on
+ * @min_uV: Lower bound for voltage
+ * @max_uV: Upper bound for voltage
+ *
+ * Drivers that have descendant voltage list can use this as their
+ * map_voltage() operation.
+ */
+int regulator_map_voltage_descend(struct regulator_dev *rdev,
+				  int min_uV, int max_uV)
+{
+	int i, ret;
+
+	for (i = rdev->desc->n_voltages - 1; i >= 0 ; i--) {
+		ret = rdev->desc->ops->list_voltage(rdev, i);
+		if (ret < 0)
+			continue;
+
+		if (ret > min_uV)
+			break;
+
+		if (ret >= min_uV && ret <= max_uV)
+			return i;
+	}
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(regulator_map_voltage_descend);
+
 /**
  * regulator_map_voltage_linear - map_voltage() for simple linear mappings
  *
diff --git a/include/linux/regulator/driver.h b/include/linux/regulator/driver.h
index f230a472ccd3..6410c57ba85a 100644
--- a/include/linux/regulator/driver.h
+++ b/include/linux/regulator/driver.h
@@ -735,6 +735,8 @@ int regulator_map_voltage_iterate(struct regulator_dev *rdev,
 				  int min_uV, int max_uV);
 int regulator_map_voltage_ascend(struct regulator_dev *rdev,
 				  int min_uV, int max_uV);
+int regulator_map_voltage_descend(struct regulator_dev *rdev,
+				  int min_uV, int max_uV);
 int regulator_get_voltage_sel_pickable_regmap(struct regulator_dev *rdev);
 int regulator_set_voltage_sel_pickable_regmap(struct regulator_dev *rdev,
 						unsigned int sel);
-- 
2.34.1