[PATCH RFC 1/7] regulator: devres: add APIs for reference supplies

[David Lechner]

A common use case for regulators is to supply a reference voltage to an
analog input or output device. This adds two new devres APIs to get,
enable, and get the voltage in a single call. This allows eliminating
boilerplate code in drivers that use reference supplies in this way.

devm_regulator_get_enable_get_voltage() is intended for cases where the
supply is required to provide an external reference voltage.

devm_regulator_get_optional_enable_get_voltage() is intended for cases
where the supply is optional and device typically uses an internal
reference voltage if the supply is not available.

Signed-off-by: David Lechner <dlechner@xxxxxxxxxxxx>
---
 Documentation/driver-api/driver-model/devres.rst |  2 +
 drivers/regulator/devres.c                       | 83 ++++++++++++++++++++++++
 include/linux/regulator/consumer.h               | 14 ++++
 3 files changed, 99 insertions(+)

diff --git a/Documentation/driver-api/driver-model/devres.rst b/Documentation/driver-api/driver-model/devres.rst
index 7be8b8dd5f00..fd954d09e13c 100644
--- a/Documentation/driver-api/driver-model/devres.rst
+++ b/Documentation/driver-api/driver-model/devres.rst
@@ -433,9 +433,11 @@ REGULATOR
   devm_regulator_bulk_put()
   devm_regulator_get()
   devm_regulator_get_enable()
+  devm_regulator_get_enable_get_voltage()
   devm_regulator_get_enable_optional()
   devm_regulator_get_exclusive()
   devm_regulator_get_optional()
+  devm_regulator_get_optional_enable_get_voltage()
   devm_regulator_irq_helper()
   devm_regulator_put()
   devm_regulator_register()
diff --git a/drivers/regulator/devres.c b/drivers/regulator/devres.c
index 90bb0d178885..e240926defc5 100644
--- a/drivers/regulator/devres.c
+++ b/drivers/regulator/devres.c
@@ -145,6 +145,89 @@ struct regulator *devm_regulator_get_optional(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(devm_regulator_get_optional);
 
+static int _devm_regulator_get_enable_get_voltage(struct device *dev,
+						  const char *id,
+						  bool silent_enodev)
+{
+	struct regulator *r;
+	int ret;
+
+	/*
+	 * Since we need a real voltage, we use devm_regulator_get_optional()
+	 * here to avoid getting a dummy regulator if the supply is not present.
+	 */
+	r = devm_regulator_get_optional(dev, id);
+	if (silent_enodev && PTR_ERR(r) == -ENODEV)
+		return -ENODEV;
+	if (IS_ERR(r))
+		return dev_err_probe(dev, PTR_ERR(r),
+				     "failed to get regulator '%s'\n", id);
+
+	ret = regulator_enable(r);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "failed to enable regulator '%s'\n", id);
+
+	ret = devm_add_action_or_reset(dev, regulator_action_disable, r);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "failed to add disable action for regulator '%s'\n",
+				     id);
+
+	ret = regulator_get_voltage(r);
+	if (ret < 0)
+		return dev_err_probe(dev, ret,
+				     "failed to get voltage for regulator '%s'\n",
+				     id);
+
+	return ret;
+}
+
+/**
+ * devm_regulator_get_enable_get_voltage - Resource managed regulator get and
+ *                                         enable that returns the voltage
+ * @dev: device to supply
+ * @id:  supply name or regulator ID.
+ *
+ * Get and enable regulator for duration of the device life-time.
+ * regulator_disable() and regulator_put() are automatically called on driver
+ * detach. See regulator_get_optional(), regulator_enable(), and
+ * regulator_get_voltage() for more information.
+ *
+ * This is a convenience function for supplies that provide a reference voltage
+ * where the consumer driver just needs to know the voltage and keep the
+ * regulator enabled. Also, as a convenience, this prints error messages on
+ * failure.
+ *
+ * Returns: voltage in microvolts on success, or an error code on failure.
+ */
+int devm_regulator_get_enable_get_voltage(struct device *dev, const char *id)
+{
+	return _devm_regulator_get_enable_get_voltage(dev, id, false);
+}
+EXPORT_SYMBOL_GPL(devm_regulator_get_enable_get_voltage);
+
+/**
+ * devm_regulator_get_optional_enable_get_voltage - Resource managed regulator
+ *                                                  get and enable that returns
+ *                                                  the voltage
+ * @dev: device to supply
+ * @id:  supply name or regulator ID.
+ *
+ * This function is identical to devm_regulator_get_enable_get_voltage() except
+ * that it does not print an error message in the case of -ENODEV. Callers are
+ * expected to handle -ENODEV as a special case instead of passing it on as an
+ * error.
+ *
+ * Returns: voltage in microvolts on success, or an error code on failure.
+ */
+int devm_regulator_get_optional_enable_get_voltage(struct device *dev,
+						   const char *id)
+{
+	return _devm_regulator_get_enable_get_voltage(dev, id, true);
+}
+EXPORT_SYMBOL_GPL(devm_regulator_get_optional_enable_get_voltage);
+
 static int devm_regulator_match(struct device *dev, void *res, void *data)
 {
 	struct regulator **r = res;
diff --git a/include/linux/regulator/consumer.h b/include/linux/regulator/consumer.h
index 4660582a3302..35596db521a0 100644
--- a/include/linux/regulator/consumer.h
+++ b/include/linux/regulator/consumer.h
@@ -164,6 +164,8 @@ struct regulator *__must_check devm_regulator_get_optional(struct device *dev,
 							   const char *id);
 int devm_regulator_get_enable(struct device *dev, const char *id);
 int devm_regulator_get_enable_optional(struct device *dev, const char *id);
+int devm_regulator_get_enable_get_voltage(struct device *dev, const char *id);
+int devm_regulator_get_optional_enable_get_voltage(struct device *dev, const char *id);
 void regulator_put(struct regulator *regulator);
 void devm_regulator_put(struct regulator *regulator);
 
@@ -329,6 +331,18 @@ static inline int devm_regulator_get_enable_optional(struct device *dev,
 	return -ENODEV;
 }
 
+static inline int devm_regulator_get_enable_get_voltage(struct device *dev,
+							const char *id)
+{
+	return -ENODEV;
+}
+
+static inline int devm_regulator_get_optional_enable_get_voltage(struct device *dev,
+								 const char *id)
+{
+	return -ENODEV;
+}
+
 static inline struct regulator *__must_check
 regulator_get_optional(struct device *dev, const char *id)
 {

-- 
2.43.2