phy: Add devm_of_phy_optional_get() helper

Add an optional variant of devm_of_phy_get() that also takes care of
printing real errors, so drivers no longer have to open-code this
operation.

Signed-off-by: Geert Uytterhoeven <[e-mail]>
Link: https://lore.kernel.org/r/4cd00[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

Documentation/driver-api/phy/phy.rst

···
 					  const char *string);
 	struct phy *devm_of_phy_get(struct device *dev, struct device_node *np,
 				    const char *con_id);
+	struct phy *devm_of_phy_optional_get(struct device *dev,
+					     struct device_node *np,
+					     const char *con_id);
 	struct phy *devm_of_phy_get_by_index(struct device *dev,
 					     struct device_node *np,
 					     int index);
···
 devm_phy_get associates the device with the PHY using devres on
 successful PHY get. On driver detach, release function is invoked on
 the devres data and devres data is freed.
-devm_phy_optional_get should be used when the phy is optional. This
-function will never return -ENODEV, but instead returns NULL when
+The _optional_get variants should be used when the phy is optional. These
+functions will never return -ENODEV, but instead return NULL when
 the phy cannot be found.
 Some generic drivers, such as ehci, may use multiple phys. In this case,
 devm_of_phy_get or devm_of_phy_get_by_index can be used to get a phy

drivers/phy/phy-core.c

···
 EXPORT_SYMBOL_GPL(devm_of_phy_get);
 
 /**
+ * devm_of_phy_optional_get() - lookup and obtain a reference to an optional
+ * phy.
+ * @dev: device that requests this phy
+ * @np: node containing the phy
+ * @con_id: name of the phy from device's point of view
+ *
+ * Gets the phy using of_phy_get(), and associates a device with it using
+ * devres. On driver detach, release function is invoked on the devres data,
+ * then, devres data is freed.  This differs to devm_of_phy_get() in
+ * that if the phy does not exist, it is not considered an error and
+ * -ENODEV will not be returned. Instead the NULL phy is returned,
+ * which can be passed to all other phy consumer calls.
+ */
+struct phy *devm_of_phy_optional_get(struct device *dev, struct device_node *np,
+				     const char *con_id)
+{
+	struct phy *phy = devm_of_phy_get(dev, np, con_id);
+
+	if (PTR_ERR(phy) == -ENODEV)
+		phy = NULL;
+
+	if (IS_ERR(phy))
+		dev_err_probe(dev, PTR_ERR(phy), "failed to get PHY %pOF:%s",
+			      np, con_id);
+
+	return phy;
+}
+EXPORT_SYMBOL_GPL(devm_of_phy_optional_get);
+
+/**
  * devm_of_phy_get_by_index() - lookup and obtain a reference to a phy by index.
  * @dev: device that requests this phy
  * @np: node containing the phy

include/linux/phy/phy.h

···
 struct phy *devm_phy_optional_get(struct device *dev, const char *string);
 struct phy *devm_of_phy_get(struct device *dev, struct device_node *np,
 			    const char *con_id);
+struct phy *devm_of_phy_optional_get(struct device *dev, struct device_node *np,
+				     const char *con_id);
 struct phy *devm_of_phy_get_by_index(struct device *dev, struct device_node *np,
 				     int index);
 void of_phy_put(struct phy *phy);
···
 					  const char *con_id)
 {
 	return ERR_PTR(-ENOSYS);
+}
+
+static inline struct phy *devm_of_phy_optional_get(struct device *dev,
+						   struct device_node *np,
+						   const char *con_id)
+{
+	return NULL;
 }
 
 static inline struct phy *devm_of_phy_get_by_index(struct device *dev,