drivers: phy: Add support for optional phys

Add devm_phy_optional_get and phy_optional_get, which should be used
when the phy is optional. They does not return an error when the phy
does not exist, rather they returns NULL, which is considered as a valid
phy, but results in NOPs when used with the consumer API.

Signed-off-by: Andrew Lunn <[email protected]>
Tested-by: Gregory CLEMENT <[email protected]>
Acked-by: Kishon Vijay Abraham I <[email protected]>
Signed-off-by: Jason Cooper <[email protected]>

drivers/phy/phy-core.c

@@ -425,6 +425,27 @@ struct phy *phy_get(struct device *dev, const char *string)
 }
 EXPORT_SYMBOL_GPL(phy_get);
 
+/**
+ * phy_optional_get() - lookup and obtain a reference to an optional phy.
+ * @dev: device that requests this phy
+ * @string: the phy name as given in the dt data or the name of the controller
+ * port for non-dt case
+ *
+ * Returns the phy driver, after getting a refcount to it; or
+ * NULL if there is no such phy.  The caller is responsible for
+ * calling phy_put() to release that count.
+ */
+struct phy *phy_optional_get(struct device *dev, const char *string)
+{
+	struct phy *phy = phy_get(dev, string);
+
+	if (PTR_ERR(phy) == -ENODEV)
+		phy = NULL;
+
+	return phy;
+}
+EXPORT_SYMBOL_GPL(phy_optional_get);
+
 /**
  * devm_phy_get() - lookup and obtain a reference to a phy.
  * @dev: device that requests this phy
@@ -455,6 +476,30 @@ struct phy *devm_phy_get(struct device *dev, const char *string)
 }
 EXPORT_SYMBOL_GPL(devm_phy_get);
 
+/**
+ * devm_phy_optional_get() - lookup and obtain a reference to an optional phy.
+ * @dev: device that requests this phy
+ * @string: the phy name as given in the dt data or phy device name
+ * for non-dt case
+ *
+ * Gets the phy using 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_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_phy_optional_get(struct device *dev, const char *string)
+{
+	struct phy *phy = devm_phy_get(dev, string);
+
+	if (PTR_ERR(phy) == -ENODEV)
+		phy = NULL;
+
+	return phy;
+}
+EXPORT_SYMBOL_GPL(devm_phy_optional_get);
+
 /**
  * phy_create() - create a new phy
  * @dev: device that is creating the new phy