Add a helper function wrapping internal reserved memory
device_init call and expose it externally.

Use the new helper function within of_reserved_mem_device_init_by_idx().

Signed-off-by: Albert Esteve <aesteve@redhat.com>
---
 drivers/of/of_reserved_mem.c    | 68 ++++++++++++++++++++++++++---------------
 include/linux/of_reserved_mem.h |  8 +++++
 2 files changed, 52 insertions(+), 24 deletions(-)

diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
index 1fd28f8056108..26ca871f7f919 100644
--- a/drivers/of/of_reserved_mem.c
+++ b/drivers/of/of_reserved_mem.c
@@ -605,6 +605,49 @@ struct rmem_assigned_device {
 static LIST_HEAD(of_rmem_assigned_device_list);
 static DEFINE_MUTEX(of_rmem_assigned_device_mutex);
 
+/**
+ * of_reserved_mem_device_init_with_mem() - assign reserved memory region to
+ *					    given device
+ * @dev:	Pointer to the device to configure
+ * @rmem:	Reserved memory region to assign
+ *
+ * This function assigns respective DMA-mapping operations based on the
+ * reserved memory region already provided in @rmem to the @dev device,
+ * without walking DT nodes.
+ *
+ * Returns error code or zero on success.
+ */
+int of_reserved_mem_device_init_with_mem(struct device *dev,
+					 struct reserved_mem *rmem)
+{
+	struct rmem_assigned_device *rd;
+	int ret;
+
+	if (!dev || !rmem || !rmem->ops || !rmem->ops->device_init)
+		return -EINVAL;
+
+	rd = kmalloc_obj(struct rmem_assigned_device);
+	if (!rd)
+		return -ENOMEM;
+
+	ret = rmem->ops->device_init(rmem, dev);
+	if (ret == 0) {
+		rd->dev = dev;
+		rd->rmem = rmem;
+
+		mutex_lock(&of_rmem_assigned_device_mutex);
+		list_add(&rd->list, &of_rmem_assigned_device_list);
+		mutex_unlock(&of_rmem_assigned_device_mutex);
+
+		dev_info(dev, "assigned reserved memory node %s\n", rmem->name);
+	} else {
+		kfree(rd);
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(of_reserved_mem_device_init_with_mem);
+
 /**
  * of_reserved_mem_device_init_by_idx() - assign reserved memory region to
  *					  given device
@@ -623,10 +666,8 @@ static DEFINE_MUTEX(of_rmem_assigned_device_mutex);
 int of_reserved_mem_device_init_by_idx(struct device *dev,
 				       struct device_node *np, int idx)
 {
-	struct rmem_assigned_device *rd;
 	struct device_node *target;
 	struct reserved_mem *rmem;
-	int ret;
 
 	if (!np || !dev)
 		return -EINVAL;
@@ -643,28 +684,7 @@ int of_reserved_mem_device_init_by_idx(struct device *dev,
 	rmem = of_reserved_mem_lookup(target);
 	of_node_put(target);
 
-	if (!rmem || !rmem->ops || !rmem->ops->device_init)
-		return -EINVAL;
-
-	rd = kmalloc_obj(struct rmem_assigned_device);
-	if (!rd)
-		return -ENOMEM;
-
-	ret = rmem->ops->device_init(rmem, dev);
-	if (ret == 0) {
-		rd->dev = dev;
-		rd->rmem = rmem;
-
-		mutex_lock(&of_rmem_assigned_device_mutex);
-		list_add(&rd->list, &of_rmem_assigned_device_list);
-		mutex_unlock(&of_rmem_assigned_device_mutex);
-
-		dev_info(dev, "assigned reserved memory node %s\n", rmem->name);
-	} else {
-		kfree(rd);
-	}
-
-	return ret;
+	return of_reserved_mem_device_init_with_mem(dev, rmem);
 }
 EXPORT_SYMBOL_GPL(of_reserved_mem_device_init_by_idx);
 
diff --git a/include/linux/of_reserved_mem.h b/include/linux/of_reserved_mem.h
index f573423359f48..12f7ddb7ee61f 100644
--- a/include/linux/of_reserved_mem.h
+++ b/include/linux/of_reserved_mem.h
@@ -32,6 +32,8 @@ typedef int (*reservedmem_of_init_fn)(struct reserved_mem *rmem);
 #define RESERVEDMEM_OF_DECLARE(name, compat, init)			\
 	_OF_DECLARE(reservedmem, name, compat, init, reservedmem_of_init_fn)
 
+int of_reserved_mem_device_init_with_mem(struct device *dev,
+					 struct reserved_mem *rmem);
 int of_reserved_mem_device_init_by_idx(struct device *dev,
 				       struct device_node *np, int idx);
 int of_reserved_mem_device_init_by_name(struct device *dev,
@@ -51,6 +53,12 @@ int of_reserved_mem_region_count(const struct device_node *np);
 #define RESERVEDMEM_OF_DECLARE(name, compat, init)			\
 	_OF_DECLARE_STUB(reservedmem, name, compat, init, reservedmem_of_init_fn)
 
+static inline int of_reserved_mem_device_init_with_mem(struct device *dev,
+						       struct reserved_mem *rmem)
+{
+	return -EOPNOTSUPP;
+}
+
 static inline int of_reserved_mem_device_init_by_idx(struct device *dev,
 					struct device_node *np, int idx)
 {
-- 
2.52.0