drivers/of: Return allocated memory from of_fdt_unflatten_tree()

This returns the allocate memory chunk, storing the unflattened device
tree, from of_fdt_unflatten_tree() so that memory chunk can be released
on demand in PowerNV PCI hotplug driver.

Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>

drivers/of/fdt.c

@@ -454,11 +454,14 @@ static int unflatten_dt_nodes(const void *blob,
  * @mynodes: The device_node tree created by the call
  * @dt_alloc: An allocator that provides a virtual address to memory
  * for the resulting tree
+ *
+ * Returns NULL on failure or the memory chunk containing the unflattened
+ * device tree on success.
  */
-static void __unflatten_device_tree(const void *blob,
-			     struct device_node *dad,
-			     struct device_node **mynodes,
-			     void * (*dt_alloc)(u64 size, u64 align))
+static void *__unflatten_device_tree(const void *blob,
+				     struct device_node *dad,
+				     struct device_node **mynodes,
+				     void *(*dt_alloc)(u64 size, u64 align))
 {
 	int size;
 	void *mem;
@@ -467,7 +470,7 @@ static void __unflatten_device_tree(const void *blob,
 
 	if (!blob) {
 		pr_debug("No device tree pointer\n");
-		return;
+		return NULL;
 	}
 
 	pr_debug("Unflattening device tree:\n");
@@ -477,13 +480,13 @@ static void __unflatten_device_tree(const void *blob,
 
 	if (fdt_check_header(blob)) {
 		pr_err("Invalid device tree blob header\n");
-		return;
+		return NULL;
 	}
 
 	/* First pass, scan for size */
 	size = unflatten_dt_nodes(blob, NULL, dad, NULL);
 	if (size < 0)
-		return;
+		return NULL;
 
 	size = ALIGN(size, 4);
 	pr_debug("  size is %d, allocating...\n", size);
@@ -503,6 +506,7 @@ static void __unflatten_device_tree(const void *blob,
 			   be32_to_cpup(mem + size));
 
 	pr_debug(" <- unflatten_device_tree()\n");
+	return mem;
 }
 
 static void *kernel_tree_alloc(u64 size, u64 align)
@@ -522,14 +526,21 @@ static DEFINE_MUTEX(of_fdt_unflatten_mutex);
  * tree of struct device_node. It also fills the "name" and "type"
  * pointers of the nodes so the normal device-tree walking functions
  * can be used.
+ *
+ * Returns NULL on failure or the memory chunk containing the unflattened
+ * device tree on success.
  */
-void of_fdt_unflatten_tree(const unsigned long *blob,
-			struct device_node *dad,
-			struct device_node **mynodes)
+void *of_fdt_unflatten_tree(const unsigned long *blob,
+			    struct device_node *dad,
+			    struct device_node **mynodes)
 {
+	void *mem;
+
 	mutex_lock(&of_fdt_unflatten_mutex);
-	__unflatten_device_tree(blob, dad, mynodes, &kernel_tree_alloc);
+	mem = __unflatten_device_tree(blob, dad, mynodes, &kernel_tree_alloc);
 	mutex_unlock(&of_fdt_unflatten_mutex);
+
+	return mem;
 }
 EXPORT_SYMBOL_GPL(of_fdt_unflatten_tree);
 

include/linux/of_fdt.h

@@ -37,9 +37,9 @@ extern bool of_fdt_is_big_endian(const void *blob,
 				 unsigned long node);
 extern int of_fdt_match(const void *blob, unsigned long node,
 			const char *const *compat);
-extern void of_fdt_unflatten_tree(const unsigned long *blob,
-			       struct device_node *dad,
-			       struct device_node **mynodes);
+extern void *of_fdt_unflatten_tree(const unsigned long *blob,
+				   struct device_node *dad,
+				   struct device_node **mynodes);
 
 /* TBD: Temporary export of fdt globals - remove when code fully merged */
 extern int __initdata dt_root_addr_cells;