[PATCH 16/45] libfdt: Add overlay application function

[Sebastian Huber]

From: Maxime Ripard <maxime.ripard at free-electrons.com>

The device tree overlays are a good way to deal with user-modifyable
boards or boards with some kind of an expansion mechanism where we can
easily plug new board in (like the BBB, the Raspberry Pi or the CHIP).

Add a new function to merge overlays with a base device tree.

Signed-off-by: Maxime Ripard <maxime.ripard at free-electrons.com>
Signed-off-by: David Gibson <david at gibson.dropbear.id.au>
---
 cpukit/include/libfdt.h     | 31 +++++++++++++++++++++++++++++++
 cpukit/include/libfdt_env.h |  1 +
 2 files changed, 32 insertions(+)

diff --git a/cpukit/include/libfdt.h b/cpukit/include/libfdt.h
index d2e5e031fb..c69e918899 100644
--- a/cpukit/include/libfdt.h
+++ b/cpukit/include/libfdt.h
@@ -1763,6 +1763,37 @@ int fdt_add_subnode(void *fdt, int parentoffset, const char *name);
  */
 int fdt_del_node(void *fdt, int nodeoffset);
 
+/**
+ * fdt_overlay_apply - Applies a DT overlay on a base DT
+ * @fdt: pointer to the base device tree blob
+ * @fdto: pointer to the device tree overlay blob
+ *
+ * fdt_overlay_apply() will apply the given device tree overlay on the
+ * given base device tree.
+ *
+ * Expect the base device tree to be modified, even if the function
+ * returns an error.
+ *
+ * returns:
+ *	0, on success
+ *	-FDT_ERR_NOSPACE, there's not enough space in the base device tree
+ *	-FDT_ERR_NOTFOUND, the overlay points to some inexistant nodes or
+ *		properties in the base DT
+ *	-FDT_ERR_BADPHANDLE,
+ *	-FDT_ERR_BADOVERLAY,
+ *	-FDT_ERR_NOPHANDLES,
+ *	-FDT_ERR_INTERNAL,
+ *	-FDT_ERR_BADLAYOUT,
+ *	-FDT_ERR_BADMAGIC,
+ *	-FDT_ERR_BADOFFSET,
+ *	-FDT_ERR_BADPATH,
+ *	-FDT_ERR_BADVERSION,
+ *	-FDT_ERR_BADSTRUCTURE,
+ *	-FDT_ERR_BADSTATE,
+ *	-FDT_ERR_TRUNCATED, standard meanings
+ */
+int fdt_overlay_apply(void *fdt, void *fdto);
+
 /**********************************************************************/
 /* Debugging / informational functions                                */
 /**********************************************************************/
diff --git a/cpukit/include/libfdt_env.h b/cpukit/include/libfdt_env.h
index 9dea97dfff..99f936dacc 100644
--- a/cpukit/include/libfdt_env.h
+++ b/cpukit/include/libfdt_env.h
@@ -54,6 +54,7 @@
 
 #include <stddef.h>
 #include <stdint.h>
+#include <stdlib.h>
 #include <string.h>
 
 #ifdef __CHECKER__
-- 
2.13.7