libfdt: Add overlay application function
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@free-electrons.com>
diff --git a/include/libfdt.h b/include/libfdt.h
index 4c56711c..b6a400a 100644
--- a/include/libfdt.h
+++ b/include/libfdt.h
@@ -1740,6 +1740,36 @@
*/
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, the phandles in the overlay do not have the right
+ * magic
+ * -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 */
/**********************************************************************/