From: David Gibson <da...@gibson.dropbear.id.au>
Device trees can contain empty (zero length) properties, which are often
used as boolean flags. These can already be created using fdt_setprop()
passing a length of zero and a pointer which is ignored. It is safe to
pass NULL, but that may not be obvious from the interface. To make it
clearer, add an fdt_setprop_empty() helper macro.
Signed-off-by: David Gibson <da...@gibson.dropbear.id.au>
---
cpukit/include/libfdt.h | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)
diff --git a/cpukit/include/libfdt.h b/cpukit/include/libfdt.h
index c69e918899..ac42e04595 100644
--- a/cpukit/include/libfdt.h
+++ b/cpukit/include/libfdt.h
@@ -1527,6 +1527,36 @@ static inline int fdt_setprop_cell(void *fdt, int
nodeoffset, const char *name,
#define fdt_setprop_string(fdt, nodeoffset, name, str) \
fdt_setprop((fdt), (nodeoffset), (name), (str), strlen(str)+1)
+
+/**
+ * fdt_setprop_empty - set a property to an empty value
+ * @fdt: pointer to the device tree blob
+ * @nodeoffset: offset of the node whose property to change
+ * @name: name of the property to change
+ *
+ * fdt_setprop_empty() sets the value of the named property in the
+ * given node to an empty (zero length) value, or creates a new empty
+ * property if it does not already exist.
+ *
+ * This function may insert or delete data from the blob, and will
+ * therefore change the offsets of some existing nodes.
+ *
+ * returns:
+ * 0, on success
+ * -FDT_ERR_NOSPACE, there is insufficient free space in the blob to
+ * contain the new property value
+ * -FDT_ERR_BADOFFSET, nodeoffset did not point to FDT_BEGIN_NODE tag
+ * -FDT_ERR_BADLAYOUT,
+ * -FDT_ERR_BADMAGIC,
+ * -FDT_ERR_BADVERSION,
+ * -FDT_ERR_BADSTATE,
+ * -FDT_ERR_BADSTRUCTURE,
+ * -FDT_ERR_BADLAYOUT,
+ * -FDT_ERR_TRUNCATED, standard meanings
+ */
+#define fdt_setprop_empty(fdt, nodeoffset, name) \
+ fdt_setprop((fdt), (nodeoffset), (name), NULL, 0)
+
/**
* fdt_appendprop - append to or create a property
* @fdt: pointer to the device tree blob
--
2.13.7
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