cros_ec: Add a function for reading a flash map entry

A flash map describes the layout of flash memory in terms of offsets and
sizes for each region. Add a function to read a flash map entry from the
device tree.

Reviewed-by: Che-Liang Chiou <clchiou@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>

include/fdtdec.h

@@ -530,4 +530,22 @@ const u8 *fdtdec_locate_byte_array(const void *blob, int node,
  */
 int fdtdec_decode_region(const void *blob, int node,
 		const char *prop_name, void **ptrp, size_t *size);
+
+/* A flash map entry, containing an offset and length */
+struct fmap_entry {
+	uint32_t offset;
+	uint32_t length;
+};
+
+/**
+ * Read a flash entry from the fdt
+ *
+ * @param blob		FDT blob
+ * @param node		Offset of node to read
+ * @param name		Name of node being read
+ * @param entry		Place to put offset and size of this node
+ * @return 0 if ok, -ve on error
+ */
+int fdtdec_read_fmap_entry(const void *blob, int node, const char *name,
+			   struct fmap_entry *entry);
 #endif

lib/fdtdec.c

@@ -617,3 +617,27 @@ int fdtdec_decode_region(const void *blob, int node,
 	debug("%s: size=%zx\n", __func__, *size);
 	return 0;
 }
+
+/**
+ * Read a flash entry from the fdt
+ *
+ * @param blob		FDT blob
+ * @param node		Offset of node to read
+ * @param name		Name of node being read
+ * @param entry		Place to put offset and size of this node
+ * @return 0 if ok, -ve on error
+ */
+int fdtdec_read_fmap_entry(const void *blob, int node, const char *name,
+			   struct fmap_entry *entry)
+{
+	u32 reg[2];
+
+	if (fdtdec_get_int_array(blob, node, "reg", reg, 2)) {
+		debug("Node '%s' has bad/missing 'reg' property\n", name);
+		return -FDT_ERR_NOTFOUND;
+	}
+	entry->offset = reg[0];
+	entry->length = reg[1];
+
+	return 0;
+}