fdt: Add resource parsing functions

Add the fdt_get_resource() and fdt_get_named_resource() functions which
can be used to parse resources (memory regions) from an FDT. A helper to
compute the size of a region is also provided.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Simon Glass <sjg@chromium.org>

lib/fdtdec.c

@@ -708,4 +708,61 @@ int fdtdec_read_fmap_entry(const void *blob, int node, const char *name,
 
 	return 0;
 }
+
+static u64 fdtdec_get_number(const fdt32_t *ptr, unsigned int cells)
+{
+	u64 number = 0;
+
+	while (cells--)
+		number = (number << 32) | fdt32_to_cpu(*ptr++);
+
+	return number;
+}
+
+int fdt_get_resource(const void *fdt, int node, const char *property,
+		     unsigned int index, struct fdt_resource *res)
+{
+	const fdt32_t *ptr, *end;
+	int na, ns, len, parent;
+	unsigned int i = 0;
+
+	parent = fdt_parent_offset(fdt, node);
+	if (parent < 0)
+		return parent;
+
+	na = fdt_address_cells(fdt, parent);
+	ns = fdt_size_cells(fdt, parent);
+
+	ptr = fdt_getprop(fdt, node, property, &len);
+	if (!ptr)
+		return len;
+
+	end = ptr + len / sizeof(*ptr);
+
+	while (ptr + na + ns <= end) {
+		if (i == index) {
+			res->start = res->end = fdtdec_get_number(ptr, na);
+			res->end += fdtdec_get_number(&ptr[na], ns) - 1;
+			return 0;
+		}
+
+		ptr += na + ns;
+		i++;
+	}
+
+	return -FDT_ERR_NOTFOUND;
+}
+
+int fdt_get_named_resource(const void *fdt, int node, const char *property,
+			   const char *prop_names, const char *name,
+			   struct fdt_resource *res)
+{
+	int index;
+
+	index = fdt_find_string(fdt, node, prop_names, name);
+	if (index < 0)
+		return index;
+
+	return fdt_get_resource(fdt, node, property, index, res);
+}
 #endif