fdt/wrappers: Introduce code to find UART DT node
The stdout-path property in the /chosen node of a DTB points to a device
node, which is used for boot console output.
On most (if not all) ARM based platforms this is the debug UART.
The ST platform code contains a function to parse this property and
chase down eventual aliases to learn the node offset of this UART node.
Introduce a slightly more generalised version of this ST platform function
in the generic fdt_wrappers code. This will be useful for other platforms
as well.
Change-Id: Ie6da47ace7833861b5e35fe8cba49835db3659a5
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/common/fdt_wrappers.c b/common/fdt_wrappers.c
index 2c4b9c3..1901a20 100644
--- a/common/fdt_wrappers.c
+++ b/common/fdt_wrappers.c
@@ -294,3 +294,50 @@
return fdt_get_reg_props_by_index(dtb, node, index, base, size);
}
+
+/*******************************************************************************
+ * This function gets the stdout path node.
+ * It reads the value indicated inside the device tree.
+ * Returns node offset on success and a negative FDT error code on failure.
+ ******************************************************************************/
+int fdt_get_stdout_node_offset(const void *dtb)
+{
+ int node;
+ const char *prop, *path;
+ int len;
+
+ /* The /secure-chosen node takes precedence over the standard one. */
+ node = fdt_path_offset(dtb, "/secure-chosen");
+ if (node < 0) {
+ node = fdt_path_offset(dtb, "/chosen");
+ if (node < 0) {
+ return -FDT_ERR_NOTFOUND;
+ }
+ }
+
+ prop = fdt_getprop(dtb, node, "stdout-path", NULL);
+ if (prop == NULL) {
+ return -FDT_ERR_NOTFOUND;
+ }
+
+ /* Determine the actual path length, as a colon terminates the path. */
+ path = strchr(prop, ':');
+ if (path == NULL) {
+ len = strlen(prop);
+ } else {
+ len = path - prop;
+ }
+
+ /* Aliases cannot start with a '/', so it must be the actual path. */
+ if (prop[0] == '/') {
+ return fdt_path_offset_namelen(dtb, prop, len);
+ }
+
+ /* Lookup the alias, as this contains the actual path. */
+ path = fdt_get_alias_namelen(dtb, prop, len);
+ if (path == NULL) {
+ return -FDT_ERR_NOTFOUND;
+ }
+
+ return fdt_path_offset(dtb, path);
+}