fdt: Add a function to get the alias sequence of a node

Aliases are used to provide U-Boot's numbering of devices, such as:

aliases {
	spi0 = "/spi@12330000";
}

spi@12330000 {
	...
}

This tells us that the SPI controller at 12330000 is considered to be the
first SPI controller (SPI 0). So we have a numbering for the SPI node.

Add a function that returns the numbering for a node assume that it exists
in the list of aliases.

Signed-off-by: Simon Glass <sjg@chromium.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/include/fdtdec.h b/include/fdtdec.h
index a7e6ee7fdf..f454f7e217 100644
--- a/include/fdtdec.h
+++ b/include/fdtdec.h
@@ -345,6 +345,24 @@ int fdtdec_find_aliases_for_id(const void *blob, const char *name,
 int fdtdec_add_aliases_for_id(const void *blob, const char *name,
 			enum fdt_compat_id id, int *node_list, int maxcount);
 
+/**
+ * Get the alias sequence number of a node
+ *
+ * This works out whether a node is pointed to by an alias, and if so, the
+ * sequence number of that alias. Aliases are of the form <base><num> where
+ * <num> is the sequence number. For example spi2 would be sequence number
+ * 2.
+ *
+ * @param blob		Device tree blob (if NULL, then error is returned)
+ * @param base		Base name for alias (before the underscore)
+ * @param node		Node to look up
+ * @param seqp		This is set to the sequence number if one is found,
+ *			but otherwise the value is left alone
+ * @return 0 if a sequence was found, -ve if not
+ */
+int fdtdec_get_alias_seq(const void *blob, const char *base, int node,
+			 int *seqp);
+
 /*
  * Get the name for a compatible ID
  *