[efi] Expose efi_path_next() utility function

Provide a single central implementation of the logic for stepping
through elements of an EFI device path.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 29 insertions, 5 deletions

diff --git a/src/interface/efi/efi_path.c b/src/interface/efi/efi_path.c
index 1a95a3b9..937d3c70 100644
--- a/src/interface/efi/efi_path.c
+++ b/src/interface/efi/efi_path.c
@@ -41,18 +41,42 @@
  */
 
 /**
+ * Find next element in device path
+ *
+ * @v path		Device path, or NULL
+ * @v next		Next element in device path, or NULL if at end
+ */
+EFI_DEVICE_PATH_PROTOCOL * efi_path_next ( EFI_DEVICE_PATH_PROTOCOL *path ) {
+
+	/* Check for non-existent device path */
+	if ( ! path )
+		return NULL;
+
+	/* Check for end of device path */
+	if ( path->Type == END_DEVICE_PATH_TYPE )
+		return NULL;
+
+	/* Move to next component of the device path */
+	path = ( ( ( void * ) path ) +
+		 /* There's this amazing new-fangled thing known as
+		  * a UINT16, but who wants to use one of those? */
+		 ( ( path->Length[1] << 8 ) | path->Length[0] ) );
+
+	return path;
+}
+
+/**
  * Find end of device path
  *
  * @v path		Device path, or NULL
  * @ret path_end	End of device path, or NULL
  */
 EFI_DEVICE_PATH_PROTOCOL * efi_path_end ( EFI_DEVICE_PATH_PROTOCOL *path ) {
+	EFI_DEVICE_PATH_PROTOCOL *next;
 
-	while ( path && ( path->Type != END_DEVICE_PATH_TYPE ) ) {
-		path = ( ( ( void * ) path ) +
-			 /* There's this amazing new-fangled thing known as
-			  * a UINT16, but who wants to use one of those? */
-			 ( ( path->Length[1] << 8 ) | path->Length[0] ) );
+	/* Find end of device path */
+	while ( ( next = efi_path_next ( path ) ) != NULL ) {
+		path = next;
 	}
 
 	return path;