tools: Improve comments in signing functions
Add some more comments to explain what is going on in the signing
functions. Fix two repeated typos.
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/image.h b/include/image.h
index fe13562..15cfb2c 100644
--- a/include/image.h
+++ b/include/image.h
@@ -1025,7 +1025,7 @@
* fit_add_verification_data() - add verification data to FIT image nodes
*
* @keydir: Directory containing keys
- * @kwydest: FDT blob to write public key information to
+ * @kwydest: FDT blob to write public key information to (NULL if none)
* @fit: Pointer to the FIT format image header
* @comment: Comment to add to signature nodes
* @require_keys: Mark all keys as 'required'