binman: Add info to allow safely repacking an image later

At present it is not possible to discover the contraints to repacking an
image (e.g. maximum section size) since this information is not preserved
from the original image description.

Add new 'orig-offset' and 'orig-size' properties to hold this. Add them to
the main device tree in the image.

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

1 files changed, 23 insertions, 0 deletions

diff --git a/tools/binman/README b/tools/binman/README
index 3522354519..6a1cd110a4 100644
--- a/tools/binman/README
+++ b/tools/binman/README
@@ -481,6 +481,29 @@ name-prefix:
 	distinguish binaries with otherwise identical names.
 
 
+Image Properties
+----------------
+
+Image nodes act like sections but also have a few extra properties:
+
+filename:
+	Output filename for the image. This defaults to image.bin (or in the
+	case of multiple images <nodename>.bin where <nodename> is the name of
+	the image node.
+
+allow-repack:
+	Create an image that can be repacked. With this option it is possible
+	to change anything in the image after it is created, including updating
+	the position and size of image components. By default this is not
+	permitted since it is not possibly to know whether this might violate a
+	constraint in the image description. For example, if a section has to
+	increase in size to hold a larger binary, that might cause the section
+	to fall out of its allow region (e.g. read-only portion of flash).
+
+	Adding this property causes the original offset and size values in the
+	image description to be stored in the FDT and fdtmap.
+
+
 Entry Documentation
 -------------------