imgtool: update help message for slot-size
In case slot sizes are different, use the secondary slot (to use for
calculations, padding, etc).
@@ -260,7 +260,8 @@ class BasedIntParamType(click.ParamType):
@click.option('--pad', default=False, is_flag=True,
help='Pad image to --slot-size bytes, adding trailer magic')
@click.option('-S', '--slot-size', type=BasedIntParamType(), required=True,
- help='Size of the slot where the image will be written')
+ help='Size of the slot. If the slots have different sizes, use '
+ 'the size of the secondary slot.')
@click.option('--pad-header', default=False, is_flag=True,
help='Add --header-size zeroed bytes at the beginning of the '
'image')
