Ability to pad images til a certain sizestm

In some cases it's convenient to pad the image, to avoid extra steps to
be able to write to flash. For example. The default settings on STM
Nucleo F401RE doesn't allow to write a part of a sector, which is
something we would like to do when adding the boot image trailer at the
correct location. The --pad parameter will add pad your image til the
size (N) you give as parameter. Currently it also always add the boot
image trailer if you use this command. So you will end up with this:

	 0            N-8                  N
	 | data | pad | boot_image_trailer |

Signed-off-by: Joakim Bech <joakim.bech@linaro.org>

2 files changed, 31 insertions, 0 deletions

diff --git a/newtimg.py b/newtimg.py
index 1c5c7a9..4f87e4d 100644
--- a/newtimg.py
+++ b/newtimg.py
@@ -1,3 +1,4 @@
+BOOT_IMG_MAGIC =                0x12344321
 IMAGE_MAGIC =			0x96f3b83c
 IMAGE_MAGIC_NONE =		0xffffffff
 
diff --git a/zep2newt.py b/zep2newt.py
index 3ae3601..772a0c2 100755
--- a/zep2newt.py
+++ b/zep2newt.py
@@ -40,6 +40,9 @@ def get_args():
                         default=str(hex(OFFSET_VECTOR_TABLE)), \
                         help='Offset to vector table in HEX')
 
+    parser.add_argument('--pad', required=False, \
+                        help='Pad file with 0xff up to this size (in hex)')
+
     parser.add_argument('--bit', required=False, \
                         help='Flash boot image trailer magic')
 
@@ -288,6 +291,28 @@ def create_jlink_clear_bit_script(bit_file, bitoffset="0x7bff8"):
     except IOError:
         print("[ERROR]: Cannot create to %s" % (jlink_file))
         sys.exit(1)
+################################################################################
+def pad_binary(binary_file, pad_size, boot_magic=False):
+    try:
+        # Get the correct size for the image
+        size = pad_size - os.path.getsize(binary_file)
+        if boot_magic:
+            size -= 8
+
+        if size <= 0:
+            print("Nothing to pad\n")
+            return
+
+        with open(binary_file, "ab") as f:
+            f.write(('\xff') * size)
+            if boot_magic:
+                f.write(struct.pack('I', BOOT_IMG_MAGIC) )
+                f.write(('\xff') * 4)
+            f.close()
+
+    except (OSError, IOError):
+        print("[ERROR]: Cannot open/append to %s" % (binary_file))
+        sys.exit(1)
 
 ################################################################################
 def main(argv):
@@ -300,6 +325,11 @@ def main(argv):
         global DEBUG
         DEBUG = True
 
+    if (args.pad):
+        pad_size = int(args.pad, 16)
+        pad_binary(args.binary_file, pad_size, True)
+        sys.exit(1)
+
     # Since it's a hex string, let's convert to an integer instead
     vtable_offs = int(args.vtable_offs, 16)