tools/checksum: fix input from stdin

argparse is supposed to take care of this automatically, but it wasn't
working due to the fact that argparse ignores the binary specifier
for stdin.

Author: dlech

tools/checksum.py

@@ -10,6 +10,7 @@
 
 import argparse
 import struct
+import sys
 
 
 def sum_complement(fw, max_size):
@@ -133,6 +134,13 @@ def crc32_checksum(fw, max_size):
 
     args = parser.parse_args()
 
+    # argparse doesn't know how to handle "rb" for stdin and gives us TextIO
+    # instead of BinaryIO
+    if args.fw_file == sys.stdin:
+        if sys.stdin.isatty():
+            raise RuntimeError("expecting data to be piped via stdin")
+        args.fw_file = sys.stdin.buffer
+
     if args.checksum_type == "xor":
         print(hex(sum_complement(args.fw_file, args.max_size)))
     elif args.checksum_type == "crc32":