CR50: update tpmtest.py to handle a success command code

Update tpmtest.py to handle a success command code
(i.e. return value of 0) as per change
12da6c23fb

This change makes the test suite runnable (not all
tests pass though - sha and upgrade tests are broken).

Also rename local variable subcmd to avoid a name collision.

BUG=none
BRANCH=none
TEST=tpmtest.py passes, except for sha & upgrade

Change-Id: I927ead775a1e41b9abf9f905b9f191e8bd5e108b
Signed-off-by: nagendra modadugu <ngm@google.com>
Reviewed-on: https://chromium-review.googlesource.com/411535
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>

test/tpm_test/tpmtest.py

@@ -73,7 +73,12 @@ class TPM(object):
     if size > 4096:
       raise subcmd.TpmTestError(prefix + 'invalid size %d' % size)
     if response_mode:
-      return
+      # Startup response code or extension command response code
+      if cmd_code == 0x100 or cmd_code == 0:
+        return
+      else:
+        raise subcmd.TpmTestError(
+          prefix + 'invalid command code 0x%x' % cmd_code)
     if cmd_code >= 0x11f and cmd_code <= 0x18f:
       return  # This is a valid command
     if cmd_code == EXT_CMD:
@@ -111,16 +116,16 @@ class TPM(object):
         error message describes the problem.
     """
     header_size = struct.calcsize(self.HEADER_FMT)
-    tag, size, cmd, subcmd = struct.unpack(self.HEADER_FMT,
+    tag, size, cmd, sub = struct.unpack(self.HEADER_FMT,
                                            response[:header_size])
     if tag != 0x8001:
       raise subcmd.TpmTestError('Wrong response tag: %4.4x' % tag)
-    if cmd != EXT_CMD:
+    if cmd:
       raise subcmd.TpmTestError('Unexpected response command field: %8.8x' %
                                 cmd)
-    if subcmd != expected_subcmd:
+    if sub != expected_subcmd:
       raise subcmd.TpmTestError('Unexpected response subcommand field: %2.2x' %
-                     subcmd)
+                     sub)
     if size != len(response):
       raise subcmd.TpmTestError('Size mismatch: header %d, actual %d' % (
           size, len(response)))