misc: Use a Makefile to ensure util/packet_pb2.py is up to date.

Rather than just ensuring that packet_pb2.py is available in general, use a
Makefile to ensure that it's also up to date in case packet.proto has
changed.

Also, remove a check that ensures that the protobuf module is available,
since python will complain if it needs it and can't find it.

Finally, remove a comment which talks about manually regenerating the
packet_pb2.py module, something that hasn't been necessary for a while, even
with the old version of this code.

Change-Id: I40c5c1f577e6d7ad1af9a209309a1eb92f073317
Reviewed-on: https://gem5-review.googlesource.com/5005
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

util/Makefile

@@ -0,0 +1,4 @@
+PROTO_PATH=../src/proto
+
+packet_pb2.py: $(PROTO_PATH)/packet.proto
+	protoc --python_out=. --proto_path=$(PROTO_PATH) $<

util/decode_packet_trace.py

@@ -38,45 +38,17 @@
 # Authors: Andreas Hansson
 
 # This script is used to dump protobuf packet traces to ASCII
-# format. It assumes that protoc has been executed and already
-# generated the Python package for the packet messages. This can
-# be done manually using:
-# protoc --python_out=. --proto_path=src/proto src/proto/packet.proto
-#
-# The ASCII trace format uses one line per request on the format cmd,
-# addr, size, tick,flags. For example:
-# r,128,64,4000,0
-# w,232123,64,500000,0
+# format.
 
+import os
 import protolib
+import subprocess
 import sys
 
-# Import the packet proto definitions. If they are not found, attempt
-# to generate them automatically.
-try:
-    import packet_pb2
-except:
-    print "Did not find packet proto definitions, attempting to generate"
-    import os
-    util_dir = os.path.dirname(os.path.realpath(__file__))
-    proto_dir = os.path.join(os.path.dirname(util_dir), 'src', 'proto')
-    proto_file = os.path.join(proto_dir, 'packet.proto')
-    from subprocess import call
-    error = call(['protoc', '--python_out=' + util_dir,
-                  '--proto_path=' + proto_dir, proto_file])
-    if not error:
-        print "Generated packet proto definitions"
-
-        try:
-            import google.protobuf
-        except:
-            print "Please install Python protobuf module"
-            exit(-1)
-
-        import packet_pb2
-    else:
-        print "Failed to import packet proto definitions"
-        exit(-1)
+util_dir = os.path.dirname(os.path.realpath(__file__))
+# Make sure the proto definitions are up to date.
+subprocess.check_call(['make', '--quiet', '-C', util_dir, 'packet_pb2.py'])
+import packet_pb2
 
 def main():
     if len(sys.argv) != 3: