servo_updater: Do not raise ServoUpdaterException on module importstabilize-12997.B-master

External tools such as platform/dev/contrib/dut-console may import
servo_updater as a module. On import time, this module will check the
existence of FIRMWARE_PATH and potentially raise ServoUpdaterException,
which is unnecessary if the function the importing program calls does
not have reference to the global variable FIRMWARE_PATH (for example,
find_available_version()).

In addition, there is only one function, findfiles(), that is currently
using FIRMWARE_PATH and other similar global variables. Therefore, move
the check for path existence inside findfiles(), so that
ServoUpdaterException will not be raised on module import time.

Also add servo board name constants to servo_updater to reduce duplicate
string literals.

BRANCH=none
BUG=chromium:1061354
TEST=Run 'sudo servod -b kukui -m jacuzzi' and make sure findfiles() is
     called without exceptions

Cq-Depend: chromium:2102179
Change-Id: I0179c44ba2a3947cb26035d97cd1ebeb453ef67a
Signed-off-by: Yu-Ping Wu <yupingso@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2102247
Reviewed-by: Wai-Hong Tam <waihong@google.com>

1 files changed, 33 insertions, 25 deletions

diff --git a/extra/usb_updater/servo_updater.py b/extra/usb_updater/servo_updater.py
index 7ef16658fd..415c38ea3d 100755
--- a/extra/usb_updater/servo_updater.py
+++ b/extra/usb_updater/servo_updater.py
@@ -21,6 +21,11 @@ import ecusb.tiny_servo_common as c
 class ServoUpdaterException(Exception):
   """Raised on exceptions generated by servo_updater."""
 
+BOARD_C2D2 = "c2d2"
+BOARD_SERVO_MICRO = "servo_micro"
+BOARD_SERVO_V4 = "servo_v4"
+BOARD_SWEETBERRY = "sweetberry"
+SERVO_BOARDS = (BOARD_C2D2, BOARD_SERVO_MICRO, BOARD_SERVO_V4, BOARD_SWEETBERRY)
 
 DEFAULT_BASE_PATH = '/usr/'
 TEST_IMAGE_BASE_PATH = '/usr/local/'
@@ -30,20 +35,6 @@ COMMON_PATH = 'share/servo_updater'
 FIRMWARE_DIR = "firmware/"
 CONFIGS_DIR = "configs/"
 
-if os.path.exists(os.path.join(DEFAULT_BASE_PATH, COMMON_PATH)):
-  BASE_PATH = DEFAULT_BASE_PATH
-elif os.path.exists(os.path.join(TEST_IMAGE_BASE_PATH, COMMON_PATH)):
-  BASE_PATH = TEST_IMAGE_BASE_PATH
-else:
-  raise ServoUpdaterException('servo_updater/ dir not found in known spots.')
-
-FIRMWARE_PATH = os.path.join(BASE_PATH, COMMON_PATH, FIRMWARE_DIR)
-CONFIGS_PATH = os.path.join(BASE_PATH, COMMON_PATH, CONFIGS_DIR)
-
-for p in [FIRMWARE_PATH, CONFIGS_PATH]:
-  if not os.path.exists(p):
-    raise ServoUpdaterException('Could not find required path %r' % p)
-
 def flash(brdfile, serialno, binfile):
   """Call fw_update to upload to updater USB endpoint."""
   p = fw_update.Supdate()
@@ -186,9 +177,23 @@ def findfiles(cname, fname):
   Returns:
     cname, fname: validated filenames selected from the path.
   """
+  for p in (DEFAULT_BASE_PATH, TEST_IMAGE_BASE_PATH):
+    updater_path = os.path.join(p, COMMON_PATH)
+    if os.path.exists(updater_path):
+      break
+  else:
+    raise ServoUpdaterException('servo_updater/ dir not found in known spots.')
+
+  firmware_path = os.path.join(updater_path, FIRMWARE_DIR)
+  configs_path = os.path.join(updater_path, CONFIGS_DIR)
+
+  for p in (firmware_path, configs_path):
+    if not os.path.exists(p):
+      raise ServoUpdaterException('Could not find required path %r' % p)
+
   if not os.path.isfile(cname):
     # If not an existing file, try checking on the default path.
-    newname = CONFIGS_PATH + cname
+    newname = os.path.join(configs_path, cname)
     if os.path.isfile(newname):
       cname = newname
     elif os.path.isfile(newname + ".json"):
@@ -198,17 +203,20 @@ def findfiles(cname, fname):
       raise ServoUpdaterException("Can't find file: %s." % cname)
 
   if not fname:
-    # If None, try defaults.
-    dev = None
-    for default_f in ['c2d2', 'servo_micro', 'servo_v4', 'sweetberry']:
-      if default_f in cname:
-        dev = default_f
-    if os.path.isfile(FIRMWARE_PATH + dev + ".bin"):
-      fname = FIRMWARE_PATH + dev + ".bin"
+    # If None, try to infer board name from config.
+    for board in SERVO_BOARDS:
+      if board in cname:
+        newname = os.path.join(firmware_path, board + ".bin")
+        if os.path.isfile(newname):
+          fname = newname
+          break
+    else:
+      raise ServoUpdaterException("Can't find firmware binary file")
   elif not os.path.isfile(fname):
     # If a name is specified but not found, try the default path.
-    if os.path.isfile(FIRMWARE_PATH + fname):
-      fname = FIRMWARE_PATH + fname
+    newname = os.path.join(firmware_path, fname)
+    if os.path.isfile(newname):
+      fname = newname
     else:
       raise ServoUpdaterException("Can't find file: %s." % fname)
 
@@ -239,7 +247,7 @@ def main():
   parser.add_argument('-s', '--serialno', type=str,
       help="serial number to program", default=None)
   parser.add_argument('-b', '--board', type=str,
-      help="Board configuration json file", default="servo_v4")
+      help="Board configuration json file", default=BOARD_SERVO_V4)
   parser.add_argument('-f', '--file', type=str,
       help="Complete ec.bin file", default=None)
   parser.add_argument('--force', action="store_true",