reset.py: Not every Unix is Linux.

Move the sysfs tests for Maple out of unix_get_maple_path() and into a
new linux_get_maple_path(). This prevents unnecessary probing for a
nonexistent /sys on e.g. OS X.

Signed-off-by: Marti Bolivar <mbolivar@leaflabs.com>

1 files changed, 20 insertions, 8 deletions

diff --git a/support/scripts/reset.py b/support/scripts/reset.py
index bfc91e1..67a72c1 100755
--- a/support/scripts/reset.py
+++ b/support/scripts/reset.py
@@ -9,16 +9,28 @@ import sys
 import time
 from struct import pack
 
-def unix_get_maple_path(file_prefix):
-    """Try to find the device file for the Maple on *nix; assuming
-    that it looks like /dev/<file_prefix>* and has the correct ID in
-    the /sys tree.  If there are multiple possibilities, ask the user
-    what to do.  If the user chooses not to say, returns None."""
+def unix_get_maple_path(file_prefix, dev_is_maple=lambda dev: True):
+    """Try to find the device file for the Maple on *nix.
+
+    This function works assuming that the device file globs like
+    '/dev/<file_prefix>*'. The caller may pass an additional
+    dev_is_maple predicate if the platform supports additional tests
+    to determine if a device is a Maple.
+
+    If there are multiple possibilities, ask the user what to do.  If
+    the user chooses not to say, returns None."""
     possible_paths = [os.path.join('/dev', x) for x in os.listdir('/dev') \
-                          if (x.startswith(file_prefix) and tty_is_maple(x))]
+                      if x.startswith(file_prefix) and dev_is_maple(x)]
     return choose_path(possible_paths)
 
-def tty_is_maple(device):
+def linux_get_maple_path(file_prefix='ttyACM'):
+    """Specialized unix_get_maple_path() for Linux.
+
+    Attempts to check that a candidate device has the correct ID in
+    the /sys tree when deciding if it's a Maple."""
+    return unix_get_maple_path(file_prefix, linux_tty_is_maple)
+
+def linux_tty_is_maple(device):
     try:
         sysfile = open("/sys/class/tty/%s/device/uevent" % device, "r")
         text = "".join(sysfile.readlines())
@@ -72,7 +84,7 @@ def choose_among_options(options):
 plat_sys = platform.system()
 plat_bits = platform.architecture()[0]
 if plat_sys == 'Linux':
-    maple_path = unix_get_maple_path('ttyACM')
+    maple_path = linux_get_maple_path()
     # fall back on /dev/maple if that doesn't work
     if maple_path is None:
         maple_path = '/dev/maple'