[Mellanox] Enhance check_sysfs to ignore expected broken symbol links (…

…#4279)

With the Mellanox new hw-managenet package release V.7.0010.3134, some symbol links are expected to be broken after boot up, they should be excluded from the broken symbol link check. Add a function to match these expected broken symbol links and remove them from the check list.

tests/platform_tests/mellanox/check_sysfs.py

@@ -4,12 +4,38 @@
 This script contains re-usable functions for checking status of hw-management related sysfs.
 """
 import logging
+import re
 from tests.common.mellanox_data import get_platform_data
 from tests.common.utilities import wait_until
 
 MAX_FAN_SPEED_THRESHOLD = 0.15
 
 
+def skip_ignored_broken_symbolinks(broken_symbolinks):
+    """
+    @summary: Check all the broken symbol links found, remove the expected ones
+    examples for the expected broken symbol links:
+      /var/run/hw-management/led/led_psu2_green_delay_off
+      /var/run/hw-management/led/led_uid_blue_delay_on
+      /var/run/hw-management/led/led_fan_green_delay_on
+      /var/run/hw-management/led/led_status_red_delay_on
+    """
+    # Currently some led blinking related sysfs are expected to be broken after system boot up,
+    # so skip and remove them from the check list.
+    broken_symbolinks_updated = []
+    pattern = re.compile(".*led_.*_delay_(off|on)")
+
+    logging.info("broken_symbolinks: {}".format(broken_symbolinks))
+
+    for symbolink in broken_symbolinks.splitlines():
+        if not pattern.match(symbolink):
+            broken_symbolinks_updated.append(symbolink)
+        else:
+            logging.info("ignore expected broken link: {}".format(symbolink))
+
+    return broken_symbolinks_updated
+
+
 def check_sysfs(dut):
     """
     @summary: Check various hw-management related sysfs under /var/run/hw-management
@@ -21,8 +47,9 @@ def check_sysfs(dut):
 
     logging.info("Check broken symbolinks")
     broken_symbolinks = sysfs_facts['symbolink_info']['broken_links']
-    assert len(broken_symbolinks) == 0, \
-        "Found some broken symbolinks: {}".format(str(broken_symbolinks))
+    broken_symbolinks_updated = skip_ignored_broken_symbolinks(broken_symbolinks)
+    assert len(broken_symbolinks_updated) == 0, \
+        "Found some broken symbolinks: {}".format(str(broken_symbolinks_updated))
 
     logging.info("Check ASIC related sysfs")
     try: