[Mellanox] enhance the reboot cause handling on 201811 (#3253)

* [Mellanox/mlnx-platform-api] enable mellanox's platform-api to be loaded as a whole.

* [chassis] update reboot-cause handling code to adapt the hw-management currently running on 201811

* [chassis]handle the case that reboot cause file can be any dir matching pattern "hwmonX".

Author: stephenxs

platform/mellanox/mlnx-platform-api/sonic_platform/__init__.py

@@ -0,0 +1,2 @@
+__all__ = ["platform", "chassis"]
+from sonic_platform import *

platform/mellanox/mlnx-platform-api/sonic_platform/chassis.py

@@ -13,17 +13,22 @@
 try:
     from sonic_platform_base.chassis_base import ChassisBase
     from os.path import join
+    from glob import glob
+    import os
     import io
     import re
     import subprocess
     import syslog
 except ImportError as e:
     raise ImportError (str(e) + "- required module not found")
 
+# The default dir for reboot cause files
 HWMGMT_SYSTEM_ROOT = '/var/run/hw-management/system/'
+# The hwmon root dir used in case of the hw-mgmt v1.x.x is used.
+HWMON_ROOT_PATTERN = '/sys/devices/platform/mlxplat/mlxreg-io/hwmon/hwmon*'
 
 #reboot cause related definitions
-REBOOT_CAUSE_ROOT = HWMGMT_SYSTEM_ROOT
+REBOOT_CAUSE_ROOT = None
 
 REBOOT_CAUSE_POWER_LOSS_FILE = 'reset_main_pwr_fail'
 REBOOT_CAUSE_AUX_POWER_LOSS_FILE = 'reset_aux_pwr_or_ref'
@@ -37,18 +42,37 @@
 
 # ========================== Syslog wrappers ==========================
 SYSLOG_IDENTIFIER = "mlnx-chassis"
-def log_warning(msg, also_print_to_console=False):
+def log_warning(msg):
     syslog.openlog(SYSLOG_IDENTIFIER)
     syslog.syslog(syslog.LOG_WARNING, msg)
     syslog.closelog()
 
+def log_info(msg):
+    syslog.openlog(SYSLOG_IDENTIFIER)
+    syslog.syslog(syslog.LOG_INFO, msg)
+    syslog.closelog()
 
 class Chassis(ChassisBase):
     """Platform-specific Chassis class"""
 
     def __init__(self):
+        global REBOOT_CAUSE_ROOT
         super(Chassis, self).__init__()
 
+        # adaptively reboot cause root dir initialization
+        REBOOT_CAUSE_ROOT = HWMGMT_SYSTEM_ROOT
+        if not os.path.exists(REBOOT_CAUSE_ROOT):
+            log_warning("reboot cause dir {} doesn't exist, trying other alternatives".format(REBOOT_CAUSE_ROOT))
+            possible_reboot_cause_dir_list = glob(HWMON_ROOT_PATTERN)
+            if possible_reboot_cause_dir_list is None or len(possible_reboot_cause_dir_list) == 0:
+                log_warning("can't find reboot cause files in {}".format(HWMON_ROOT_PATTERN))
+            else:
+                REBOOT_CAUSE_ROOT = possible_reboot_cause_dir_list[0]
+                if len(possible_reboot_cause_dir_list) > 1:
+                    log_warning("found multiple reboot cause dir {}, pick the first one".format(possible_reboot_cause_dir_list))
+                else:
+                    log_info("pick {} as reboot cause file".format(REBOOT_CAUSE_ROOT))
+
     def _read_generic_file(self, filename, len):
         """
         Read a generic file, returns the contents of the file