[ModuleBase] Add get_midplane_down_reason() API and MIDPLANE_DOWN_REASON_* constants

sonic_platform_base/module_base.py

@@ -71,6 +71,20 @@ class ModuleBase(device_base.DeviceBase):
     # Module reboot type to reboot SMART SWITCH
     MODULE_REBOOT_SMARTSWITCH = "SMARTSWITCH"
 
+    # Possible midplane down reasons for SmartSwitch.
+    MIDPLANE_DOWN_REASON_POWER_LOSS = "Power Loss"
+    MIDPLANE_DOWN_REASON_THERMAL_OVERLOAD_CPU = "Thermal Overload: CPU"
+    MIDPLANE_DOWN_REASON_THERMAL_OVERLOAD_ASIC = "Thermal Overload: ASIC"
+    MIDPLANE_DOWN_REASON_THERMAL_OVERLOAD_OTHER = "Thermal Overload: Other"
+    MIDPLANE_DOWN_REASON_INSUFFICIENT_FAN_SPEED = "Insufficient Fan Speed"
+    MIDPLANE_DOWN_REASON_WATCHDOG = "Watchdog"
+    MIDPLANE_DOWN_REASON_HARDWARE_OTHER = "Hardware - Other"
+    MIDPLANE_DOWN_REASON_HARDWARE_BIOS = "BIOS"
+    MIDPLANE_DOWN_REASON_HARDWARE_CPU = "CPU"
+    MIDPLANE_DOWN_REASON_HARDWARE_BUTTON = "Push button"
+    MIDPLANE_DOWN_REASON_HARDWARE_RESET_FROM_ASIC = "Reset from ASIC"
+    MIDPLANE_DOWN_REASON_NON_HARDWARE = "Non-Hardware"
+
     def __init__(self):
         # List of ComponentBase-derived objects representing all components
         # available on the module
@@ -1097,6 +1111,19 @@ def get_midplane_ip(self):
         """
         raise NotImplementedError
 
+    def get_midplane_down_reason(self):
+        """
+         Retrieves the midplane down reason.
+
+        Returns:
+            A tuple (string, string) where the first element is a string
+            containing the midplane down reason. This string must
+            be one of the predefined strings in this class. If the first
+            string is "MIDPLANE_DOWN_REASON_HARDWARE_OTHER", the second string can be
+            used to pass a description of the midplane down reason.
+        """
+        raise NotImplementedError
+
     def is_midplane_reachable(self):
         """
         Retrieves the reachability status of the module from the Supervisor or

tests/module_base_test.py

@@ -39,7 +39,7 @@ def teardown_method(self):
     @pytest.mark.parametrize(
         "method_name",
         ["get_dpu_id", "get_reboot_cause", "get_state_info", "get_pci_bus_info", "pci_detach", "pci_reattach",
-         "do_power_cycle"],
+         "do_power_cycle", "get_midplane_down_reason"],
     )
     def test_not_implemented_methods_raise(self, method_name):
         with pytest.raises(NotImplementedError):