[Mellanox] add PSU fan direction support (sonic-net#14508)

- Why I did it
Add PSU fan direction support

- How I did it
Implement fan.get_direction for PSU fan

- How to verify it
Manual test
Unit test

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

@@ -31,6 +31,7 @@
     from .led import ComponentFaultyIndicator
     from . import utils
     from .thermal import Thermal
+    from .fan_drawer import VirtualDrawer
 except ImportError as e:
     raise ImportError (str(e) + "- required module not found")
 
@@ -45,7 +46,10 @@
 FAN_DIR = "/var/run/hw-management/thermal/fan{}_dir"
 FAN_DIR_VALUE_EXHAUST = 0
 FAN_DIR_VALUE_INTAKE = 1
-
+FAN_DIR_MAPPING = {
+    FAN_DIR_VALUE_EXHAUST: FanBase.FAN_DIRECTION_EXHAUST,
+    FAN_DIR_VALUE_INTAKE: FanBase.FAN_DIRECTION_INTAKE,
+}
 
 class MlnxFan(FanBase):
     def __init__(self, fan_index, position):
@@ -125,6 +129,20 @@ def is_replaceable(self):
         """
         return False
 
+    @classmethod
+    def get_fan_direction(cls, dir_path):
+        try:
+            fan_dir = utils.read_int_from_file(dir_path, raise_exception=True)
+            ret = FAN_DIR_MAPPING.get(fan_dir)
+            if ret is None:
+                logger.log_error(f"Got wrong value {fan_dir} for fan direction {dir_path}")
+                return FanBase.FAN_DIRECTION_NOT_APPLICABLE
+            else:
+                return ret
+        except (ValueError, IOError) as e:
+            logger.log_error(f"Failed to read fan direction from {dir_path} - {e}")
+            return FanBase.FAN_DIRECTION_NOT_APPLICABLE
+
 
 class PsuFan(MlnxFan):
     # PSU fan speed vector
@@ -145,6 +163,7 @@ def __init__(self, fan_index, position, psu):
         self.psu_i2c_bus_path = os.path.join(CONFIG_PATH, 'psu{0}_i2c_bus'.format(self.index))
         self.psu_i2c_addr_path = os.path.join(CONFIG_PATH, 'psu{0}_i2c_addr'.format(self.index))
         self.psu_i2c_command_path = os.path.join(CONFIG_PATH, 'fan_command')
+        self.psu_fan_dir_path = os.path.join(FAN_PATH, "psu{}_fan_dir".format(self.index))
 
     def get_direction(self):
         """
@@ -165,7 +184,10 @@ def get_direction(self):
                 1 stands for forward, in other words intake
                 0 stands for reverse, in other words exhaust
         """
-        return self.FAN_DIRECTION_NOT_APPLICABLE
+        if not os.path.exists(self.psu_fan_dir_path) or not self.get_presence():
+            return self.FAN_DIRECTION_NOT_APPLICABLE
+
+        return MlnxFan.get_fan_direction(self.psu_fan_dir_path)
 
     def get_status(self):
         """
@@ -263,7 +285,10 @@ def get_direction(self):
                 1 stands for forward, in other words intake
                 0 stands for reverse, in other words exhaust
         """
-        return self.fan_drawer.get_direction()
+        if not isinstance(self.fan_drawer, VirtualDrawer):
+            return self.fan_drawer.get_direction()
+        else:
+            return MlnxFan.get_fan_direction(FAN_DIR.format(self.index))
 
     def get_status(self):
         """

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

@@ -58,19 +58,8 @@ def get_direction(self):
         if not self.get_presence():
             return FanBase.FAN_DIRECTION_NOT_APPLICABLE
 
-        try:
-            from .fan import FAN_DIR, FAN_DIR_VALUE_INTAKE, FAN_DIR_VALUE_EXHAUST
-            fan_dir = utils.read_int_from_file(FAN_DIR.format(self._index), raise_exception=True)
-            if fan_dir == FAN_DIR_VALUE_INTAKE:
-                return FanBase.FAN_DIRECTION_INTAKE
-            elif fan_dir == FAN_DIR_VALUE_EXHAUST:
-                return FanBase.FAN_DIRECTION_EXHAUST
-            else:
-                logger.log_error("Got wrong value {} for fan direction {}".format(fan_dir, self._index))
-                return FanBase.FAN_DIRECTION_NOT_APPLICABLE
-        except (ValueError, IOError) as e:
-            logger.log_error("Failed to read fan direction status to {}".format(repr(e)))
-            return FanBase.FAN_DIRECTION_NOT_APPLICABLE
+        from .fan import FAN_DIR, MlnxFan
+        return MlnxFan.get_fan_direction(FAN_DIR.format(self._index))
 
     def set_status_led(self, color):
         """

platform/mellanox/mlnx-platform-api/tests/test_fan_api.py

@@ -25,7 +25,7 @@
 sys.path.insert(0, modules_path)
 
 from sonic_platform import utils
-from sonic_platform.fan import Fan, PsuFan
+from sonic_platform.fan import Fan, PsuFan, FAN_DIR_VALUE_INTAKE, FAN_DIR_VALUE_EXHAUST
 from sonic_platform.fan_drawer import RealDrawer, VirtualDrawer
 from sonic_platform.psu import Psu
 
@@ -107,11 +107,12 @@ def test_system_fan_set_speed(self, mock_write_file):
         fan.set_speed(60)
         mock_write_file.assert_called_with(fan.fan_speed_set_path, 153, raise_exception=True)
 
+    @patch('sonic_platform.utils.read_int_from_file')
     @patch('sonic_platform.thermal.Thermal.get_cooling_level')
     @patch('sonic_platform.psu.Psu.get_presence')
     @patch('sonic_platform.psu.Psu.get_powergood_status')
     @patch('os.path.exists')
-    def test_psu_fan_basic(self, mock_path_exists, mock_powergood, mock_presence, mock_cooling_level):
+    def test_psu_fan_basic(self, mock_path_exists, mock_powergood, mock_presence, mock_cooling_level, mock_read_int):
         mock_path_exists.return_value = False
         psu = Psu(0)
         fan = PsuFan(0, 1, psu)
@@ -126,6 +127,12 @@ def test_psu_fan_basic(self, mock_path_exists, mock_powergood, mock_presence, mo
         assert fan.get_presence() is True
         mock_cooling_level.return_value = 7
         assert fan.get_target_speed() == 70
+        mock_read_int.return_value = FAN_DIR_VALUE_INTAKE
+        assert fan.get_direction() == Fan.FAN_DIRECTION_INTAKE
+        mock_read_int.return_value = FAN_DIR_VALUE_EXHAUST
+        assert fan.get_direction() == Fan.FAN_DIRECTION_EXHAUST
+        mock_read_int.return_value = -1 # invalid value
+        assert fan.get_direction() == Fan.FAN_DIRECTION_NOT_APPLICABLE
 
     def test_psu_fan_set_speed(self):
         psu = Psu(0)