[Mellanox] PSU led platform API fixes (#6214)

- Why I did it
Fix setting PSU led to 'green' or 'red' states.
Fix return False if unsupported color request.
Remove 'off' option for PSU led API since it is not supported in Mellanox.

- How I did it
Fix import missing information.
Return 'False' when unsupported led color is requested, preventing an exception.

- How to verify it
Try to set PSU LED to different status with Mellanox platform device.
Try to set PSU LED color to unsupported color with Mellanox platform device.

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

@@ -1,4 +1,8 @@
 class Led(object):
+    LED_PATH = "/var/run/hw-management/led/"
+    LED_ON = '1'
+    LED_OFF = '0'
+    LED_BLINK = '50'
     STATUS_LED_COLOR_GREEN = 'green'
     STATUS_LED_COLOR_GREEN_BLINK = 'green_blink'
     STATUS_LED_COLOR_RED = 'red'
@@ -24,9 +28,11 @@ def add_virtual_leds(self, led):
     def update_status_led(self):
         target_color = Led.STATUS_LED_COLOR_GREEN
         for virtual_led in self._virtual_leds:
-            if SharedLed.LED_PRIORITY[virtual_led.get_led_color()] < SharedLed.LED_PRIORITY[target_color]:
-                target_color = virtual_led.get_led_color()
-
+            try:
+                if SharedLed.LED_PRIORITY[virtual_led.get_led_color()] < SharedLed.LED_PRIORITY[target_color]:
+                    target_color = virtual_led.get_led_color()
+            except KeyError:
+                return False
         self._target_color = target_color
         return True
 
@@ -41,8 +47,13 @@ def __init__(self, shared_led):
         self._shared_led.add_virtual_leds(self)
 
     def set_status(self, color):
+        current_color = self._color
         self._color = color
-        return self._shared_led.update_status_led()
+        if self._shared_led.update_status_led():
+            return True
+        else:
+            self._color = current_color
+            return False
 
     def get_led_color(self):
         return self._color

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

@@ -13,6 +13,7 @@
     from sonic_platform_base.psu_base import PsuBase
     from sonic_py_common.logger import Logger
     from sonic_platform.fan import Fan
+    from sonic_platform.led import Led
 except ImportError as e:
     raise ImportError (str(e) + "- required module not found")
 
@@ -188,7 +189,7 @@ def get_power(self):
     def _get_led_capability(self):
         cap_list = None
         try:
-            with open(os.path.join(LED_PATH, self.psu_led_cap_path), 'r') as psu_led_cap:
+            with open(os.path.join(Led.LED_PATH, self.psu_led_cap_path), 'r') as psu_led_cap:
                     caps = psu_led_cap.read()
                     cap_list = caps.split()
         except (ValueError, IOError):
@@ -217,33 +218,21 @@ def set_status_led(self, color):
 
         status = False
         try:
-            if color == self.STATUS_LED_COLOR_GREEN:
-                with open(os.path.join(LED_PATH, self.psu_green_led_path), 'w') as psu_led:
-                    psu_led.write(LED_ON)
+            if color == Led.STATUS_LED_COLOR_GREEN:
+                with open(os.path.join(Led.LED_PATH, self.psu_green_led_path), 'w') as psu_led:
+                    psu_led.write(Led.LED_ON)
                     status = True
-            elif color == self.STATUS_LED_COLOR_RED:
+            elif color == Led.STATUS_LED_COLOR_RED:
                 # Some fan don't support red led but support orange led, in this case we set led to orange
-                if self.STATUS_LED_COLOR_RED in led_cap_list:
-                    led_path = os.path.join(LED_PATH, self.psu_red_led_path)
-                elif self.STATUS_LED_COLOR_ORANGE in led_cap_list:
-                    led_path = os.path.join(LED_PATH, self.psu_orange_led_path)
+                if Led.STATUS_LED_COLOR_RED in led_cap_list:
+                    led_path = os.path.join(Led.LED_PATH, self.psu_red_led_path)
+                elif Led.STATUS_LED_COLOR_ORANGE in led_cap_list:
+                    led_path = os.path.join(Led.LED_PATH, self.psu_orange_led_path)
                 else:
                     return False
                 with open(led_path, 'w') as psu_led:
-                    psu_led.write(LED_ON)
+                    psu_led.write(Led.LED_ON)
                     status = True
-            elif color == self.STATUS_LED_COLOR_OFF:
-                if self.STATUS_LED_COLOR_GREEN in led_cap_list:
-                    with open(os.path.join(LED_PATH, self.psu_green_led_path), 'w') as psu_led:
-                        psu_led.write(str(LED_OFF))
-                if self.STATUS_LED_COLOR_RED in led_cap_list:
-                    with open(os.path.join(LED_PATH, self.psu_red_led_path), 'w') as psu_led:
-                        psu_led.write(str(LED_OFF))
-                if self.STATUS_LED_COLOR_ORANGE in led_cap_list:
-                    with open(os.path.join(LED_PATH, self.psu_orange_led_path), 'w') as psu_led:
-                        psu_led.write(str(LED_OFF))
-
-                status = True
             else:
                 status = False
         except (ValueError, IOError):
@@ -261,24 +250,24 @@ def get_status_led(self):
         """
         led_cap_list = self._get_led_capability()
         if led_cap_list is None:
-            return self.STATUS_LED_COLOR_OFF
+            return Led.STATUS_LED_COLOR_OFF
 
         try:
-            with open(os.path.join(LED_PATH, self.psu_green_led_path), 'r') as psu_led:
-                if LED_OFF != psu_led.read().rstrip('\n'):
-                    return self.STATUS_LED_COLOR_GREEN
-            if self.STATUS_LED_COLOR_RED in led_cap_list:
-                with open(os.path.join(LED_PATH, self.psu_red_led_path), 'r') as psu_led:
-                    if LED_OFF != psu_led.read().rstrip('\n'):
-                        return self.STATUS_LED_COLOR_RED
-            if self.STATUS_LED_COLOR_ORANGE in led_cap_list:
-                with open(os.path.join(LED_PATH, self.psu_orange_led_path), 'r') as psu_led:
-                    if LED_OFF != psu_led.read().rstrip('\n'):
-                        return self.STATUS_LED_COLOR_RED
+            with open(os.path.join(Led.LED_PATH, self.psu_green_led_path), 'r') as psu_led:
+                if Led.LED_OFF != psu_led.read().rstrip('\n'):
+                    return Led.STATUS_LED_COLOR_GREEN
+            if Led.STATUS_LED_COLOR_RED in led_cap_list:
+                with open(os.path.join(Led.LED_PATH, self.psu_red_led_path), 'r') as psu_led:
+                    if Led.LED_OFF != psu_led.read().rstrip('\n'):
+                        return Led.STATUS_LED_COLOR_RED
+            if Led.STATUS_LED_COLOR_ORANGE in led_cap_list:
+                with open(os.path.join(Led.LED_PATH, self.psu_orange_led_path), 'r') as psu_led:
+                    if Led.LED_OFF != psu_led.read().rstrip('\n'):
+                        return Led.STATUS_LED_COLOR_RED
         except (ValueError, IOError) as e:
             raise RuntimeError("Failed to read led status for psu due to {}".format(repr(e)))
 
-        return self.STATUS_LED_COLOR_OFF
+        return Led.STATUS_LED_COLOR_OFF
 
 
     def get_power_available_status(self):