[barefoot][platform] Refactor chassis.py (#7704)

#### Why I did it
On our platforms syncd must be up while using the sonic_platform.
The issue is warm-reboot script first disables syncd then instantiate Chassis, which tries to connect syncd in __init__.

#### How I did it
Refactor Chassis to lazy initialize components.

Signed-off-by: Volodymyr Boyko <volodymyrx.boiko@intel.com>

platform/barefoot/sonic-platform-modules-bfn-montara/sonic_platform/chassis.py

@@ -3,8 +3,8 @@
 try:
     import sys
     from sonic_platform_base.chassis_base import ChassisBase
-    from sonic_platform.sfp import Sfp
-    from sonic_platform.psu import Psu
+    from sonic_platform.sfp import Sfp, sfp_list_get
+    from sonic_platform.psu import psu_list_get
     from sonic_platform.fan_drawer import fan_drawer_list_get
     from sonic_platform.thermal import thermal_list_get
     from eeprom import Eeprom
@@ -18,18 +18,21 @@ class Chassis(ChassisBase):
     def __init__(self):
         ChassisBase.__init__(self)
 
-        self._eeprom = Eeprom()
-
-        for index in range(Sfp.port_start(), Sfp.port_end() + 1):
-            sfp_node = Sfp(index)
-            self._sfp_list.append(sfp_node)
-
-        for i in range(1, Psu.get_num_psus() + 1):
-            psu = Psu(i)
-            self._psu_list.append(psu)
-
+        self.__eeprom = None
         self.__fan_drawers = None
         self.__thermals = None
+        self.__psu_list = None
+        self.__sfp_list = None
+
+    @property
+    def _eeprom(self):
+        if self.__eeprom is None:
+            self.__eeprom = Eeprom()
+        return self.__eeprom
+
+    @_eeprom.setter
+    def _eeprom(self, value):
+        pass
 
     @property
     def _fan_drawer_list(self):
@@ -51,6 +54,26 @@ class Chassis(ChassisBase):
     def _thermal_list(self, value):
         pass
 
+    @property
+    def _psu_list(self):
+        if self.__psu_list is None:
+            self.__psu_list = psu_list_get()
+        return self.__psu_list
+
+    @_psu_list.setter
+    def _psu_list(self, value):
+        pass
+
+    @property
+    def _sfp_list(self):
+        if self.__sfp_list is None:
+            self.__sfp_list = sfp_list_get()
+        return self.__sfp_list
+
+    @_sfp_list.setter
+    def _sfp_list(self, value):
+        pass
+
     def get_name(self):
         """
         Retrieves the name of the chassis

platform/barefoot/sonic-platform-modules-bfn-montara/sonic_platform/psu.py

@@ -104,3 +104,10 @@ class Psu(PsuBase):
 
     def is_replaceable(self):
         return True
+
+def psu_list_get():
+    psu_list = []
+    for i in range(1, Psu.get_num_psus() + 1):
+        psu = Psu(i)
+        psu_list.append(psu)
+    return psu_list

platform/barefoot/sonic-platform-modules-bfn-montara/sonic_platform/sfp.py

@@ -269,3 +269,10 @@ class Sfp(SfpBase):
 
     def get_change_event(self, timeout=0):
         return Sfp.get_transceiver_change_event(timeout)
+
+def sfp_list_get():
+    sfp_list = []
+    for index in range(Sfp.port_start(), Sfp.port_end() + 1):
+        sfp_node = Sfp(index)
+        sfp_list.append(sfp_node)
+    return sfp_list