[device/as5835-54t] Implement get_transceiver_change_event() in sfputil.py (#3485)

Signed-off-by: brandon_chuang <brandon_chuang@edge-core.com>

device/accton/x86_64-accton_as5835_54t-r0/plugins/sfputil.py

@@ -11,6 +11,8 @@ try:
 except ImportError as e:
     raise ImportError("%s - required module not found" % str(e))
 
+SFP_STATUS_INSERTED = '1'
+SFP_STATUS_REMOVED = '0'
 
 class SfpUtil(SfpUtilBase):
     """Platform-specific SfpUtil class"""
@@ -216,10 +218,90 @@ class SfpUtil(SfpUtilBase):
         
         return True
 
-    def get_transceiver_change_event(self):
-        """
-        TODO: This function need to be implemented
-        when decide to support monitoring SFP(Xcvrd)
-        on this platform.
-        """
-        raise NotImplementedError
+    @property
+    def _get_presence_bitmap(self):
+
+        bitmap = ""
+        try:
+            reg_file = open("/sys/bus/i2c/devices/3-0062/module_present_all")
+        except IOError as e:
+            print "Error: unable to open file: %s" % str(e)
+            return False
+        bitmap += reg_file.readline().rstrip() + " "
+        reg_file.close()
+
+        rev = bitmap.split(" ")
+        rev.pop() # Remove the last useless character
+
+        # Save port 49-54 into buffer
+        tmp = rev.pop()
+
+        # Insert port 1-48
+        for i in range (0, 6):
+            rev.append(hex(0)[2:])
+            rev[i] = rev[i].zfill(2)
+
+        # Expand port 49-54
+        for i in range (0, 6):
+            val = (int(tmp,16) >> i) & 0x1
+            rev.append(hex(val)[2:])
+
+        rev = "".join(rev[::-1])
+        return int(rev,16)
+
+    data = {'valid':0, 'present':0} 
+    def get_transceiver_change_event(self, timeout=0):
+
+        start_time = time.time()
+        port_dict = {}
+        port = 0
+        blocking = False
+
+        if timeout == 0:
+            blocking = True
+        elif timeout > 0:
+            timeout = timeout / float(1000) # Convert to secs
+        else:
+            print "get_transceiver_change_event:Invalid timeout value", timeout
+            return False, {}
+
+        end_time = start_time + timeout
+        if start_time > end_time:
+            print 'get_transceiver_change_event:' \
+                       'time wrap / invalid timeout value', timeout
+
+            return False, {} # Time wrap or possibly incorrect timeout
+
+        while timeout >= 0:
+            # Check for OIR events and return updated port_dict
+
+            reg_value = self._get_presence_bitmap
+            changed_ports = self.data['present'] ^ reg_value
+            if changed_ports:
+                for port in range (self.port_start, self.port_end+1):
+                    # Mask off the bit corresponding to our port
+                    mask = (1 << (port - 1))
+                    if changed_ports & mask:
+
+                        if (reg_value & mask) == 0:
+                            port_dict[port] = SFP_STATUS_REMOVED
+                        else:
+                            port_dict[port] = SFP_STATUS_INSERTED
+
+                # Update cache 
+                self.data['present'] = reg_value
+                self.data['valid'] = 1
+                return True, port_dict
+
+            if blocking:
+                time.sleep(1)
+            else:
+                timeout = end_time - time.time()
+                if timeout >= 1:
+                    time.sleep(1) # We poll at 1 second granularity
+                else:
+                    if timeout > 0:
+                        time.sleep(timeout)
+                    return True, {}
+        print "get_transceiver_change_event: Should not reach here."
+        return False, {}