adding msc Start Stop to buitin command, but not complate yet

add tud_msc_start_stop_cb() as optional callback

examples/device/cdc_msc_hid/src/msc_disk.c

@@ -152,6 +152,26 @@ void tud_msc_capacity_cb(uint8_t lun, uint32_t* block_count, uint16_t* block_siz
   *block_size  = DISK_BLOCK_SIZE;
 }
 
+// Invoked when received Start Stop Unit command
+// - Start = 0 : stopped power mode, if load_eject = 1 : unload disk storage
+// - Start = 1 : active mode, if load_eject = 1 : load disk storage
+void tud_msc_start_stop_cb(uint8_t lun, uint8_t power_condition, bool start, bool load_eject)
+{
+  (void) lun;
+  (void) power_condition;
+
+  if ( load_eject )
+  {
+    if (start)
+    {
+      // load disk storage
+    }else
+    {
+      // unload disk storage
+    }
+  }
+}
+
 // Callback invoked when received READ10 command.
 // Copy disk's data to buffer (up to bufsize) and return number of copied bytes.
 int32_t tud_msc_read10_cb(uint8_t lun, uint32_t lba, uint32_t offset, void* buffer, uint32_t bufsize)
@@ -200,18 +220,6 @@ int32_t tud_msc_scsi_cb (uint8_t lun, uint8_t const scsi_cmd[16], void* buffer,
       resplen = 0;
     break;
 
-    case SCSI_CMD_START_STOP_UNIT:
-      // Host try to eject/safe remove/poweroff us. We could safely disconnect with disk storage, or go into lower power
-      /* scsi_start_stop_unit_t const * start_stop = (scsi_start_stop_unit_t const *) scsi_cmd;
-        // Start bit = 0 : low power mode, if load_eject = 1 : unmount disk storage as well
-        // Start bit = 1 : Ready mode, if load_eject = 1 : mount disk storage
-        start_stop->start;
-        start_stop->load_eject;
-       */
-       resplen = 0;
-    break;
-
-
     default:
       // Set Sense = Invalid Command Operation
       tud_msc_set_sense(lun, SCSI_SENSE_ILLEGAL_REQUEST, 0x20, 0x00);