关于xp100 usb scanner驱动(读写register)的疑惑

int readRegOut(usb_dev_handle *udev,
                         unsigned char reg, unsigned char *val, int out) {

  char command[4];
  int ret;

  command[0] = 1;
  command[1] = reg;
  command[2] = 0;
  command[3] = 1;

  ret = usb_bulk_write(udev, 0x03, command, 4, 500);
  if (ret < 0)
    return ret;

  ret = usb_bulk_read(udev, 0x02, val, 1, 1000);
  if (out)
    printf("r-- %02x [01]  :  %i (%02x)  :  %i\n", reg, (int)(*val),
           (int)(*val), ret);
  return ret;

      // readReg
}

这是visioneer xp100 usb scanner驱动的一段代码(读寄存器)
0x03为scanner USB bulk_out_endpoint地址
0x02为scanner USB bulk_in_endpoint地址
我的疑问是:

  command[0] = 1;
  command[1] = reg;
  command[2] = 0;
  command[3] = 1;

这种命令格式(写reg寄存器)是开发厂商定义的还是所有的usb设备都要这样写？

希望大家能帮帮我,谢谢！

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