AIFSN_CSR
reg = rt2x00mmio_register_read(rt2x00dev, AIFSN_CSR);
rt2x00mmio_register_write(rt2x00dev, AIFSN_CSR, reg);
reg = rt2x00usb_register_read(rt2x00dev, AIFSN_CSR);
rt2x00usb_register_write(rt2x00dev, AIFSN_CSR, reg);