GPIOCSR
reg = rt2x00mmio_register_read(rt2x00dev, GPIOCSR);
rt2x00mmio_register_write(rt2x00dev, GPIOCSR, reg);
reg = rt2x00mmio_register_read(rt2x00dev, GPIOCSR);
reg = rt2x00mmio_register_read(rt2x00dev, GPIOCSR);
rt2x00mmio_register_write(rt2x00dev, GPIOCSR, reg);
reg = rt2x00mmio_register_read(rt2x00dev, GPIOCSR);
rt2x00mmio_register_write(rt2x00dev, GPIOCSR, 0x0000ff00);