PS2_CTRL_AUX_LOOPBACK
res = ps2_command(PS2_CTRL_AUX_LOOPBACK, &out, 1, &in, 1);
res = ps2_command(PS2_CTRL_AUX_LOOPBACK, &out, 1, &in, 1);
res = ps2_command(PS2_CTRL_AUX_LOOPBACK, &out, 1, &in, 1);
ps2_write_ctrl(PS2_CTRL_AUX_LOOPBACK);