zskbd_ctrl
static void zskbd_ctrl(struct zs_chanstate *, uint8_t, uint8_t,
zskbd_ctrl(cs, ZSKBD_CTRL_A_RCB, 0, 0, 0);
zskbd_ctrl(cs, a_on, a_off, b_on, b_off);
zskbd_ctrl(cs, 0, ZSKBD_CTRL_A_NOCLICK, 0, 0);
zskbd_ctrl(cs, ZSKBD_CTRL_A_NOCLICK, 0, 0, 0);