BT_C_H2B_ATN
v |= BT_C_CLR_WR_PTR | BT_C_CLR_RD_PTR | BT_C_B2H_ATN | BT_C_H2B_ATN;
if (bt_wait(sc, BT_C_B_BUSY | BT_C_H2B_ATN, 0) < 0) {
OUTB(sc, BT_CTRL_REG, BT_C_H2B_ATN);
if (bt_wait(sc, BT_C_B_BUSY | BT_C_H2B_ATN, 0) < 0) {