ISR_TX_EMPTY
err = vx_wait_isr_bit(chip, ISR_TX_EMPTY);
if (vx_wait_isr_bit(chip, ISR_TX_EMPTY) < 0) {
if (vx_wait_isr_bit(chip, ISR_TX_EMPTY) < 0) {
err = vx_wait_isr_bit(chip, ISR_TX_EMPTY);
if (vx_wait_isr_bit(_chip, ISR_TX_EMPTY) < 0)