AE_FLAG_TXAVAIL
if ((sc->ae_flags & AE_FLAG_TXAVAIL) == 0 ||
sc->ae_flags &= ~AE_FLAG_TXAVAIL;
sc->ae_flags &= ~AE_FLAG_TXAVAIL;
sc->ae_flags |= AE_FLAG_TXAVAIL;
if (sc->ae_flags & AE_FLAG_TXAVAIL) {
sc->ae_flags |= AE_FLAG_TXAVAIL; /* Free Tx's available. */