CH341_BIT_DTR
priv->mcr |= CH341_BIT_RTS | CH341_BIT_DTR;
priv->mcr &= ~(CH341_BIT_RTS | CH341_BIT_DTR);
priv->mcr &= ~(CH341_BIT_DTR | CH341_BIT_RTS);
priv->mcr |= (CH341_BIT_DTR | CH341_BIT_RTS);
priv->mcr |= CH341_BIT_DTR;
priv->mcr &= ~CH341_BIT_DTR;
result = ((mcr & CH341_BIT_DTR) ? TIOCM_DTR : 0)