On Tue, 17 Aug 2010, Daniel Mack wrote: > > I believe the DTR/RTS lines are both raised all the time on a regular serial > > port when hardware flow control isn't enabled. My guess is that the ftdi_sio > > driver probably sets them low when hardware flow control is disabled (or maybe > > just leaves them alone). I think the fix, therefore, may be that the ftdi_sio > > driver needs to force DTR/RTS both high when hardware flow control is disabled. > > I'm not convinced about this approach. The thing is that if your > hardware does not need hardware flow control, these lines shouldn't > matter at all. IOW, they should be left unconnected as the chip itself > won't care either. > > However, if you tell the chip that you _do_ need hardware flow, it will > not send out any data on TxD as long as CTS is not asserted. I disagree with Dave's suggestion. Both of you should keep in mind that even when the DTR/RTS lines aren't needed for hardware flow control, they might be needed for some other device-specific type of signalling. I guess it would be okay for the driver to raise them automatically when hardware flow control is disabled and when the port is first opened, but the driver certainly should _not_ force them on all the time, under any circumstances. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
