Hi Johan, Thank you for finally taking the time to address the issue at hand. Your generalized solution and your reimplementation of my DUART28C quirk using your new tty port flag would indeed solve my immediate problem of getting mainline Linux support for FreeCalypso DUART28C, so I would be perfectly happy if your new patch series gets mainlined. > I don't think we need to change the B0 handling. It will never be set > unless explicitly requested by the user. I originally thought that DTR & RTS assertion upon change from B0 to Bxxx had to be suppressed because I thought that the initial termios state of a completely cold ttyUSB port (created upon USB device plug-in but never opened) had B0 in it - but now I see that this cold initial state is B9600 rather than B0, so indeed you are right in that B0 can only be set by users and thus can be ignored for purposes of legacy-gunk-free custom hw like mine. > I'm adding a new tty port flag that can be used to suppress the > assertion of DTR/RTS to signal DTE readiness on open named NORDY. > Eventually we can expose it through termios to match HUPCL that controls > the behaviour on final close. For now I'm only adding a sysfs interface > but that also allows control over these signals on first open. I don't see how exposing this new flag via termios would be of any use (it's a chicken and egg problem: one needs to open the tty device in order to do termios ioctls on it, and if that initial open triggers DTR/RTS hardware actions, then the end user is still screwed), but making this flag accessible for setting and clearing via sysfs is a good idea. For hardware engineers like me who design and build their own boards with the USB-serial chip fully embedded and who have their own custom USB IDs, applying a driver quirk tied to that custom USB ID is still the best solution in terms of ultimate friendliness to the lowly end user of the finished hardware. But for users who don't have the luxury of a custom USB ID, i.e., users of a non-DTR-RTS-glitch-tolerant RS-232 device connected to a standard PC COM port or via a generic off-the-shelf USB to serial DE9M cable, being able to set the needed quirk via sysfs can be a life saver. > Your FTDI quirk now only needs to set this flag on probe to override the > default behaviour. The end result with respect to your device should be > the same except for B0, which is still handled as before. LGTM, Mychaela
