On Wed, Dec 02, 2020 at 12:39:35PM +0100, Johan Hovold wrote: > This series adds a new NORDY port flag to suppress raising the > modem-control lines on open to signal DTE readiness. > > This can be used to implement a NORDY termios control flag to complement > HUPCL, which controls lowering of the modem-control lines on final > close. > > Initially drivers can export the flag through sysfs, which also allows > control over the lines on first open. Such an interface is implemented > for serial core and USB serial. > > The motivation for this is to allow for applications where the DTR and > RTS lines are used for non-standard purposes (e.g. generating power-on > and reset pulses) to open the port without undesirable side effects. > > The final patches enables this flag by default for such a USB serial > device. > > Other examples include HAM-radio devices where DTR and RTS is used for > push-to-talk and continuous-wave control and various Arduino boards > which are reset on open unless a jumper is physically removed. > > Greg, are you ok we me taking this through my tree? I'm planning on some > follow ups to the ftdi driver and the tty/serial changes are fairly > self-contained. > > Also let me know if you prefer to hold this off for 5.12. The change is > minimal, self-contained and low-risk, but it is a new interface and late > in the release cycle as Andy pointed out. I took the first 2 patches now, that was easy :) I think we need more review for the rest of the series. This does change the way serial ports work in a non-traditional way (i.e. using sysfs instead of terminal settings). So I want to get a bunch of people to agree that this is ok to do things this way now before taking this new user-visible api. thanks, greg k-h
