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. Johan Changes in v2 - use assign_bit() in port-flag accessors (Jiri) - use const parameters in port-flag accessors (Jiri) - use kstrtobool() in attribute store (Andy, Greg) - fix "used" typo in commit messages (Andy) - use bool constant with port-flag accessor in ftdi quirk (Jiri) - add Mychaela's Reviewed-by tag to patch 3/7 - mention a few more example applications in the cover letter v1 - https://lore.kernel.org/r/20201130153742.9163-1-johan@xxxxxxxxxx Johan Hovold (5): tty: use assign_bit() in port-flag accessors tty: use const parameters in port-flag accessors tty: add port flag to suppress ready signalling on open serial: core: add sysfs attribute to suppress ready signalling on open USB: serial: add sysfs attribute to suppress ready signalling on open Mychaela N. Falconia (2): USB: serial: ftdi_sio: pass port to quirk port_probe functions USB: serial: ftdi_sio: add support for FreeCalypso DUART28C adapter Documentation/ABI/testing/sysfs-tty | 7 ++++ drivers/tty/serial/serial_core.c | 26 ++++++++++++++ drivers/tty/tty_port.c | 2 +- drivers/usb/serial/bus.c | 35 +++++++++++++++++-- drivers/usb/serial/ftdi_sio.c | 42 ++++++++++++++++++----- drivers/usb/serial/ftdi_sio_ids.h | 1 + include/linux/tty.h | 53 +++++++++++++---------------- 7 files changed, 125 insertions(+), 41 deletions(-) -- 2.26.2
