On Tue, Dec 04, 2018 at 05:00:36PM +0100, Johan Hovold wrote:
The USB-serial console implementation has never reported the actual terminal settings used. Despite storing the corresponding cflags in its struct console, this was never honoured on later tty open() where the tty termios would be left initialised to the driver defaults.
Unlike the serial console implementation, the USB-serial code calls subdriver open() already at console setup. While calling set_termios() before open() looks like it could work for some USB-serial drivers, others definitely do not expect this, so modelling this after serial core is going to be intrusive, if at all possible.
Instead, use a (renamed) tty helper to save the termios data used at console setup, so that the tty termios reflects the actual terminal settings after a subsequent tty open().
Note that the calls to tty_init_termios() (tty_driver_install()) and tty_save_termios() are serialised using the disconnect mutex.
This specifically fixes a regression that was triggered by a recent change adding software flow control to the pl2303 driver: a getty trying to disable flow control while leaving the baud rate unchanged would now also set the baud rate to the driver default (prior to the flow-control change this had been a noop).
Fixes: 7041d9c3f01b ("USB: serial: pl2303: add support for tx xon/xoff flow control") Cc: stable stable@vger.kernel.org # 4.18 Reported-by: Jarkko Nikula jarkko.nikula@linux.intel.com Cc: Florian Zumbiehl florz@florz.de Signed-off-by: Johan Hovold johan@kernel.org
drivers/tty/tty_io.c | 11 +++++++++-- drivers/usb/serial/console.c | 2 +- include/linux/tty.h | 1 + 3 files changed, 11 insertions(+), 3 deletions(-)
Ah, messy :)
Want me to take this through my tty tree?
thanks,
greg k-h