Hi Kyösti,
On 11/03/2014 10:18 AM, Kyösti Mälkki wrote:
> There are applications where it is desirable to not hangup ttyGS* when
> USB disconnect is detected. USB host side of communication may
> power-cycle periodically or there may be the actual need to physically
> disconnect and reconnect USB cable temporarily.
>
> USB disconnects on serial gadget are comparable to loss of Carrier Detect
> of conventional UARTs. With the change, if ttyGS* has termios CLOCAL flag
> set, disconnect on USB does not hangup the TTY.
>
> Signed-off-by: Kyösti Mälkki <kyosti.malkki@xxxxxxxxx>
> ---
> drivers/usb/gadget/function/u_serial.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
> index 491082a..dabc165 100644
> --- a/drivers/usb/gadget/function/u_serial.c
> +++ b/drivers/usb/gadget/function/u_serial.c
> @@ -1253,9 +1253,16 @@ void gserial_disconnect(struct gserial *gser)
> port->port_usb = NULL;
> gser->ioport = NULL;
> if (port->port.count > 0 || port->openclose) {
> + struct tty_struct *tty;
> +
> wake_up_interruptible(&port->drain_wait);
> - if (port->port.tty)
> - tty_hangup(port->port.tty);
> + tty = port->port.tty;
> + if (tty) {
> + if (tty->termios.c_cflag & CLOCAL)
> + stop_tty(tty);
> + else
> + tty_hangup(tty);
It seems you missed my earlier email: what happens if you leave
out the stop_tty() call here?
I ask because the tty is still restartable from userspace after you
stop_tty() here. So if your goal is to prevent write() from
happening, this won't work.
Regards,
Peter Hurley
> + }
> }
> spin_unlock_irqrestore(&port->port_lock, flags);
>
>
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