On 10/27/2014 09:38 AM, Felipe Balbi wrote:
> Hi,
>
> On Sun, Oct 26, 2014 at 08:01:30PM +0200, 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 | 9 +++++++--
>> 1 file changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
>> index 491082a..e68ffd7 100644
>> --- a/drivers/usb/gadget/function/u_serial.c
>> +++ b/drivers/usb/gadget/function/u_serial.c
>> @@ -1254,8 +1254,13 @@ void gserial_disconnect(struct gserial *gser)
>> gser->ioport = NULL;
>> if (port->port.count > 0 || port->openclose) {
>> wake_up_interruptible(&port->drain_wait);
>> - if (port->port.tty)
>> - tty_hangup(port->port.tty);
>> + struct tty_struct *tty = port->port.tty;
>
> declare above as Sergei said.
>
>> + if (tty) {
>
> is there any situation where tty would be NULL here ?
>
>> + if (tty->termios.c_cflag & CLOCAL)
>> + stop_tty(tty);
>> + else
>> + tty_hangup(tty);
>
> this I'll defer to Greg who also maintains tty.
I'm curious what happens without stop_tty().
The tty is restartable from userspace with
tcflow(fd, TCOOFF);
tcflow(fd, TCOON);
Regards,
Peter Hurley
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