On 07/15/2016 06:31 PM, Dmitry Torokhov wrote:
> Hi Hans,
>
> On Fri, Jul 15, 2016 at 01:27:21PM +0200, Hans Verkuil wrote:
>> For the upcoming 4.8 kernel I made a driver for the Pulse-Eight USB CEC
>> adapter.
>> This is a usb device that shows up as a ttyACM0 device. It requires that you
>> run
>> inputattach in order to communicate with it via serio.
>>
>> This all works well, but it would be nice to have a udev rule to
>> automatically
>> start inputattach. That too works OK, but the problem comes when the USB
>> device
>> is unplugged: the tty hangup is never handled by the serio framework so the
>> inputattach utility never exits and you have to kill it manually.
>>
>> By adding this hangup callback the inputattach utility now exists as soon as
>> I
>> unplug the USB device.
>>
>> Is this the correct approach?
>>
>> BTW, the new driver is found here:
>>
>> https://git.linuxtv.org/media_tree.git/tree/drivers/staging/media/pulse8-cec
>>
>> Regards,
>>
>> Hans
>>
>> Signed-off-by: Hans Verkuil <hans.verk...@cisco.com>
>>
>> ---
>> diff --git a/drivers/input/serio/serport.c b/drivers/input/serio/serport.c
>> index 9c927d3..a615846 100644
>> --- a/drivers/input/serio/serport.c
>> +++ b/drivers/input/serio/serport.c
>> @@ -248,6 +248,14 @@ static long serport_ldisc_compat_ioctl(struct
>> tty_struct *tty,
>> }
>> #endif
>>
>> +static int serport_ldisc_hangup(struct tty_struct * tty)
>> +{
>> + struct serport *serport = (struct serport *) tty->disc_data;
>> +
>> + serport_serio_close(serport->serio);
>
> I see what you mean, but this is not quite correct. I think we should
> make serport_serio_close() only reset the SERPORT_ACTIVE flag and have
> serport_ldisc_hangup() actually do:
>
> spin_lock_irqsave(&serport->lock, flags);
> set_bit(SERPORT_DEAD, &serport->flags);
> spin_unlock_irqrestore(&serport->lock, flags);
>
> wake_up_interruptible(&serport->wait);
I'm preparing a v2 of this patch, but I wonder if in this hangup code
I also need to clear the SERPORT_ACTIVE flag. Or is it guaranteed that
close() always precedes hangup()? In which case close() always clears that
flag.
Regards,
Hans
>
> i.e. if user (via device-driver - input core - evdev - userspace chain)
> stops using serio port we should not kill inputattach instance right
> then and there, but wait for the serial port device disconnect or
> something else killing inputattach.
>
> Vojtech, do you recall any of this code?
>
> Thanks.
>
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