On Wed, Aug 03, 2016 at 01:00:44PM +0200, Hans Verkuil wrote:
> The Pulse-Eight USB CEC adapter 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 properly exits as
> soon as the USB device is unplugged.
>
> The udev rule I used on my Debian sid system is:
>
> SUBSYSTEM=="tty", KERNEL=="ttyACM[0-9]*", ATTRS{idVendor}=="2548", ATTRS{idProduct}=="1002", ACTION=="add", TAG+="systemd", ENV{SYSTEMD_WANTS}+="pulse8-cec-inputattach@%k.service"
>
> And pulse8-cec-inputattach@%k.service is as follows:
>
> ===============================================================
> [Unit]
> Description=inputattach for pulse8-cec device on %I
>
> [Service]
> Type=simple
> ExecStart=/usr/local/bin/inputattach --pulse8-cec /dev/%I
> KillMode=process
> ===============================================================
>
> Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> Tested-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> ---
> Change since the original RFC patch: don't call close() from the hangup() function,
> instead only set the DEAD flag in hangup() instead of in close().
> ---
> diff --git a/drivers/input/serio/serport.c b/drivers/input/serio/serport.c
> index 9c927d3..4045e95 100644
> --- a/drivers/input/serio/serport.c
> +++ b/drivers/input/serio/serport.c
> @@ -71,7 +71,6 @@ static void serport_serio_close(struct serio *serio)
>
> spin_lock_irqsave(&serport->lock, flags);
> clear_bit(SERPORT_ACTIVE, &serport->flags);
> - set_bit(SERPORT_DEAD, &serport->flags);
> spin_unlock_irqrestore(&serport->lock, flags);
>
> wake_up_interruptible(&serport->wait);
I think we should remove this line as well - the waiter is waiting on
SERPORT_DEAD bit, if we are not setting it we do not need to wake up the
waiter either.
I can fix it up on my side.
> @@ -248,6 +247,19 @@ 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;
> + unsigned long flags;
> +
> + spin_lock_irqsave(&serport->lock, flags);
> + set_bit(SERPORT_DEAD, &serport->flags);
> + spin_unlock_irqrestore(&serport->lock, flags);
> +
> + wake_up_interruptible(&serport->wait);
> + return 0;
> +}
> +
> static void serport_ldisc_write_wakeup(struct tty_struct * tty)
> {
> struct serport *serport = (struct serport *) tty->disc_data;
> @@ -274,6 +286,7 @@ static struct tty_ldisc_ops serport_ldisc = {
> .compat_ioctl = serport_ldisc_compat_ioctl,
> #endif
> .receive_buf = serport_ldisc_receive,
> + .hangup = serport_ldisc_hangup,
> .write_wakeup = serport_ldisc_write_wakeup
> };
>
Thanks.
--
Dmitry
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