On 08/03/2016 05:26 PM, Dmitry Torokhov wrote:
> 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.verk...@cisco.com>
>> Tested-by: Hans Verkuil <hans.verk...@cisco.com>
>> ---
>> 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.
OK, I wasn't sure about that myself, thanks for looking into this and taking
care of it.
Regards,
Hans
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