Re: [PATCHv2] serio: add hangup support

From: Hans Verkuil <hverkuil@xs4all.nl>
To: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: linux-input <linux-input@vger.kernel.org>,
	"linux-media@vger.kernel.org" <linux-media@vger.kernel.org>
Subject: Re: [PATCHv2] serio: add hangup support
Date: Thu, 4 Aug 2016 10:25:50 +0200	[thread overview]
Message-ID: <54e5a952-f37c-3777-e789-39a4d59e1923@xs4all.nl> (raw)
In-Reply-To: <20160803152602.GB29702@dtor-ws>

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.verkuil@cisco.com>
>> Tested-by: Hans Verkuil <hans.verkuil@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