linux-kernel - Re: [PATCH v4 2/9] [media] v4l2-core: Add VFL_TYPE_TOUCH

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Date:	Wed, 22 Jun 2016 22:22:03 +0100
From:	Nick Dyer <nick.dyer@...ev.co.uk>
To:	Florian Echtler <floe@...terbrot.org>
Cc:	Hans Verkuil <hverkuil@...all.nl>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org,
	Benjamin Tissoires <benjamin.tissoires@...hat.com>,
	Benson Leung <bleung@...omium.org>,
	Alan Bowens <Alan.Bowens@...el.com>,
	Javier Martinez Canillas <javier@....samsung.com>,
	Chris Healy <cphealy@...il.com>,
	Henrik Rydberg <rydberg@...math.org>,
	Andrew Duggan <aduggan@...aptics.com>,
	James Chen <james.chen@....com.tw>,
	Dudley Du <dudl@...ress.com>,
	Andrew de los Reyes <adlr@...omium.org>,
	sheckylin@...omium.org, Peter Hutterer <peter.hutterer@...-t.net>,
	mchehab@....samsung.com
Subject: Re: [PATCH v4 2/9] [media] v4l2-core: Add VFL_TYPE_TOUCH_SENSOR

On 22/06/2016 21:38, Florian Echtler wrote:
> On Wed, 22 Jun 2016, Nick Dyer wrote:
> 
>> On 22/06/2016 12:48, Florian Echtler wrote:
>>> On 20.06.2016 14:00, Hans Verkuil wrote:
>>>> On 06/17/2016 04:16 PM, Nick Dyer wrote:
>>>>>
>>>>> Use a new device prefix v4l-touch for these devices, to stop generic
>>>>> capture software from treating them as webcams.
>>
>>> Come to think of it, wouldn't it make sense to expose the other touch
>>> devices as generic frame grabbers, too, so you can easily view the debug
>>> output with any generic tool like cheese?
>>
>> While I like the idea of being able to use the generic tools, I think we
>> needed to do something to stop these devices turning up in e.g. video
>> conferencing software - it would cause a lot of confusion. There's nothing
>> stopping particular tools adding the necessary code to handle touch devices
>> if they feel their users want it.
> 
> Just to clarify: from the userspace point-of-view, would this change simply
> modify the prefix of the device node (i.e. /dev/video1 -> /dev/v4l-touch1),
> or would it somehow affect the API? If it's just the device node name, then
> that shouldn't be a problem after all, because e.g. reacTIVision requires
> you to specify the exact camera to be used anyway.

With the changes that Hans Verkuil has asked me to do:
* The device node is /dev/v4l-touch0-255
* There are several new formats eg. V4L2_TCH_FMT_DELTA_TD16 (16 bit deltas)
* I've defined new types VFL_TYPE_TOUCH, V4L2_BUF_TYPE_TOUCH_CAPTURE,
V4L2_INPUT_TYPE_TOUCH

We're just testing the changes, I hope to post an updated version soon.