linux-kernel - Re: [PATCH 1/4] hid-multitouch: Auto detection of maxcontacts

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Date:	Wed, 9 Mar 2011 10:03:45 +0100
From:	Benjamin Tissoires <benjamin.tissoires@...c.fr>
To:	Henrik Rydberg <rydberg@...omail.se>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Stephane Chatty <chatty@...-enac.fr>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] hid-multitouch: Auto detection of maxcontacts

On Wed, Mar 9, 2011 at 09:42, Henrik Rydberg <rydberg@...omail.se> wrote:
> Hi Benjamin,
>
>> This patch enables support of autodetection of maxcontacts.
>> We can still manually provide maxcontact in case the device
>> lies on it.
>>
>> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...c.fr>
>
> It seems quite alright to let the classes contain the expected number
> of contacts, so I do not really see the reason for that part of the
> patch. How about keeping the maxcontacts in the class, and then do
> max(hid-provided-maxcontacts, default-maxcontacts)?
>

Yep, I've got three particular reasons:
- 3M: there are two devices now, 1968 and 2256. The first one is a 10
touches only, whereas the second one is a 60 touches.
- autodetection of multitouch devices. I have some patches on my tree
(that we do not want to go upstream right now for some reasons) that
allows us to plug any unknown multitouch devices and to let
hid-multitouch handling it. As most of the devices are 2 touches only,
and as the generic way to work with a multitouch devices is to iterate
over all the slots, using 10 touches by default infers a lot of
instructions that can be avoided.
- finally, it simplifies the writing of the new CLS (we just need to
know how the device works to add the right quirks).

Cheers,
Benjamin
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