linux-kernel - Re: [PATCH 2/5] HID: hid-multitouch: get maxcontacts also from logical

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Message-ID: <CAN+gG=Fyq7S54rkDRsUmEytxcU-HQb68qENnED8=xaUxF3-BXQ@mail.gmail.com>
Date:	Thu, 10 May 2012 14:15:31 +0200
From:	Benjamin Tissoires <benjamin.tissoires@...il.com>
To:	Henrik Rydberg <rydberg@...omail.se>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Stephane Chatty <chatty@...c.fr>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] HID: hid-multitouch: get maxcontacts also from
 logical_max value

On Wed, May 9, 2012 at 9:46 PM, Henrik Rydberg <rydberg@...omail.se> wrote:
> Hi Benjamin,
>
>> >> Win8 devices are required to present the feature "Maximum Contact Number".
>> >> If the current value is 0, then, the driver can get the actual supported
>> >> contact count by seeing the logical_max.
>> >
>> > And for win7, it is zero?
>>
>> Well, the truth is that the Win8 specification formally describes the
>> values here. And to get the certification, hardware makers have to put
>> the right value in logical_max.
>> TBH, I don't care that much now with win7 devices. Most of them are a
>> piece of crap (not true dual fingers, problems in hid reports
>> descriptors, etc...), but they just work (we made the necessary
>> things). With the introduction of Win8, hardware makers will have to
>> *certify* their devices, and thus, the Win8 driver is much less
>> tolerant. I really think that we are going to see more and more win8
>> devices, whereas win7 devices will fade out.
>>
>> I had to add this patch because I have a win8 device that has the
>> value associated to this field at 0, and it's the first I saw with
>> this behavior.
>
> As long as all existing devices are unaffected, it's fine, hence the question.

I checked all the reports descriptors that I have.
2 devices (one Stantum and one Irtouch) present an unrealistic
logical_max value (255). The thing is that if this logical_max is
false, and if the value is not provided, then I don't know how could I
retrieve the right value beside introducing a MT_CLS...

Henrik, do you think that 255 is two much for the slots?

Thanks,
Benjamin

>
> Thanks,
> Henrik
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