linux-kernel - Re: [PATCH 2/3] hid: 3m: Convert to MT slots

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Date:	Mon, 20 Sep 2010 22:04:57 +0200
From:	Henrik Rydberg <rydberg@...omail.se>
To:	Stéphane Chatty <chatty@...c.fr>
CC:	Jiri Kosina <jkosina@...e.cz>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] hid: 3m: Convert to MT slots

On 09/20/2010 10:01 PM, Stéphane Chatty wrote:

> 
> Le 20 sept. 10 à 21:51, Henrik Rydberg a écrit :
> 
>> On 09/20/2010 09:46 PM, Stéphane Chatty wrote:
>>
>>>
>>> Le 28 août 10 à 16:29, Henrik Rydberg a écrit :
>>>
>>>>  #define MAX_SLOTS        60
>>>> -#define MAX_TRKID        59
>>>> +#define MAX_TRKID        USHRT_MAX
>>>>
>>>
>>> Oops, I forgot this one: in the rest of the code, it seems to me that you use
>>> your knowledge that TRACKINGID cannot be more than 59 (you use it to map the
>>> tracking ID onto the slot ID). Therefore, why change TRKID to a larger value?
>>
>>
>> There are only 60 slots available, but an infinite number of tracking ids.
>> Nowhere is the tracking id assumed to be bounded by anything but MAX_TRKID.
>>
> 
> What about this:
> +            value = clamp_val(value, 0, MAX_SLOTS - 1);
>              if (md->valid) {
>                  md->curid = value;
>                  md->f[value].touch = md->touch;
> 
> If you had tracking IDs 59, 60 and 61 in the same frame, this would not work
> properly would it?


That is the slot id being set. The microtouch controller is also using slots
internally.

Henrik

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