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

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Message-ID: <4C97BAA2.6000309@euromail.se>
Date:	Mon, 20 Sep 2010 21:48:50 +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 09:43 PM, Stéphane Chatty wrote:

> 
> Le 28 août 10 à 16:29, Henrik Rydberg a écrit :
> 
>> The Microtouch controller is capable of doing finger tracking on
>> up to 60 fingers. To reduce bandwidth and cpu usage, convert the
>> driver to use the MT slots protocol.
> 
> As I understand it, this patch actually has three roles:
>  1. improving the evdev parameters of the device
>  2. cleaning the protocol to get rid of useless MISC/SCANCODE messages
>  3. convert the protocol to MT slots
> 
> 
>> +#define SN_MOVE            2048
>> +#define SN_WIDTH        128
>>
> 
> In the long run, it might be useful to comment these signal/noise constants
> 
> 
> 
>>              hid_map_usage(hi, usage, bit, max, EV_KEY, BTN_TOUCH);
>> +            input_set_capability(hi->input, EV_KEY, BTN_TOUCH);
> 
>>  {
>> +    /* tell hid-input to skip setup of these event types */
>>      if (usage->type == EV_KEY || usage->type == EV_ABS)
>> -        clear_bit(usage->code, *bit);
>> -
>> -    return 0;
>> +        set_bit(usage->type, hi->input->evbit);
>> +    return -1;
>>  }
>>
> 
> I understand this as a trick to get rid of MISC/SCANCODEs that are added for
> every EV_KEY message, consequence of a rule in hid-input.c. Wouldn't it be
> simpler to improve the rule than to work around it?


The main reason is to be able to set the fuzz parameters, which are otherwise
overwritten by hid-input setup.

Henrik
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