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

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Date:	Mon, 20 Sep 2010 21:43:37 +0200
From:	Stéphane Chatty <chatty@...c.fr>
To:	Henrik Rydberg <rydberg@...omail.se>
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


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?

Cheers,

St.

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