Message-ID: <4C77AA45.4030805@euromail.se>
Date: Fri, 27 Aug 2010 14:06:29 +0200
From: Henrik Rydberg <rydberg@euromail.se>
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To: Rafi Rubin <rafi@seas.upenn.edu>
CC: jkosina@suse.cz, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org,
        dmitry.torokhov@gmail.com, chatty@enac.fr, micki@n-trig.com
Subject: Re: [PATCH 1/4] Adding documention
References: <1282798497-19791-1-git-send-email-rafi@seas.upenn.edu> <1282798497-19791-2-git-send-email-rafi@seas.upenn.edu>
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On 08/26/2010 06:54 AM, Rafi Rubin wrote:

[...]

> +Parameters

> +----------
> +
> +Note: values set at load time are global and will apply to all applicable
> +devices.  Adjusting parameters with sysfs will override the load time values,
> +but only for that one device.
> +
> +The following parameters are used to configure filters to reduce noise:
> +
> +activate_slack		number of fingers to ignore before processing events
> +
> +activation_height	size threshold to activate immediately
> +activation_width
> +
> +min_height		size threshold bellow which fingers are ignored
> +min_width		both to decide activation and during activity
> +
> +deactivate_slack	the number of "no contact" frames to ignore before
> +			propagating the end of activity events
> +
> +When the last finger is removed from the device, it sends a number of empty
> +frames.  By holding off on deactivation for a few frames we can tolerate false
> +erroneous disconnects, where the sensor may mistakenly not detect a finger that
> +is still present.  Thus deactivate_slack addresses problems where a users might
> +see breaks in lines during drawing, or drop an object during a long drag.


Without contact tracking, it is hard to imagine activation filtering to work
properly. I would advocate to remove this functionality from the driver, and add
it in userspace instead.

Henrik
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