linux-kernel - Re: Linux USB HID should ignore values outside Logical Minimum/Maximum range

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Message-ID: <20111024203204.GA31721@core.coreip.homeip.net>
Date:	Mon, 24 Oct 2011 13:32:04 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Christoph Fritz <chf.fritz@...glemail.com>
Cc:	Denilson Figueiredo de Sá 
	<denilsonsa@...il.com>, linux-kernel@...r.kernel.org,
	Jiri Kosina <jkosina@...e.cz>, linux-input@...r.kernel.org,
	linux-usb@...r.kernel.org
Subject: Re: Linux USB HID should ignore values outside Logical
 Minimum/Maximum range

Hi Christoph,

On Mon, Oct 24, 2011 at 07:09:43PM +0200, Christoph Fritz wrote:
> Hi Denilson,
> 
>  please see my comment below.
> 
> On Sat, 2011-10-22 at 09:42 -0200, Denilson Figueiredo de Sá wrote:
> > Short description:
> > 
> > An absolute pointing device using USB HID defines a LOGICAL_MINIMUM and
> > a LOGICAL_MAXIMUM for X, Y axes, and then sends a HID report containing
> > values outside that range.
> > 
> > Linux kernel should ignore values outside that range, as they are not
> > meaningful.
> 
> To answer with a quote from the comment above input.h:"struct
> input_absinfo":
> 
>  *
>  * Note that input core does not clamp reported values to the
>  * [minimum, maximum] limits, such task is left to userspace.
>  *
> 
> to do so, use this from input.h:
> 
> #define EVIOCGABS(abs)		_IOR('E', 0x40 + (abs), struct input_absinfo)	/* get abs value/limits */
> #define EVIOCSABS(abs)		_IOW('E', 0xc0 + (abs), struct input_absinfo)	/* set abs value/limits */

While input core does not clam or validate the values reported by the
driver it might make sense to do so in hid-input; I am not sure how
often these limits programmed intorrectly. Jiri i sprobably the best
person to answer this question.

Thanks.

-- 
Dmitry
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