linux-kernel - Re: [PATCH v3 4/4] input: alps: Fix trackstick detection

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Message-Id: <201411141222.35319@pali>
Date:	Fri, 14 Nov 2014 12:22:33 +0100
From:	Pali Rohár <pali.rohar@...il.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Hans de Goede <hdegoede@...hat.com>,
	Yunkang Tang <yunkang.tang@...alps.com>,
	Tommy Will <tommywill2011@...il.com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/4] input: alps: Fix trackstick detection

On Sunday 09 November 2014 12:30:03 Pali Rohár wrote:
> On Sunday 09 November 2014 09:05:04 Dmitry Torokhov wrote:
> > Hi Pali,
> > 
> > On Sun, Nov 02, 2014 at 12:25:10AM +0100, Pali Rohár wrote:
> > >  int alps_detect(struct psmouse *psmouse, bool
> > >  set_properties) {
> > > 
> > > -	struct alps_data dummy;
> > > +	unsigned char e6[4];
> > > 
> > > -	if (alps_identify(psmouse, &dummy) < 0)
> > > -		return -1;
> > > +	/*
> > > +	 * Try "E6 report".
> > > +	 * ALPS should return 0,0,10 or 0,0,100 if no buttons
> > > are pressed. +	 * The bits 0-2 of the first byte will be
> > > 1s if some buttons are +	 * pressed.
> > > +	 */
> > > +	if (alps_rpt_cmd(psmouse, PSMOUSE_CMD_SETRES,
> > > +			 PSMOUSE_CMD_SETSCALE11, e6))
> > > +		return -EIO;
> > > +
> > > +	if ((e6[0] & 0xf8) != 0 || e6[1] != 0 || (e6[2] != 10 
&&
> > > e6[2] != 100)) +		return -EINVAL;
> > > 
> > >  	if (set_properties) {
> > > 
> > > +		/*
> > > +		 * NOTE: To detect model and trackstick presence we
> 
> need
> 
> > > to do +		 *       full device reset. To speed up
> 
> detection
> 
> > > and prevent +		 *       calling duplicate 
initialization
> > > sequence (both in +		 *       alps_detect() and
> > > alps_init()) we set model/protocol +		 *       version 
and
> > > correct name in alps_init() (which will +		 *       do
> 
> full
> 
> > > device reset). For now set name to DualPoint. +		 */
> > > 
> > >  		psmouse->vendor = "ALPS";
> > > 
> > > -		psmouse->name = dummy.flags & ALPS_DUALPOINT ?
> > > -				"DualPoint TouchPad" : "GlidePoint";
> > > -		psmouse->model = dummy.proto_version << 8;
> > > +		psmouse->name = "DualPoint TouchPad";
> > > 
> > >  	}
> > > 
> > > +
> > > 
> > >  	return 0;
> > 
> > We can't do this; going by e6 only will give us false
> > positives and alps_detect is supposed to be authoritative.
> > 
> > Thanks.
> 
> psmouse-base.c is calling alps_detect() and alps_init()
> consecutively so it does not matter if code is in _detect or
> _init function. Just need to make sure that correct order will
> be used. So this patch could not bring any problems.
> 
> If psmouse-base.c detect device false-positive as ALPS (with
> alps_detect()) then it immediately calls alps_init() which
> fails and psmouse-base.c will try to use another protocol.

Dmitry: PING
Also see my comment for PATCH v3 3/4.

-- 
Pali Rohár
pali.rohar@...il.com

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