linux-kernel - Re: [PATCH 1/3] input: alps: Reset mouse before identifying it

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Message-Id: <201410152010.39507@pali>
Date:	Wed, 15 Oct 2014 20:10:39 +0200
From:	Pali Rohár <pali.rohar@...il.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Tommy Will <tommywill2011@...il.com>
Cc:	Hans de Goede <hdegoede@...hat.com>,
	Yunkang Tang <yunkang.tang@...alps.com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] input: alps: Reset mouse before identifying it

On Wednesday 15 October 2014 20:00:11 Dmitry Torokhov wrote:
> On Wed, Oct 15, 2014 at 07:57:37PM +0200, Pali Rohár wrote:
> > On Wednesday 15 October 2014 19:43:15 Dmitry Torokhov wrote:
> > > On Wed, Oct 15, 2014 at 02:53:11PM +0200, Pali Rohár wrote:
> > > > On Tuesday 14 October 2014 08:08:34 Dmitry Torokhov 
wrote:
> > > > > On Fri, Oct 03, 2014 at 11:47:59AM +0200, Hans de
> > > > > Goede
> > 
> > wrote:
> > > > > > Hi,
> > > > > > 
> > > > > > Thanks for working on this!
> > > > > > 
> > > > > > On 10/03/2014 11:43 AM, Pali Rohár wrote:
> > > > > > > On some systems after starting computer function
> > > > > > > alps_identify() does not detect dual ALPS
> > > > > > > touchpad+trackstick device correctly and detect
> > > > > > > only touchpad.
> > > > > > > 
> > > > > > > Resetting ALPS device before identifiying it
> > > > > > > fixing this problem and both parts touchpad and
> > > > > > > trackstick are detected.
> > > > > > > 
> > > > > > > Signed-off-by: Pali Rohár <pali.rohar@...il.com>
> > > > > > > Tested-by: Pali Rohár <pali.rohar@...il.com>
> > > > > > 
> > > > > > Looks good and seems sensible:
> > > > > > 
> > > > > > Acked-by: Hans de Goede <hdegoede@...hat.com>
> > > > > 
> > > > > *sigh* I am not really happy about this, as we making
> > > > > boot longer and longer for people without ALPS
> > > > > touchpads. It would be better if we only reset the
> > > > > mouse when we knew we are dealing with ALPS, and even
> > > > > better if we only reset it when we suspected that we
> > > > > missed trackstick. Any chance of doing this?
> > > > > 
> > > > > Thanks.
> > > > 
> > > > Dmitry, problem is that function check which detecting
> > > > trackstick does not working when I start my laptop from
> > > > power-off state and do not reset PS/2 device. But
> > > > detecting ALPS touchpad looks like working. So if do
> > > > not like this idea, what about doing something like
> > > > this in alps_dectect function?
> > > > 
> > > > int alps_detect(...)
> > > > {
> > > > ...
> > > > /* detect if device is ALPS */
> > > > if (alps_identify(...) < 0)
> > > > return -1;
> > > > /* now we know that device is ALPS */
> > > > if (!(flags & ALPS_DUALPOINT)) {
> > > > /* reset it and identify again, maybe there is
> > > > trackstick */ psmouse_reset(...);
> > > > alps_identify(...);
> > > > }
> > > > ...
> > > > }
> > > > 
> > > > It will does not affect non ALPS devices (because first
> > > > identify call will fail), but will affect ALPS devices
> > > > without trackstick (because identify will be called
> > > > twice and reset too).
> > > 
> > > I think this is a step in right direction. Do you know
> > > what exactly fails in alps_identify() on your box if you
> > > do not call psmouse_reset?
> > > 
> > > Thanks.
> > 
> > Yes, I know. It is failing in alps_probe_trackstick_v3(). It
> > calls alps_command_mode_read_reg(...) and it returns 0 which
> > means trackstick is not there.
> 
> OK, so can we try sticking psmouse_reset() there? This will
> limit the exposure of the new delay.
> 
> Thanks.

Sorry, but I think this is not safe. Function psmouse_reset will 
reset device (set it to relative mode, etc...) and before and 
after alps_probe_trackstick_v3() are called other functions. So 
it could break something else.

Tommy (added To header), what do you think? How could be this 
problem solved? When or where to call psmouse_reset() so that it 
will not affect non ALPS devices and also it call will be safe?

-- 
Pali Rohár
pali.rohar@...il.com

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