linux-kernel - Re: [PATCH 2/4] Input - synaptics: do not release extra buttons once they are pressed

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Date:	Wed, 4 Feb 2015 17:53:56 -0800
From:	Andrew Duggan <aduggan@...aptics.com>
To:	Benjamin Tissoires <benjamin.tissoires@...hat.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:	Hans de Goede <hdegoede@...hat.com>,
	Peter Hutterer <peter.hutterer@...-t.net>,
	linux-input <linux-input@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/4] Input - synaptics: do not release extra buttons once
 they are pressed

On 02/04/2015 01:29 PM, Benjamin Tissoires wrote:
> On Feb 02 2015 or thereabouts, Benjamin Tissoires wrote:
>> On Mon, Feb 2, 2015 at 4:46 PM, Dmitry Torokhov
>> <dmitry.torokhov@...il.com> wrote:
>>> On Wed, Jan 28, 2015 at 03:10:05PM -0500, Benjamin Tissoires wrote:
>>>> The current code releases the extra buttons right after they are pressed.
>>>> As soon as a new serio report comes in, the hw state is reset to 0
>>>> and so the buttons are released.
>>>>
>>>> Check for the report type before acting on the current extra buttons
>>>> state.
>>> No:
>>>
>>> "If Ext is 0 (if bit 1 of bytes 1 and 4 are the same) then there are no
>>> external buttons being pressed (or all external buttons have been
>>> released)." - Synaptics PS/2 TouchPad Interfacing Guide PN:
>>> 511-000275-01 Rev. B
>>>
>> Hmm, indeed, the current code follows the spec. Yeah! a new firmware bug!
>>
>> So when I dumped the ps/2 reports, I clearly saw the release report
>> being sent with the Ext bit to 1, and other reports were in between
>> with no information (because no fingers were on the touchpad).
>>
> OK, so with the hardware, here are the results:
>
> After each incoming event (being a button or touch), when there is no
> more information to send (i.e. touch released or button pressed or
> released), I receive 80 times the following buffer:
> 80 00 00 c0 00 00

Yeah, this is normal. The firmware reports this for 1 second after a 
finger lift. The last paragraph of 3.2 mentions this behavior.

> The number 80 seems quite consistant, though I got once 96.
> Not sure that this repeated buffer might be of interest however.
>
> When a finger is touched on the sensor, I receive the following:
>
> b0 ba 35 c0 8d ed <- first finger down on the sensor
> ....
> b0 ba 3b c0 6f d0
> b0 ba 3b c2 6d d0 <- button 1 pressed
> b0 ba 3b c0 6f d0
> ....
> b0 ba 3b c0 6f d0
> b0 ba 3c c2 6c d0 <- button 1 released
> b0 ba 3c c0 6f d0
> ....
> 90 ba 26 c0 6f d0
> 80 00 00 c0 00 00 <- first finger released from the sensor
> 80 00 00 c0 00 00 <- repeated 80 times
>
> So here, either the spec is wrong, either the Synaptics with FW 8.1 in
> the Lenovos are not following it. But I clearly see that the extended
> buttons are reported only when the Ext bit is 1.

I will have to clarify with those who are more familiar with PS/2. The 
spec might not be up to date since it looks like it was last updated in 
2011.

Andrew

>
> Andrew, could you help us determine which way to go?
> Ideally, could you point out at a firmware version where we could be
> sure that the spec has not been followed so we can add a quirk in the
> driver?
>
> Cheers,
> Benjamin

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