[PATCH 4.0 REGRESSION FIX 0/1] alps: Fix left touchpad button getting stuck

[PATCH 4.0 REGRESSION FIX 0/1] alps: Fix left touchpad button getting stuck

[Hans de Goede]

Hi Linus, Dmitry,

Sorry for the last minute regression fix, but the existence of this regression
was not entirely clear until Hans de Bruin send a very clear reproducer this
morning.

I'm not sure if this is 4.0 material, it does fix a real regression, the fix
is pretty simple and safe (*), and when triggered the behavior (stuck mouse
button) is nasty, which all counts in favor of fixing this. OTOH this only
affects somewhat older hardware and only a certain usage pattern (using the
trackpoint with the touchpad buttons). Anyways the call if this is 4.0 material
is up to you (Linus and Dmitry), I'm just trying to make sure you're aware of
this issue and the patch.

The details of the actual bug + fix can be found in the commit msg of the
patch.

Regards,

Hans

*) The fix restores 3.19 behavior for alps v2 dualpoint touchpad/stick combos

[PATCH 4.0 REGRESSION FIX] alps: Fix left touchpad button getting stuck when using it with trackpoint

[Hans de Goede]

When the left touchpad button gets pressed, and then the trackpoint is moved,
and then the button is released, the following happens:

1) touchpad packet is received, touchpad evdev node reports BTN_LEFT 1
2) pointingstick packet is received, the hw will report a BTN_LEFT 1 in this
   packet because when the trackstick is active it communicates the combined
   touchpad + pointingstick buttons in the trackstick packet, since
   alps_report_bare_ps2_packet passes NULL (*) for the dev2 parameter to
   alps_report_buttons the combining is not detected and the pointingstick
   evdev node will also report BTN_LEFT 1
3) on release of the button a pointingstick packet with BTN_LEFT 0 is received,
   and the pointingstick evdev node will report BTN_LEFT 0

Note how because of the passing as NULL for dev2 the touchpad evdev node
will never send BTN_LEFT 0 in this scenario leading to a stuck mouse button.

This is a regression in 4.0 introduced by commit 04aae283ba6a8
("Input: ALPS - do not mix trackstick and external PS/2 mouse data")

This commit fixes this by passing in the touchpad evdev as dev2 parameter
when calling alps_report_buttons for the pointingstick on alps v2 devices,
so that alps_report_buttons correctly detect that we're already reporting the
button as pressed via the touchpad evdev node, and will also send the release
event there.

Reported-by: Hans de Bruin <jmdebruin@xmsnet.nl>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/input/mouse/alps.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/input/mouse/alps.c b/drivers/input/mouse/alps.c
index 80b6eca..6962c26 100644
--- a/drivers/input/mouse/alps.c
+++ b/drivers/input/mouse/alps.c
@@ -1159,13 +1159,14 @@ static void alps_report_bare_ps2_packet(struct psmouse *psmouse,
 					bool report_buttons)
 {
 	struct alps_data *priv = psmouse->private;
-	struct input_dev *dev;
+	struct input_dev *dev, *dev2 = NULL;
 
 	/* Figure out which device to use to report the bare packet */
 	if (priv->proto_version == ALPS_PROTO_V2 &&
 	    (priv->flags & ALPS_DUALPOINT)) {
 		/* On V2 devices the DualPoint Stick reports bare packets */
 		dev = priv->dev2;
+		dev2 = psmouse->dev;
 	} else if (unlikely(IS_ERR_OR_NULL(priv->dev3))) {
 		/* Register dev3 mouse if we received PS/2 packet first time */
 		if (!IS_ERR(priv->dev3))
@@ -1177,7 +1178,7 @@ static void alps_report_bare_ps2_packet(struct psmouse *psmouse,
 	}
 
 	if (report_buttons)
-		alps_report_buttons(dev, NULL,
+		alps_report_buttons(dev, dev2,
 				packet[0] & 1, packet[0] & 2, packet[0] & 4);
 
 	input_report_rel(dev, REL_X,
-- 
2.3.4

Re: [PATCH 4.0 REGRESSION FIX] alps: Fix left touchpad button getting stuck when using it with trackpoint

[Pali Rohár]

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On Wednesday 08 April 2015 17:38:52 Hans de Goede wrote:
> When the left touchpad button gets pressed, and then the
> trackpoint is moved, and then the button is released, the
> following happens:
> 
> 1) touchpad packet is received, touchpad evdev node reports
> BTN_LEFT 1 2) pointingstick packet is received, the hw will
> report a BTN_LEFT 1 in this packet because when the
> trackstick is active it communicates the combined touchpad +
> pointingstick buttons in the trackstick packet, since
> alps_report_bare_ps2_packet passes NULL (*) for the dev2
> parameter to alps_report_buttons the combining is not
> detected and the pointingstick evdev node will also report
> BTN_LEFT 1
> 3) on release of the button a pointingstick packet with
> BTN_LEFT 0 is received, and the pointingstick evdev node will
> report BTN_LEFT 0
> 
> Note how because of the passing as NULL for dev2 the touchpad
> evdev node will never send BTN_LEFT 0 in this scenario
> leading to a stuck mouse button.
> 
> This is a regression in 4.0 introduced by commit 04aae283ba6a8
> ("Input: ALPS - do not mix trackstick and external PS/2 mouse
> data")
> 
> This commit fixes this by passing in the touchpad evdev as
> dev2 parameter when calling alps_report_buttons for the
> pointingstick on alps v2 devices, so that alps_report_buttons
> correctly detect that we're already reporting the button as
> pressed via the touchpad evdev node, and will also send the
> release event there.
> 
> Reported-by: Hans de Bruin <jmdebruin@xmsnet.nl>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Patch looks good to me, so

Acked-by: Pali Rohár <pali.rohar@gmail.com>

As this is regression in 4.0 (which was not in 3.19), I'm also 
for fixing it. But decision is of course on maintainers...

I think this is nice example how touchpad+trackstick protocol at 
HW level should not looks like. It is complete mess what HW 
engineers invented and how their devices pass input data to 
operating system.

> ---
>  drivers/input/mouse/alps.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/input/mouse/alps.c
> b/drivers/input/mouse/alps.c index 80b6eca..6962c26 100644
> --- a/drivers/input/mouse/alps.c
> +++ b/drivers/input/mouse/alps.c
> @@ -1159,13 +1159,14 @@ static void
> alps_report_bare_ps2_packet(struct psmouse *psmouse, bool
> report_buttons)
>  {
>  	struct alps_data *priv = psmouse->private;
> -	struct input_dev *dev;
> +	struct input_dev *dev, *dev2 = NULL;
> 
>  	/* Figure out which device to use to report the bare packet
> */ if (priv->proto_version == ALPS_PROTO_V2 &&
>  	    (priv->flags & ALPS_DUALPOINT)) {
>  		/* On V2 devices the DualPoint Stick reports bare packets
> */ dev = priv->dev2;
> +		dev2 = psmouse->dev;
>  	} else if (unlikely(IS_ERR_OR_NULL(priv->dev3))) {
>  		/* Register dev3 mouse if we received PS/2 packet first
> time */ if (!IS_ERR(priv->dev3))
> @@ -1177,7 +1178,7 @@ static void
> alps_report_bare_ps2_packet(struct psmouse *psmouse, }
> 
>  	if (report_buttons)
> -		alps_report_buttons(dev, NULL,
> +		alps_report_buttons(dev, dev2,
>  				packet[0] & 1, packet[0] & 2, packet[0] & 4);
> 
>  	input_report_rel(dev, REL_X,

-- 
Pali Rohár
pali.rohar@gmail.com

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Re: [PATCH 4.0 REGRESSION FIX] alps: Fix left touchpad button getting stuck when using it with trackpoint

[Dmitry Torokhov]

On Wed, Apr 08, 2015 at 10:26:36PM +0200, Pali Rohár wrote:
> On Wednesday 08 April 2015 17:38:52 Hans de Goede wrote:
> > When the left touchpad button gets pressed, and then the
> > trackpoint is moved, and then the button is released, the
> > following happens:
> > 
> > 1) touchpad packet is received, touchpad evdev node reports
> > BTN_LEFT 1 2) pointingstick packet is received, the hw will
> > report a BTN_LEFT 1 in this packet because when the
> > trackstick is active it communicates the combined touchpad +
> > pointingstick buttons in the trackstick packet, since
> > alps_report_bare_ps2_packet passes NULL (*) for the dev2
> > parameter to alps_report_buttons the combining is not
> > detected and the pointingstick evdev node will also report
> > BTN_LEFT 1
> > 3) on release of the button a pointingstick packet with
> > BTN_LEFT 0 is received, and the pointingstick evdev node will
> > report BTN_LEFT 0
> > 
> > Note how because of the passing as NULL for dev2 the touchpad
> > evdev node will never send BTN_LEFT 0 in this scenario
> > leading to a stuck mouse button.
> > 
> > This is a regression in 4.0 introduced by commit 04aae283ba6a8
> > ("Input: ALPS - do not mix trackstick and external PS/2 mouse
> > data")
> > 
> > This commit fixes this by passing in the touchpad evdev as
> > dev2 parameter when calling alps_report_buttons for the
> > pointingstick on alps v2 devices, so that alps_report_buttons
> > correctly detect that we're already reporting the button as
> > pressed via the touchpad evdev node, and will also send the
> > release event there.
> > 
> > Reported-by: Hans de Bruin <jmdebruin@xmsnet.nl>
> > Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> 
> Patch looks good to me, so
> 
> Acked-by: Pali Rohár <pali.rohar@gmail.com>
> 
> As this is regression in 4.0 (which was not in 3.19), I'm also 
> for fixing it. But decision is of course on maintainers...

Doh! Missed the 4.0 so had to tag it for stable.

-- 
Dmitry
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