[PATCH] Input: synaptics - checking Extbit when passing ext_buttons to pt_port

We found a problem on couples of Lenovo laptop models, when we press
down the extend button of trackstick (IBM trackpoint), the driver will
report both key_down and key_up events to the userspace, while we
release that button, the driver won't report any events to the
userspace.

Through debugging, we found when we press down or release the extend
button, the hardware will report more than one packets to the driver,
only one packet is valid (Extbit is set to 1), the rest of the
packets only contain zero. The current driver won't drop those
invalid packets but regard them as ext_button packets and pass them
to the pt_port, unfortunately the zero means key release, as a
result the userspace get the key_up event immediately following the
key_down event.

Adding an Extbit check before passing ext_buttons to pt_port can
drop all invalid packets and fix this problem.

Signed-off-by: Hui Wang <redacted>
---
 drivers/input/mouse/synaptics.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c
index 6025eb4..ad81140 100644
--- a/drivers/input/mouse/synaptics.c
+++ b/drivers/input/mouse/synaptics.c

@@ -880,9 +880,11 @@ static void synaptics_report_ext_buttons(struct psmouse *psmouse,
 	/*
 	 * This generation of touchpads has the trackstick buttons
 	 * physically wired to the touchpad. Re-route them through
-	 * the pass-through interface.
+	 * the pass-through interface. And only pass extend button
+	 * events to pt_port when ExtBit is 1.
 	 */
-	if (!priv->pt_port)
+	if (!priv->pt_port ||
+	    !((psmouse->packet[0] ^ psmouse->packet[3]) & 0x02))
 		return;
 
 	/* The trackstick expects at most 3 buttons */

-- 
1.9.1

Hi Hui,

On Tue, Mar 15, 2016 at 4:45 AM, Hui Wang [off-list ref] wrote:

We found a problem on couples of Lenovo laptop models, when we press
down the extend button of trackstick (IBM trackpoint), the driver will
report both key_down and key_up events to the userspace, while we
release that button, the driver won't report any events to the
userspace.

Through debugging, we found when we press down or release the extend
button, the hardware will report more than one packets to the driver,
only one packet is valid (Extbit is set to 1), the rest of the
packets only contain zero. The current driver won't drop those
invalid packets but regard them as ext_button packets and pass them
to the pt_port, unfortunately the zero means key release, as a
result the userspace get the key_up event immediately following the
key_down event.

Adding an Extbit check before passing ext_buttons to pt_port can
drop all invalid packets and fix this problem.

Signed-off-by: Hui Wang <redacted>

Could you check if the patch I posted this morning fixes your problem?:
https://patchwork.kernel.org/patch/8587101/

The issue with yours is that it will change the behavior for all
generation of synaptics devices and might introduce regressions.

Cheers,
Benjamin

On 03/15/2016 10:21 PM, Benjamin Tissoires wrote:

Hi Hui,

On Tue, Mar 15, 2016 at 4:45 AM, Hui Wang [off-list ref] wrote:

quoted

We found a problem on couples of Lenovo laptop models, when we press
down the extend button of trackstick (IBM trackpoint), the driver will
report both key_down and key_up events to the userspace, while we
release that button, the driver won't report any events to the
userspace.

Through debugging, we found when we press down or release the extend
button, the hardware will report more than one packets to the driver,
only one packet is valid (Extbit is set to 1), the rest of the
packets only contain zero. The current driver won't drop those
invalid packets but regard them as ext_button packets and pass them
to the pt_port, unfortunately the zero means key release, as a
result the userspace get the key_up event immediately following the
key_down event.

Adding an Extbit check before passing ext_buttons to pt_port can
drop all invalid packets and fix this problem.

Signed-off-by: Hui Wang <redacted>

Could you check if the patch I posted this morning fixes your problem?:
https://patchwork.kernel.org/patch/8587101/

The issue with yours is that it will change the behavior for all
generation of synaptics devices and might introduce regressions.

Cheers,
Benjamin

Yes, it can fix the problem on the machines I tested.

By the way, according to the page 29 of Synaptics PS/2 TouchPad Interfacing Guide Rev. B, the extended button event is only reported when Extbit is set to 1, I think all generation firmware should follow this guide, why do we need to check the firmware version here?


Thanks,
Hui.

quoted

---
  drivers/input/mouse/synaptics.c | 6 ++++--
  1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c
index 6025eb4..ad81140 100644
--- a/drivers/input/mouse/synaptics.c
+++ b/drivers/input/mouse/synaptics.c

@@ -880,9 +880,11 @@ static void synaptics_report_ext_buttons(struct psmouse *psmouse,
         /*
          * This generation of touchpads has the trackstick buttons
          * physically wired to the touchpad. Re-route them through
-        * the pass-through interface.
+        * the pass-through interface. And only pass extend button
+        * events to pt_port when ExtBit is 1.
          */
-       if (!priv->pt_port)
+       if (!priv->pt_port ||
+           !((psmouse->packet[0] ^ psmouse->packet[3]) & 0x02))
                 return;

         /* The trackstick expects at most 3 buttons */
--

1.9.1

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On Wed, Mar 16, 2016 at 2:33 AM, Hui Wang [off-list ref] wrote:

On 03/15/2016 10:21 PM, Benjamin Tissoires wrote:

quoted

Hi Hui,

On Tue, Mar 15, 2016 at 4:45 AM, Hui Wang [off-list ref] wrote:

quoted

We found a problem on couples of Lenovo laptop models, when we press
down the extend button of trackstick (IBM trackpoint), the driver will
report both key_down and key_up events to the userspace, while we
release that button, the driver won't report any events to the
userspace.

Through debugging, we found when we press down or release the extend
button, the hardware will report more than one packets to the driver,
only one packet is valid (Extbit is set to 1), the rest of the
packets only contain zero. The current driver won't drop those
invalid packets but regard them as ext_button packets and pass them
to the pt_port, unfortunately the zero means key release, as a
result the userspace get the key_up event immediately following the
key_down event.

Adding an Extbit check before passing ext_buttons to pt_port can
drop all invalid packets and fix this problem.

Signed-off-by: Hui Wang <redacted>

Could you check if the patch I posted this morning fixes your problem?:
https://patchwork.kernel.org/patch/8587101/

The issue with yours is that it will change the behavior for all
generation of synaptics devices and might introduce regressions.

Cheers,
Benjamin

Yes, it can fix the problem on the machines I tested.

By the way, according to the page 29 of Synaptics PS/2 TouchPad Interfacing
Guide Rev. B, the extended button event is only reported when Extbit is set
to 1, I think all generation firmware should follow this guide, why do we
need to check the firmware version here?

That's what I first thought, but Dmitry showed me I was wrong. See
http://www.spinics.net/lists/linux-input/msg36349.html
If the bit is not set, there is no button pressed, so we should release them.

Synaptics was aware of the problem, promised to fix it but it looks
like it fells through the cracks.

Cheers,
Benjamin

Thanks,
Hui.

quoted

quoted

---
  drivers/input/mouse/synaptics.c | 6 ++++--
  1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/input/mouse/synaptics.c

b/drivers/input/mouse/synaptics.c
index 6025eb4..ad81140 100644

--- a/drivers/input/mouse/synaptics.c
+++ b/drivers/input/mouse/synaptics.c

@@ -880,9 +880,11 @@ static void synaptics_report_ext_buttons(struct

psmouse *psmouse,
         /*
          * This generation of touchpads has the trackstick buttons
          * physically wired to the touchpad. Re-route them through
-        * the pass-through interface.
+        * the pass-through interface. And only pass extend button
+        * events to pt_port when ExtBit is 1.
          */
-       if (!priv->pt_port)
+       if (!priv->pt_port ||
+           !((psmouse->packet[0] ^ psmouse->packet[3]) & 0x02))
                 return;

         /* The trackstick expects at most 3 buttons */
--
1.9.1

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