[PATCH evdev] Force a button if MT axes are present and it is not a gamepad

[Peter Hutterer]

From: Mauro Carvalho Chehab <mchehab at redhat.com>

We expect at least BTN_TOUCH for anything with MT axes, but devices that
don't have that need a button class regardless. Some gamepads define
MT axes but no buttons, causing a bug in the server when they post a
TouchBegin.

[ 97436.293] (EE) BUG: triggered 'if (!b || !v)'
[ 97436.293] (EE) BUG: exevents.c:929 in UpdateDeviceState()

So, ignore it, if it is a joystick (e. g. if it have BTN_JOYSTICK defined).
Otherwise, fake a button.

This patch basically merges two patches written by Peter Hutterer
<peter.hutterer at who-t.net>.

Signed-off-by: Mauro Carvalho Chehab <mchehab at redhat.com>
Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
 src/evdev.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/evdev.c b/src/evdev.c
index 7b355d7..5667dc1 100644
--- a/src/evdev.c
+++ b/src/evdev.c
@@ -2160,8 +2160,20 @@ EvdevProbe(InputInfoPtr pInfo)
         xf86IDrvMsg(pInfo, X_PROBED, "Found absolute axes\n");
         pEvdev->flags |= EVDEV_ABSOLUTE_EVENTS;
 
-        if (has_mt)
+        if (has_mt) {
             xf86IDrvMsg(pInfo, X_PROBED, "Found absolute multitouch axes\n");
+            if (num_buttons == 0) {
+                if (EvdevBitIsSet(pEvdev->key_bitmask, BTN_JOYSTICK)) {
+                    xf86IDrvMsg(pInfo, X_INFO, "Device is a Joystick with MT without buttons. Ignoring it.\n");
+                    goto out;
+                } else {
+                    xf86IDrvMsg(pInfo, X_INFO, "No buttons found, faking one.\n");
+                    num_buttons = 1;
+                    pEvdev->num_buttons = num_buttons;
+                    pEvdev->flags |= EVDEV_BUTTON_EVENTS;
+                }
+            }
+        }
 
         if ((EvdevBitIsSet(pEvdev->abs_bitmask, ABS_X) &&
              EvdevBitIsSet(pEvdev->abs_bitmask, ABS_Y))) {
@@ -2276,6 +2288,7 @@ EvdevProbe(InputInfoPtr pInfo)
         pEvdev->flags |= EVDEV_RELATIVE_EVENTS;
     }
 
+out:
     if (rc)
         xf86IDrvMsg(pInfo, X_WARNING, "Don't know how to use device\n");
 
-- 
1.8.1