screen calibrate does not recognize screen taps

[Chris Gregan]

Summary:
Calibrate applet no longer registers screen touch. Cannot calibrate screen on Q1

Steps to Reproduce:
1) Launch calibrate app on Q1
2) Tap screen where flashing target appears

Expected result:
Target accepts tap and moves to lower left corner

Actual result:
Tap is not acknowledged, screen cannot be calibrated

[cathyli (cathy-li)]

Todd, I found the issue in moblin-applets 0.59-0ubuntu1, pls. have a look at.

[cathyli (cathy-li)]

I met the same issue in Ubuntu beta4 image, the issue happened on menlow platform with LCD kit.

[Chris Gregan (cgregan)]

Confirmed on Jax10 with Acton build 20080502

[Chris Gregan (cgregan)]

Correction. I just tried holding the stylus on the blinking target for a few seconds and the calibration does continue. Looks like Acton 20080502 is not affected.

That being said, UME Beta 4 is not so lucky. Defect is active for UME.

[Tony Espy (awe)]

Marking invalid as per Chris' last comment.

[ToddBrandt (todd-e-brandt)]

The problem is with the kernel. The evtouch module is supposed to emit binary coordinate data through /dev/input/touchscreen. It did so properly in the 2.22 kernel we used in GASTON, but in hardy the kernel is new and somehow has that feature turned off.

[Loïc Minier (lool)]

@Todd: which option is missing?

@Amit: could you make sure we get this support in our kernel?

[ToddBrandt (todd-e-brandt)]

Ok, I found the problem and have a fix. This actually is a security bug in the kernel and a misuse of the kernel's evdev module in the new version of the xorg evtouch driver. The new evtouch driver that's being installed with hardy is calling an evdev ioctl that allows it to assume exclusive control over the data coming from the touchscreen (ioctl(local->fd, EVIOCGRAB, (void *)1)). The problem is that if xorg cuts off access to everyone else but the xserver, external calibrators won't work or any other piece of code that wants to harmlessly access the data coming from /dev/input/touchscreen. I see this as a security issue as well because what if someone writes a little init.d trojan that calls EVIOCGRAB before xserver has started? The xserver would probably crash.

The buggy package is xserver-xorg-input-evtouch_0.8.7-3ubuntu1_lpia.deb, and I've created a new version with a patch that removes this exclusive control call. I'll be uploading it to the PPA shortly. Here's the patch:

--- xf86-input-evtouch-0.8.7/evtouch.c 2008-05-14 20:17:39.000000000 +0000
+++ xf86-input-evtouch-0.8.7-good/evtouch.c 2008-05-14 20:12:22.000000000 +0000
@@ -499,9 +499,10 @@

         xf86FlushInput(local->fd);

+#if 0
         if (ioctl(local->fd, EVIOCGRAB, (void *)1))
                 xf86Msg(X_ERROR, "%s: Unable to grab device (%s).\n", local->name, strerror(errno));
-
+#endif

 #ifndef XFREE86_V4
         xf86AddEnabledDevice(local);

[ToddBrandt (todd-e-brandt)]

ok, I just uploaded xf86-input-evtouch_0.8.7-3ubuntu2_source.changes to the ubuntu-mobile ppa with the fixed version of this evtouch driver package. It should be online in an hour or so.

[cathyli (cathy-li)]

Verified in xserver-xorg-input-evtouch: 0.8.7-3ubuntu2, screen calibrate can recognize screen taps now, close the issue.

[Steve Kowalik (stevenk)]

I have verified that this is fixed in the 20080519.1 daily build.

[Chris Gregan (cgregan)]

Fix confirmed on Q1U with UME Daily 20080527