/usr/lib/unity-settings-daemon/unity-settings-daemon:5:XIQueryDevice:xdevice_get_dimensions:input_info_find_size_match:get_mappable_output_info:do_touchscreen_mapping

The workaround on https://code.launchpad.net/~hui.wang/unity-settings-daemon/unity-settings-daemon-master-touchscreen-fix/+merge/293704 seems to be to workaround the segfault there

in that the description is

"on a Lenovo laptop with the LG LCD panel and the LG touchscreen, when we change the display resolution, the LG touchscreen will be temporarily disconnected from USB host bus for about 0.2 seconds, then will be reconnected to the USB host bus. If we let the system call do_touchscreen_mapping() before the reconnectting, the u-s-d will crash."

so it seems likely that u-s-d gets confused by the screen being removed while configured, maybe some callback not being disconnected when they should...

In the corresponding OEM bug, we have below findings:

"after debug, we found that if we insmod the touchscreen driver after x start, the u-s-d xrandr plugin will not do "do_touchscreen_mapping" function, seems this is a u-s-d xrandr plugin can not support hot plug issue."

"I think an alternative way is fix the u-s-d xrandr plugin can not detect touchscreen hot plug and set variable "priv->main_touchscreen_id" error issue, but as a workaround, we can insmod the touchscreen after X start."

Would be interesting if somebody could try those patches on unity-settings-daemon
https://git.gnome.org/browse/gnome-settings-daemon/commit/?id=311849e
and
https://git.gnome.org/browse/gnome-settings-daemon/commit/?id=ab2b808

those are not going to apply to our codebase though, they are based on the refactoring done in https://git.gnome.org/browse/gnome-settings-daemon/commit/plugins/common/gsd-device-mapper.c?id=bf2f0d5d955f9fe5ca9f880e9f52246016e60e79 which was after we forked and that we didn't rebase on

there are too many different between g-s-d and u-s-d, and also there is not such file named "*device-mapper.c" in u-s-d, so not sure how to try these patch in comment #3.

please refer to http://bazaar.launchpad.net/~jzheng/unity-settings-daemon/unity-settings-daemon-master-touchscreen-fix/revision/4133

tried the patch in comment #3, #4 and #6 on 16.04 and 14.04, got below result:

1, 14.04 (kernel 3.19.0-37, u-s-d: 14.04.20151012, compiz 2014.20150313)
  1.1 without patch
    u-s-d and compiz crashed and system logout after adjust resolution by use display setting at u-c-c (unity-control-center) or use command "xrandr -s 1"
  1.2 with patch
    1.2.1, can not set the resolution by use display setting at u-c-c, the error info please refer to attachment setting-error.jpg
    1.2.2, can change resolution by command "xrandr -s 1" successfully.

2, 16.04 (kernel 4.4.0-21, u-s-d: 16.04.20160209, compiz 16.04.20160415)
  2.1 without patch
    u-s-d crashed once when change resolution by display setting or cmd, but system will not logout, user can continue change resolution without crash.
  2.2 with patch
    same result with without patch.

after patch http://bazaar.launchpad.net/~jzheng/unity-settings-daemon/unity-settings-daemon-master-touchscreen-fix/revision/4133, the dbus interface "org.gnome.SettingsDaemon.XRANDR_2" will lost

could you try how things go with that simple change?

tried https://launchpadlibrarian.net/260326745/usd.patch, got same result with 1.2.1 in comment #7 and same log with #9

@Xinxiu, did you drop your changeset? There is no way that this patch leads to the symbol issue from #9 since it doesn't add that function... also could you get a backtrace with gdb in case it's different?

oops, sorry for comment #13, I started from an error version u-s-d source, this time I patched the simple patch base on unity-settings-daemon-14.04.0+14.04.20151012 which we used in Sutton image and tried again, seems it works fine. the u-s-d works well after change the resolution with patch https://bugs.launchpad.net/ubuntu/+source/unity-settings-daemon/+bug/1503758/+attachment/4666128/+files/usd.patch.

Thanks Xinxiu for testing again, that sounds like good news ;-)

Status changed to 'Confirmed' because the bug affects multiple users.

This bug was fixed in the package unity-settings-daemon - 15.04.1+16.10.20160613-0ubuntu1

---------------
unity-settings-daemon (15.04.1+16.10.20160613-0ubuntu1) yakkety; urgency=medium

  [ Marco Trevisan (Treviño) ]
  * PowerManager: connect to keyboard BrightnessChanged signal to update
    the cached current value properly (LP: #1510344)
  * GsdPowerManager: don't cache kbd backlight current value (LP:
    #1583861)
  * common: backport g-s-d commits for having single shared dbus proxies
  * ScreensaverProxy: redirect supported calls to gnome screensaver APIs
    (LP: #1415265, #1584161)

  [ Robert Ancell ]
  * Correctly check value of XDG_CURRENT_DESKTOP.
  * Remove code for disabling plugin under GNOME Shell - they don't use
    u-s-d.
  * Drop print notifications - not used under Unity.

  [ Sebastien Bacher ]
  * power: '0' keyboard backlight is a valid value (LP: #1510344)
  * Don't hit an xerror when a device is removed while being configured
    (LP: #1503758)
  * wacom: don't segfault when a device is removed while being
    configured. (LP: #1439427)
  * power: fix crasher when the plugin is unloaded (LP: #1567116)
  * power: Add sound notification on power plug/unplug

 -- Marco Trevisan (Treviño) <mail@3v1n0.net> Mon, 13 Jun 2016 11:31:26 +0000

Hello errors.ubuntu.com, or anyone else affected,

Accepted unity-settings-daemon into xenial-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/unity-settings-daemon/15.04.1+16.04.20160701-0ubuntu1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

there are no report from the new version, marking as verified

This bug was fixed in the package unity-settings-daemon - 15.04.1+16.04.20160701-0ubuntu1

---------------
unity-settings-daemon (15.04.1+16.04.20160701-0ubuntu1) xenial; urgency=medium

  [ Robert Ancell ]
  * Correctly check value of XDG_CURRENT_DESKTOP.

  [ Marco Trevisan (Treviño) ]
  * PowerManager: connect to keyboard BrightnessChanged signal to update
    the cached current value properly (LP: #1510344)
  * GsdPowerManager: don't cache kbd backlight current value (LP:
    #1583861)
  * common: backport g-s-d commits for having single shared dbus proxies
  * ScreensaverProxy: redirect supported calls to gnome screensaver APIs
    (LP: #1415265, LP: #1584161)

  [ Sebastien Bacher ]
  * Don't hit an xerror when a device is removed while being configured
    (LP: #1503758)
  * wacom: don't segfault when a device is removed while being
    configured. (LP: #1439427)

  [ Marco Trevisan (Treviño) ]
  * GsdPowerManager: use proper return value for upower_kbd_toggle
    wherever we use it (LP: #1592816)

  [ Kai-Heng Feng ]
  * SettingsManager: Queue up signals before getting D-Bus connection.
    (LP: #1571640)

 -- Marco Trevisan (Treviño) <mail@3v1n0.net> Fri, 01 Jul 2016 13:28:54 +0000

The verification of the Stable Release Update for unity-settings-daemon has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.