This is a bug concerning all linux distributions not only ubuntu. Probably a driver problem. But as asus hasn't released any details on how the chip set works switching its hard to say whats going on.
I can confirm that this bug exists on all version of ubuntu from 12.04 and up (i have tested them all) Setting the different backlight options only controls the light in the keyboard or the internal display but not the external display. Perhaps it is some kind of display switch needed in the lines of optimus. I will investigate this later this week. Please keep this bug open. ** Changed in: linux (Ubuntu) Status: Incomplete => Confirmed -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1205694 Title: 8086:0166 [Taichi 21] external screen is not working properly Status in “linux” package in Ubuntu: Confirmed Bug description: First of all, I'd like to say that both screen are recognized by xrandr: The internal as eDP1 and the external as DP1. The external screen works under some circumstances, but without backlight. If the computer is off, and I turn on with the lid closed, the external screen "works" If the computer is turned on, on linux, and I restart, the external screen keeps "working". If the computer is off and I turn on with the lid opened or the computer is on windows, using the external screen, and I restart to linux, I can't use the external screen: The image keeps "off". Although, the screen is recognized by xrandr, but no setting turns the screen on (not even xrandr --output DP1 --auto) In the situations that the external screen works, the backlight has no effect on it: When I adjust the backlight (either by the hotkeys, or by echo 50 > /sys/class/backlight/acpi_video0/brightness, or echo 3000 > /sys/class/backlight/intel_backlight/brightness), it just adjusts the internal screen When I use the hotkey to turn off the screen, it just turn off the internal screen Also, if I use xrandr to turn off the external screen, or suspend the computer, the external screen is turned off. When I try again to turn on, or resume it doesn't work. I tried to boot with acpi_backlight=vendor, and again just the internal screen worked properly. The hotkey to change the backlight didn't work, but echo 3000 > /sys/class/backlight/intel_backlight/brightness worked I tried to boot with video.use_bios_initial_backlight=0 and the backlight worked just for the internal screen again I tried to boot with acpi_osi="!Windows 2012", the same thing By running dmesg | grep 'ACPI: Video', I get: [ 4.981826] ACPI: Video Device [GFX0] (multi-head: yes rom: no post: no) And lspci | grep VGA shows: 00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics Controller (rev 09) I don't know if I should get 2 results in them, since I have two screens, but in DSDT, I just see one device with methods _DOS, _DOD, so I guess it is right. There is an if in the BCL, checking if it is Windows 8, but I believe acpi_osi="!Windows 2012", should "fix" it if that was the problem I believe that solving the backlight problem when I'm able to turn on the screen might solve the screen not turning on with the lid open. I tried to use the current Mainline kernel (3.11.0-999, or something like that), but after the boot the external screen was off and the internal was on, not showing anything but a black screen. I followed the Kernel/Debugging/Backlight page and I'll submit all the files that it generated. Thank you for your help! ProblemType: Bug DistroRelease: Ubuntu 13.04 Package: linux-image-3.8.0-26-generic 3.8.0-26.38 ProcVersionSignature: Ubuntu 3.8.0-26.38-generic 3.8.13.2 Uname: Linux 3.8.0-26-generic x86_64 ApportVersion: 2.9.2-0ubuntu8.1 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: joao 2437 F.... pulseaudio Date: Sat Jul 27 12:44:02 2013 HibernationDevice: RESUME=UUID=8c6201ab-045c-4bb7-b20d-c4650cca8821 InstallationDate: Installed on 2013-07-23 (4 days ago) InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release amd64 (20130424) MachineType: ASUSTeK COMPUTER INC. TAICHI21 MarkForUpload: True ProcEnviron: TERM=xterm PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=en_US.UTF-8 SHELL=/bin/bash ProcFB: 0 inteldrmfb ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.8.0-26-generic root=UUID=1b4e19b1-47cc-4068-a6d6-b73868b3c9d8 ro quiet splash vt.handoff=7 RelatedPackageVersions: linux-restricted-modules-3.8.0-26-generic N/A linux-backports-modules-3.8.0-26-generic N/A linux-firmware 1.106 SourcePackage: linux UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 01/08/2013 dmi.bios.vendor: American Megatrends Inc. dmi.bios.version: TAICHI21.208 dmi.board.asset.tag: ATN12345678901234567 dmi.board.name: TAICHI21 dmi.board.vendor: ASUSTeK COMPUTER INC. dmi.board.version: 1.0 dmi.chassis.asset.tag: No Asset Tag dmi.chassis.type: 10 dmi.chassis.vendor: ASUSTeK COMPUTER INC. dmi.chassis.version: 1.0 dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrTAICHI21.208:bd01/08/2013:svnASUSTeKCOMPUTERINC.:pnTAICHI21:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnTAICHI21:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0: dmi.product.name: TAICHI21 dmi.product.version: 1.0 dmi.sys.vendor: ASUSTeK COMPUTER INC. --- ApportVersion: 2.12.1-0ubuntu3 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: ubuntu 4118 F.... pulseaudio ubuntu 14584 F.... pulseaudio CasperVersion: 1.336 DistroRelease: Ubuntu 13.10 LiveMediaBuild: Ubuntu 13.10 "Saucy Salamander" - Alpha amd64 (20130904) MachineType: ASUSTeK COMPUTER INC. TAICHI21 MarkForUpload: True Package: linux (not installed) ProcFB: 0 inteldrmfb ProcKernelCmdLine: noprompt cdrom-detect/try-usb=true file=/cdrom/preseed/username.seed boot=casper persistent initrd=/casper/initrd.lz splash -- maybe-ubiquity ProcVersionSignature: Ubuntu 3.11.0-4.9-generic 3.11.0-rc7 RelatedPackageVersions: linux-restricted-modules-3.11.0-4-generic N/A linux-backports-modules-3.11.0-4-generic N/A linux-firmware 1.113 Tags: saucy Uname: Linux 3.11.0-4-generic x86_64 UpgradeStatus: No upgrade log present (probably fresh install) UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo dmi.bios.date: 01/08/2013 dmi.bios.vendor: American Megatrends Inc. dmi.bios.version: TAICHI21.208 dmi.board.asset.tag: ATN12345678901234567 dmi.board.name: TAICHI21 dmi.board.vendor: ASUSTeK COMPUTER INC. dmi.board.version: 1.0 dmi.chassis.asset.tag: No Asset Tag dmi.chassis.type: 10 dmi.chassis.vendor: ASUSTeK COMPUTER INC. dmi.chassis.version: 1.0 dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrTAICHI21.208:bd01/08/2013:svnASUSTeKCOMPUTERINC.:pnTAICHI21:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnTAICHI21:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0: dmi.product.name: TAICHI21 dmi.product.version: 1.0 dmi.sys.vendor: ASUSTeK COMPUTER INC. 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