The RandR 1.2 extension first appeared in Xserver 1.3 (i.e DebianTesting, since 2007-08-21). It provides automatic discovery of modes (resolutions, refresh rates, ...) together with the ability to configure outputs dynamically (resize, rotate, move, ...).
As of today, the following drivers/boards support RandR 1.2:
- the Intel driver on all boards (since 1.9.91),
- the NV driver on G80 and higher boards (since 2.0.95),
- the ATI driver on r200/r300/r400/r500/r600 boards (since 6.7.191) where RandR 1.2 replaces MergedFB,
- the MGA driver on all boards (since 1.9.99)
- the RadeonHD driver on r500/r600 boards (since 1.1)
Other drivers still use the old/hard/non-standard way to configure modes.
I. Cleanup the Xinerama/MergedFB/... config
I.1. Remove options that the driver should query automatically
With the driver detecting modes automatically, several configuration options become useless most of the time in your configuration file (xorg.conf). You might want to remove:
HorizSync from the Monitor section
VertRefresh from the Monitor section
- Modes from Display subsection in Screen section
ModeLine from the Monitor section (but this one is often useful)
I.2. Remove static dual-head configuration
Then, all dual-head related configuration should be removed, it includes:
- dropping dual Device/Screen/Monitor sections, you need keep a single one
dropping MonitorLayout option and Screen lines from the remaining Device section
dropping the ServerLayout section(s)
dropping RightOf/LeftOf indication to the remaining Screen line in ServerLayout section
See http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=420419#27 and below for an example.
Sometimes, thanks to server autoconfiguration, it's also easier to just remove your xorg.conf entirely and see what happens.
II. Use xrandr to enable/disable/move/resize multiple outputs
Once the configuration file (xorg.conf) is updated, starting the server should enable some outputs by default. Their top-left corners will be at the same part of the image, but their modes will probably be different.
All outputs may be configured through xrandr (or the grandr graphic tool). To see the available outputs, just run xrandr:
$ xrandr Screen 0: minimum 320 x 200, current 1400 x 1050, maximum 2048 x 1152 VGA-0 disconnected (normal left inverted right x axis y axis) DVI-0 disconnected (normal left inverted right x axis y axis) LVDS connected 1400x1050+0+0 (normal left inverted right x axis y axis) 0mm x 0mm 1400x1050 60.2*+ 1280x800 60.0 1280x768 60.0 1024x768 60.0 75.0 800x600 60.3 640x480 59.9 S-video disconnected (normal left inverted right x axis y axis)
It shows that this board supports 4 outputs, names VGA-0, DVI-0, LVDS (the internal panel) and S-video (the TV output). Only LVDS is connected and it supports 6 modes at 60 Hz, and one at 75.
The mode marked with a star is the current mode.
The one marked with a plus is the preferred one. Most monitor report a preferred mode to the driver. And the server/driver will generally choose it by default.
II.2. Outputs naming convention
There are no standard naming convention as of today, it just depends on the driver, but it could change in the future.
At least the RadeonHD driver will print out a list of outputs as part of the /var/log/Xorg.0.log file generated by trying to start X. An example of output from the RadeonHD driver is
(II) RADEONHD(0): Output DVI-I_1/digital connected (II) RADEONHD(0): Output DVI-I_1/analog disconnected (II) RADEONHD(0): Output TV_7PIN_DIN disconnected (II) RADEONHD(0): Output DVI-I_2/digital connected (II) RADEONHD(0): Output DVI-I_2/analog disconnected
Where for example "DVI-I_1/digital" is the name of the digital output of the first DVI port.
For the internal laptop panel, external VGA, external DVI and TV, the drivers currently use:
- the Intel driver uses LVDS, VGA, TMDS-1 (TMDS-2, ...), TV
- the ATI driver uses LVDS, VGA-0 (VGA-1, ...), DVI-0 (DVI-1, ...), S-video
- the RadeonHD driver uses PANEL, VGA_1 (VGA_2, ...), DVI-I_1/digital or DVI-I_1/analog (DVI-I_2/digital or DVI-I_1/analog, ...), TV_7PIN_DIN
- the NV driver uses LVDS, VGA0 (VGA1, ...), DVI0 (DVI1, ...), ???
- the MGA driver uses ???, VGA (or VGA1, VGA2, ...), DVI (or DVI1, DVI2, ...), ???
- the Nouveau driver uses LVDS, VGA-1, DVI-I-1, HDMI-1, ???
When manipulating VGA-0 output properties as below, you should use:
$ xrandr --output VGA-0 <options>
II.3. Adding/removing heads dynamically
The old days where you had to restart X when plugging a new monitor are gone. With RandR 1.2, you can plug/unplug monitors whenever you want. Running the following line will query all outputs and enable them with their default mode:
$ xrandr --auto
You may also disable one output using:
$ xrandr --output LVDS --off
This may be useful for some buggy application that don't support multiple outputs well. Also, due to CRTC limitations (see the Caveats section below), it is often required to disable one output before enabling another since most hardware only support 2 at the same time.
II.4. Changing the mode
With the above xrandr output, you may change the LVDS mode to 1024x768 using:
$ xrandr --output LVDS --mode 1024x768
The refresh rate may also be changed, either at the same time or independently:
$ xrandr --output LVDS --mode 1024x768 --rate 75
II.5. Placing outputs in a virtual screen
Randr 1.2 provides the ability to create a large virtual screen and place multiple output in it, either with or without overlapping zones. To reduce memory consumption, drivers will often create a default virtual screen with small dimensions, for instance 1600x1200. Look at the output of xrandr to know your virtual screen dimensions. It would be 2048x1152 if xrandr reports:
$ xrandr Screen 0: minimum 320 x 200, current 1400 x 1050, maximum 2048 x 1152
If you plan to use multiple outputs displaying different zones, you should configure your xorg.conf by adding a Virtual line to subsection Display in the Screen section.
Section "Screen" ... SubSection "Display" Depth 24 Virtual 3000 2000 EndSubSection EndSection
Then you place outputs using xrandr and the --right-of/--left-of/--above/--below options. For instance, to place your VGA output virtually-right of your internal panel, run:
$ xrandr --output VGA --right-of LVDS
Note that hardware and memory limitations may severely restrict the size of your virtual screen, see the Caveats section below.
II.6. Adding new modes
Under some circumstances, some modes might be missing. For instance, if the monitor does not report correct EDID information. Or if the output didn't have a CRTC available at startup because another output was using it and you disabled it in th meantime.
If a mode exist, you may add it to one output with:
$ xrandr --addmode S-video 800x600
If the mode does not exist, you may first create it by passing a modeline:
$ xrandr --newmode <ModeLine>
You may create a modeline using the gtf or cvt utility.
If xrandr says it cannot find S-Video output, you might have to create a little xorg.conf file to help it:
Section "Device" Identifier "radeon" Driver "radeon" Option "ATOMTvOut" "true" EndSection
III. xorg.conf based configuration
Running xrandr is convenient for dynamic configuration, but it may be annoying if you have to run it after every startup of your X server. Section III.6 summarizes all this by showing an example of modern configuration.
III.1. Per Output Config
Before configuring an output, you need to know how to specify it in the config file. To do so, you may add a Monitor-FOO option to the Device section to identify the monitor section for output FOO. For instance:
Section "Device" Identifier "My Graphic Board" ... Option "Monitor-LVDS" "Internal Panel" Option "Monitor-VGA" "External VGA Monitor" EndSection Section "Monitor" Identifier "Internal Panel" ... EndSection Section "Monitor" Identifier "External VGA Monitor" ... EndSection
Then, all output-specific options should go in the corresponding Monitor section.
III.2. Placing outputs
Add the following line to place one monitor on the right of another one as xrandr --output FOO --right-of BAR would do:
Section "Monitor" Identifier "FOO" EndSection Section "Monitor" Identifier "BAR" Option "RightOf" "FOO" EndSection
III.3. Changing DPI and DisplaySize
If your monitor size isn't detected correctly and thus generates a wrong DPI, you need to add a DisplaySize option to the corresponding monitor section. For output FOO, use:
Section "Monitor" Identifier "MyMonitor" DisplaySize 304 228 EndSection Section "Device" ... Option "Monitor-FOO" "MyMonitor" EndSection
III.4. Forcing outputs off or on
If for some reason one output of your graphic board is enabled while it should not, you might want to disable it (for instance because the number of CRTCs available is limited). To do so, add:
Option "Ignore" "true"
If for some reason one output is disabled by the driver (for instance VGA-0 on Radeon Xpress 200 because load detection is not reliable in the driver yet), you might want to enable it by force. To do so, add:
Option "Enable" "true"
Then, you might need to add modes since such an output may not query modes correctly. See "Forcing a preferred mode" to do so.
III.5. Forcing a preferred mode
This is one of rare cases where the ModeLine open is still useful these days. If the preferred mode reported by your monitor isn't the one you want by default, or if there is no preferred mode and the driver does not choose the right one, you might want to force another mode on an output.
Assuming you want to force 1280x1024 at 75Hz at startup, add something like the following to the Monitor section:
Modeline "1280x1024_75.00" 138.54 1280 1368 1504 1728 1024 1025 1028 1069 -HSync +Vsync Option "PreferredMode" "1280x1024_75.00"
The ModeLine line may be obtained by looking at your current Xorg.0.log if the mode is already detected (when it appears in the output of xrandr). Or you may generate a new one using:
$ gtf 1280 1024 75 Modeline "1280x1024_75.00" 138.54 1280 1368 1504 1728 1024 1025 1028 1069 -HSync +Vsync
III.6. Example of modern configuration
Here's an example of xorg.conf for a ATI board with DVI-0 (with DisplaySize and preferred mode forced), LVDS (placed on the right of DVI-0) and VGA-0 (disabled) outputs.
Section "InputDevice" Identifier "Generic Keyboard" Driver "keyboard" Option "CoreKeyboard" Option "XkbRules" "xorg" Option "XkbModel" "pc101" Option "XkbLayout" "us" EndSection Section "InputDevice" Identifier "Configured Mouse" Driver "mouse" Option "CorePointer" Option "Device" "/dev/input/mice" Option "Protocol" "ImPS/2" Option "Emulate3Buttons" "true" Option "ZAxisMapping" "4 5" EndSection # external DVI with DisplaySize and preferred mode overriden Section "Monitor" Identifier "External DVI" DisplaySize 304 228 Modeline "1280x1024_60.00" 108.88 1280 1360 1496 1712 1024 1025 1028 1060 -HSync +Vsync Option "PreferredMode" "1280x1024_60.00" EndSection # internal laptop panel to place on the right of DVI-0 Section "Monitor" Identifier "Integrated LCD" Option "RightOf" "External DVI" EndSection # disable VGA by default Section "Monitor" Identifier "VGA-0" Option "Ignore" "true" EndSection Section "Device" Identifier "ATI Technologies, Inc. M22 [Radeon Mobility M300]" Driver "ati" BusID "PCI:1:0:0" Option "AccelMethod" "EXA" Option "Monitor-DVI-0" "External DVI" Option "Monitor-LVDS" "Integrated LCD" # no need to specific Monitor-VGA-0, it uses the "VGA-0" identifier automatically EndSection Section "Screen" Identifier "Default Screen" Device "ATI Technologies, Inc. M22 [Radeon Mobility M300]" DefaultDepth 24 SubSection "Display" Depth 24 # big virtual screen to place Virtual 3072 1200 EndSubSection EndSection Section "ServerLayout" Identifier "Default Layout" Screen "Default Screen" InputDevice "Generic Keyboard" InputDevice "Configured Mouse" EndSection
IV. Debugging problems
IV.1. Monitor quirks
Some hardware do not report correct information, especially lots of monitors report wrong EDID. In this case, the server/driver might detect some incorrect modes or miss some of them. In some cases, you will not be able to get your desired large resolution. In some other cases, you could get a black screen.
The best solution might be to add a quirk in the X server to work around hardware problems. If this happens to you, you might want to report a bug at http://bugzilla.freedesktop.org and provide detailled information including a precise identifier for your monitor. See https://bugs.freedesktop.org/show_bug.cgi?id=11603 for an example.
IV.2. Remote RandR configuration
If for some reason your X server just gives a blank screen at startup, especially because of incorrect modes, it might look hard for you to fix it since you can't use a terminal within the broken X to fix X. Fortunately, xrandr supports configuration of distant servers, using either the DISPLAY environment variable or the -display option:
xrandr -display :0.0 ...
This way, if you have access to a VT console (with Ctrl-Alt-F1) or (better) if you can log in remotely through ssh, you might manage to select a correct mode.
V. Output specific properties
Each output may have several specific properties. For instance, the TV output has a tv_standard property to choose between PAL and NTSC. To see the values of properties, you should run:
$ xrandr --verbose tv_standard: ntsc
To change the TV standard, use something like:
$ xrandr --output S-video --set tv_standard pal
Additionally, some drivers such as ATI as of 6.7.195 disabling load detection on the TV output since it leads to TV wrongly being detected as connected, and thus a CRTC being wasted.
$ xrandr --verbose load_detection: 0 (0x00000000) range: (0,1)
To reenable load-detection, just run
$ xrandr --output S-video --set load_detection 1
Some modes might need to be added then, see section Adding new modes above.
There is currently no way to specify output properties from xorg.conf.
VI.1. Virtual screen size
The dimensions of the virtual screen (Virtual line in subsection Display) may be severely constrained by memory consumption.
Also, the hardware does not support unlimited coordinates. For instance, Intel boards up to i945 only support 2048 pixels in each direction. If you enable a larger virtual screen, DRI will be disabled and some problems may appear.
Most hardware only have 2 CRTCs, which means they only have 2 rendering pipeline and thus may only display on 2 outputs at the same time. This is why you may have to disable one output before being able to enable another one.
See http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=439322#52 for an example.
2 outputs may only use the same CRTC in clone mode, i.e. if they use the exact same mode.
Some outputs may also be restricted to some CRTC. xrandr --verbose gives information on which CRTC are available/used for each output. For instance, below, LVDS uses CRTC #0 and may not use any other one. VGA-0 uses none currently and may use #0 or #1.
VGA-0 disconnected (normal left inverted right x axis y axis) CRTCs: 0 1 LVDS connected 1400x1050+0+0 (0x50) normal (normal left inverted right x axis y axis) 0mm x 0mm CRTC: 0 CRTCs: 0
In case of problems, xrandr --crtc may be used to force another CRTC for some output.
VI.3. XV Overlay on only one display
(This is not really new to RandR 1.2 but more people are experiencing this issue nowadays)
The hardware may only display the X-Video overlay (basically the image generated by video players) on one output at the same time. So, if a video window appears on two outputs at the same time, the X-Video content with only appear on one of them, the other monitor will keep a black image. To move the X-Video overlay to the second CRTC, use:
xvattr -a XV_CRTC -v 1
(to move to the first CRTC, use -v 0).
The other way to solve this issue is to not have the same part of the screen on both outputs. The driver will automatically place the X-Video overlay on the CRTC where most of the X-Video window is.
VI.4. Old dual-head configs broken
RandR 1.2 aware drivers do not support old dual-head configs anymore. It will even crash the X server at startup.
VI.5. Multi-board support broken
RandR 1.2 does not support multiple boards yet (it's planned for RandR 1.3). It means that any RandR 1.2 aware driver will crash the server if you have 2 boards. Even one board with a RandR 1.2 driver and another board with a classic driver does not work. It just crashes the X server.
VI.6. No more multiple independent desktop
RandR 1.2 provides a big virtual screen where all outputs are placed. It is great if you like moving windows between monitors. But lots of people were used to have a single board with multiple independent monitors with one window manager on each of them. It's for instance nice if you want to switch between virtual desktops on one monitor without moving on the other one.
It is not possible anymore with RandR 1.2 unless the window manager implements it, which is pretty rare as of today (only Enlightenment 17, XMonad and awesome do it). As a small workaround, most window manager have the ability to pin a window on all virtual desktop, which implements N desktop on one head x 1 single desktop on the other head.
In case of multiple boards, it is not clear what will happen since RandR 1.2 does not support it yet (see the above section). Having a shared virtual screen between multiple boards might be hard.