I alternate between two setups on Dell Latitude E6410 laptop: docked and undocked.

The laptop contains this video card:
00:02.0 VGA compatible controller: Intel Corporation Core Processor Integrated Graphics Controller (rev 02) (prog-if 00 [VGA controller])
	Subsystem: Dell Device 040a
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
	Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Interrupt: pin A routed to IRQ 40
	Region 0: Memory at f0000000 (64-bit, non-prefetchable) [size=4M]
	Region 2: Memory at e0000000 (64-bit, prefetchable) [size=256M]
	Region 4: I/O ports at 70b0 [size=8]
	Expansion ROM at <unassigned> [disabled]
	Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit-
		Address: fee0f00c  Data: 4161
	Capabilities: [d0] Power Management version 2
		Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
		Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
	Capabilities: [a4] PCI Advanced Features
		AFCap: TP+ FLR+
		AFCtrl: FLR-
		AFStatus: TP-
	Kernel driver in use: i915
	Kernel modules: i915


Here's the xrandr output for the undocked configuration:
Screen 0: minimum 320 x 200, current 1440 x 900, maximum 8192 x 8192
eDP1 connected 1440x900+0+0 (normal left inverted right x axis y axis) 303mm x 190mm
   1440x900       60.0 +   40.0  
   1024x768       60.0  
   800x600        60.3     56.2  
   640x480        59.9  
VGA1 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)
DP1 disconnected (normal left inverted right x axis y axis)
HDMI2 disconnected (normal left inverted right x axis y axis)
DP2 disconnected (normal left inverted right x axis y axis)
  1440x900 (0xc7)  107.8MHz
        h: width  1440 start 1486 end 1556 total 1928 skew    0 clock   55.9KHz
        v: height  900 start  909 end  918 total  932           clock   60.0Hz


Here's the xrandr output for the docked configuration:
Screen 0: minimum 320 x 200, current 3840 x 1080, maximum 8192 x 8192
eDP1 connected (normal left inverted right x axis y axis)
   1440x900       60.0 +
   1024x768       60.0  
   800x600        60.3     56.2  
   640x480        59.9  
VGA1 disconnected (normal left inverted right x axis y axis)
HDMI1 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 477mm x 268mm
   1920x1080      60.0*+
   1680x1050      60.0  
   1280x1024      75.0     60.0  
   1440x900       59.9  
   1280x960       60.0  
   1280x800       59.8  
   1152x864       75.0  
   1280x720       60.0  
   1024x768       75.1     70.1     60.0  
   832x624        74.6  
   800x600        72.2     75.0     60.3     56.2  
   640x480        72.8     75.0     66.7     60.0  
   720x400        70.1  
DP1 disconnected (normal left inverted right x axis y axis)
HDMI2 connected 1920x1080+1920+0 (normal left inverted right x axis y axis) 477mm x 268mm
   1920x1080      60.0*+
   1680x1050      60.0  
   1280x1024      75.0     60.0  
   1440x900       59.9  
   1280x960       60.0  
   1280x800       59.8  
   1152x864       75.0  
   1280x720       60.0  
   1024x768       75.1     70.1     60.0  
   832x624        74.6  
   800x600        72.2     75.0     60.3     56.2  
   640x480        72.8     75.0     66.7     60.0  
   720x400        70.1  
DP2 disconnected (normal left inverted right x axis y axis)


When switching from the undocked to the docked configuration I try to
use this command:
% xrandr --output VGA1 --off --output DP1 --off --output DP2 --off --output eDP1 --off --output HDMI1 --auto --primary --output HDMI2 --auto --right-of HDMI1

This command always fails with this error:
xrandr: cannot find crtc for output HDMI2

I am able to switch the configuration by running these two commands:
% xrandr --output VGA1 --off --output DP1 --off --output DP2 --off --output eDP1 --off --output HDMI1 --auto --output HDMI2 --off
% xrandr --output VGA1 --off --output DP1 --off --output DP2 --off --output eDP1 --off --output HDMI1 --auto --primary --output HDMI2 --auto --right-of HDMI1


A very similar error occurs when moving back to the undocked
configuration and can be worked around by turning one of the outputs
off and then, in a separate invocation of xrandr, enabling the desired
output.


I understand that the video device only has two CRTCs available, but I
would expect it to work as long as the resulting configuration only
uses two CRTCs.