1

Below shows the output from issuing the command xrandr -q:

Screen 0: minimum 8 x 8, current 1600 x 900, maximum 16384 x 16384
DVI-I-0 disconnected (normal left inverted right x axis y axis)
DVI-I-1 disconnected (normal left inverted right x axis y axis)
HDMI-0 disconnected (normal left inverted right x axis y axis)
DP-0 disconnected (normal left inverted right x axis y axis)
DVI-D-0 connected primary 1600x900+0+0 (normal left inverted right x axis y axis) 443mm x 249mm
----- (my comments: info here are removed) -----
DP-1 disconnected (normal left inverted right x axis y axis)

In the start of each line, terms such as DVI-I-0, DVI-I-1, HDMI-0, DP-0, DVI-D-0, DP-1 are used.

Questions:

  1. What does the numbers 0 and 1 mean in these terms? Do they refer to the GPU mentioned by command xrandr --listproviders, i.e. does 0 refer to Provider 0 and 1 refer to Provider1?
  2. What does Screen 0 mean?

Update:
There appears to be no standard or consistent practice on the use of the integer mentioned in question 1. I came to this conclusion after considering 2 configurations on my system, in addition to the answer of @SergiyKolodyazhnny.

Configuration 1: Monitor is connected to DVI socket of Integrated CPU Graphics, UEFI Primary Graphics is set to CPU Graphics and iGPU enabled, and Nouveau driver is used. xrandr and xrandr --listproviders gives:

$ xrandr
Screen 0: minimum 320 x 200, current 1600 x 900, maximum 8192 x 8192
HDMI-2 connected primary 1600x900+0+0 (normal left inverted right x axis y axis) 443mm x 249mm 1600x900      59.98*+
----- (info here are truncated) -----
HDMI-3 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
DVI-I-1-1 disconnected
DVI-D-1-1 disconnected
HDMI-1-1 disconnected
DP-1-1 disconnected

$ xrandr --listproviders
Providers: number : 3
Provider 0: id: 0x6d cap: 0x9, Source Output, Sink Offload crtcs: 3 outputs: 3 associated providers: 2 name:modesetting
Provider 1: id: 0x47 cap: 0x6, Sink Output, Source Offload crtcs: 4 outputs: 4 associated providers: 2 name:nouveau
Provider 2: id: 0x47 cap: 0x6, Sink Output, Source Offload crtcs: 4 outputs: 4 associated providers: 2 name:nouveau

Issues :

  • The integers following the gpu output sockets have added sub-integers and the integers do not appear to related to the integers of the Providers.
  • Monitor is connected to CPU Graphics DVI. However, xrandr reports that monitor is connected to HDMI-2 (which is wrong).
  • xrandr reported 3 Providers but my system only has 2 GPUs installed.

Configuration 2: Monitor is connected to DVI socket of Nvidia Discrete GPU, UEFI Primary Graphics is set to PCIe and iGPU enabled, and Nvidia driver is used. xrandr and xrandr --listproviders gives:

$ xrandr
Screen 0: minimum 8 x 8, current 1600 x 900, maximum 16384 x 16384
DVI-I-0 disconnected (normal left inverted right x axis y axis)
DVI-I-1 connected primary 1600x900+0+0 (normal left inverted right x axis y axis) 443mm x 249mm
   1600x900      59.98*+
----- (info here are truncated) -----
HDMI-0 disconnected (normal left inverted right x axis y axis)
DP-0 disconnected (normal left inverted right x axis y axis)
DVI-D-0 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)

$ xrandr --listproviders
Providers: number : 2
Provider 0: id: 0x29f cap: 0x1, Source Output crtcs: 4 outputs: 6 associated providers: 0 name:NVIDIA-0
Provider 1: id: 0x45 cap: 0x2, Sink Output crtcs: 3 outputs: 3 associated providers: 0 name:modesetting

Issues:

  • DVI-I-1 does not appear related to Provider 1.
  • My Nvidia GPU has 1x DVI-I and 1x DVI-Dsockets. It does not have 2 DVI-I sockets. I was expecting DVI-I-0 to be connected but DVI-I-1 was connected instead. I have also connected the monitor to the Nvidia GPU DVI-D socket; xrandr reports that DVI-D-0 is connected. This result appears intuitively correct but the DVI-I-1 connection seems non-intuitive.

Summary:
There does not appear to be a standard or consistent practice or strategy on the use of the integer to label GPU output sockets by the xrandr command. In the event someone do understand the standard used, or have answers to the issues I have described, please share your answer.

1 Answer 1

0

To answer your second question, screen refers to the X-server you are running at the moment. It is possible to have multiple X-servers running at the same time. So with your typical X server on tty7, and then another instance of X server on tty1, you would have Screen 0 and Screen 1 reported respectively for each tty. This is in fact documented in the manual:

   --screen snum
          This option selects which screen to manipulate. Note this refers to the  X
          screen abstraction, not the monitor (or output).

With the integer numbers, this is not so clear and it is not in the manual. According to Ubuntu Wiki page:

Without parameters, xrandr shows you the names of different outputs available on your system (LVDS, VGA-0, etc.) and resolutions available on each

This doesn't seem to be entirely correct, as the integer values can occasionally change. For instance, in my experience, my VGA port used to be refereed to as VGA-0, but right now it is reported as VGA-1. This post reports same behavior.

According to Appendix A found on this page , the output naming can depend on the graphics card and the driver, and appears to be more related to output port numbers.

1
  • Thanks. :) Noted your explanations on Screen. As for the integer number, there does not appear to be a standard to their use. See also II.2. Outputs naming convention. This is quite unfortunate for me as I was exploring their use to relate to the installed GPUs in a system. I came to the same conclusion too and will add my findings on this matter to my question to highlight this point. Back to the drawing board.
    – Sun Bear
    Apr 18, 2017 at 11:17

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