Appendix C. Display Device Names

A "display device" refers to a hardware device capable of displaying an image. Most NVIDIA GPUs can drive multiple display devices simultaneously.

Many X configuration options can be used to separately configure each display device in use by the X screen. To address an individual display device, you can use one of several names that are assigned to it.

For example, the "ModeValidation" X configuration option by default applies to all display devices on the X screen. E.g.,

    Option "ModeValidation" "NoMaxPClkCheck"

You can use a display device name qualifier to configure each display device's ModeValidation separately. E.g.,

    Option "ModeValidation" "DFP-0: NoMaxPClkCheck; CRT-1: NoVesaModes"

The description of each X configuration option in Appendix B, X Config Options provides more detail on the available syntax for each option.

The available display device names vary by GPU. To find all available names for your configuration, start the X server with verbose logging enabled (e.g., startx -- -logverbose 5, or enable the "ModeDebug" X configuration option with nvidia-xconfig --mode-debug and restart the X server).

The X log (normally /var/log/Xorg.0.log) will contain a list of what display devices are valid for the GPU. E.g.,

(--) NVIDIA(0): Valid display device(s) on Quadro 6000 at PCI:10:0:0
(--) NVIDIA(0):     CRT-0
(--) NVIDIA(0):     CRT-1
(--) NVIDIA(0):     DELL U2410 (DFP-0) (connected)
(--) NVIDIA(0):     NEC LCD1980SXi (DFP-1) (connected)

The X log will also contain a list of which display devices are assigned to the X screen. E.g.,

(II) NVIDIA(0): Display device(s) assigned to X screen 0:
(II) NVIDIA(0):   CRT-0
(II) NVIDIA(0):   CRT-1
(II) NVIDIA(0):   DELL U2410 (DFP-0)
(II) NVIDIA(0):   NEC LCD1980SXi (DFP-1)

Note that when multiple X screens are configured on the same GPU, the NVIDIA X driver assigns different display devices to each X screen. On X servers that support RandR 1.2 or later, the NVIDIA X driver will create an RandR output for each display device assigned to an X screen.

The X log will also report a list of "Name Aliases" for each display device. E.g.,

(--) NVIDIA(0): Name Aliases for NEC LCD1980SXi (DFP-1):
(--) NVIDIA(0):   DFP
(--) NVIDIA(0):   DFP-1
(--) NVIDIA(0):   DPY-3
(--) NVIDIA(0):   DVI-I-3
(--) NVIDIA(0):   DPY-EDID-373091cb-5c07-6430-54d2-1112efd64b44

These aliases can be used interchangeably to refer to the same display device in any X configuration option, as an nvidia-settings target specification, or in NV-CONTROL protocol that uses similar strings, such as NV_CTRL_STRING_CURRENT_METAMODE_VERSION_2 (available through the nvidia-settings command line as nvidia-settings --query CurrentMetaMode).

Each alias has different properties that may affect which alias is appropriate to use. The possible alias names are:

When DisplayPort 1.2 branch devices are present, display devices will be created with type- and connector-based names that are based on how they are connected to the branch device tree. For example, if a connector named DP-2 has a branch device attached and a DisplayPort device is connected to the branch device's first downstream port, a display device named DP-2.1 might be created. If another branch device is connected between the first branch device and the display device, the name might be DP-2.1.1.

To avoid cluttering the output list, DisplayPort 1.2 devices can be deleted when they are no longer connected and are not named in any MetaModes. This behavior can be enabled with the DeleteUnusedDP12Displays option.

Any display device name can have an optional GPU qualifier prefix. E.g., "GPU-0.DVI-I-3". This is useful in Mosaic configurations: type- and connector-based display device names are only unique within a GPU, so the GPU qualifier is used to distinguish between identically named display devices on different GPUs. For example:

    Option "MetaModes"   "GPU-0.CRT-0: 1600x1200, GPU-1.CRT-0: 1024x768"

If no GPU is specified for a particular display device name, the setting will apply to any devices with that name across all GPUs. Note that the GPU UUID can also be used as the qualifier. E.g., "GPU-758a4cf7-0761-62c7-9bf7-c7d950b817c6.DVI-I-1". See Appendix K, GPU Names For details.