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, 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.

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.