fix: Clarify the graphics and display driver capabilities

[ehfd]

Reviewer: @cdesiniotis @henry118

Please feel free to edit my branch as required.

Summary

The driver capability table describes graphics as "Required for running OpenGL, EGL, and Vulkan applications" and display as "required for leveraging X11 display." A user with a Vulkan or OpenGL application that displays its output follows that to graphics alone and ends up with a driver that cannot present.

Changes

• graphics — required for rendering OpenGL, EGL, and Vulkan applications.
• display — required for displaying X11 or Wayland windows; implies graphics.
• A short note that NVIDIA_DRIVER_CAPABILITIES replaces the default capabilities rather than adding to them, with compute,graphics,display as the example.
• compute and graphics began their descriptions with a capital Required while the other four rows did not; all six now match.

Why

Measured on NVIDIA Container Toolkit and libnvidia-container 1.20.0, driver 580.178.04, 2x Tesla P100, against an NVIDIA-driven X server, with the capability string as the only variable between runs:

compute,graphics          no /dev/nvidia-modeset
                          vkGetPhysicalDeviceSurfacePresentModesKHR  VkResult=-13

compute,graphics,display  /dev/nvidia-modeset present
                          vkGetPhysicalDeviceSurfacePresentModesKHR  VkResult=0
                          vkCreateSwapchainKHR                       VkResult=0

Two things follow that the page does not say today:

1. graphics is not sufficient for an application that displays its output. display supplies /dev/nvidia-modeset, which the NVIDIA client driver needs for its window-system integration. This is not X11-specific — the same applies to Wayland and to off-screen surfaces where no X server is involved, so describing display as being for X11 is incomplete.

2. Because the variable replaces the default set rather than extending it, graphics,display on its own silently drops compute and the application fails to start at all. The value that works is compute,graphics,display.

Related

• fix: Create NVIDIA control device nodes in nvidia-cdi-refresh.service nvidia-container-toolkit#1979 and fix: NVIDIA X.Org driver modules mount fixes nvidia-container-toolkit#1980 (merged) — the device node and graphics configuration halves of this work.
• fix: Discover /dev/nvidia-modeset instead of assuming it exists libnvidia-container#388 — discussion of the graphics / display boundary that this wording settles on the documentation side.

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