From Funtoo
< Make.conf
Revision as of 00:14, July 28, 2019 by Drobbins (talk | contribs) (DRI vs. Gallium vs. NVIDIA)
Jump to: navigation, search

The VIDEO_CARDS make.conf setting is used to define what graphics support is enabled on your system. This graphics support can include a combination of kernel drivers and user-space libraries that as a whole provide graphics capability for your system. This Portage variable is generally used only by packages that directly implement graphics support, such as media-libs/mesa and a few others. To set VIDEO_CARDS, set it in /etc/make.conf, separating each value with a space, as follows:

   /etc/make.conf (bash source code)
VIDEO_CARDS="intel i965 i915"

Funtoo Differences

Starting with Funtoo Linux 1.4, VIDEO_CARDS settings work a bit differently than in Gentoo and are documented here. Also note that it is possible to have VIDEO_CARDS set for you via use of a Funtoo profile mix-in.

The Funtoo VIDEO_CARDS flags are designed to have a consistent format. If just a graphics driver is listed, such as i965, then it is an X-based DRI driver. Drivers that use the new Gallium driver architecture are in the format gallium-<driver> such as gallium-radeonsi. In addition, any optional framework is listed as a prefix, such as vulkan-i965 for optional DRI-based Vulkan support for i965+ Intel cards.

DRI vs. Gallium vs. NVIDIA

Graphics on Linux can be confusing due to the various technologies involved, not just the different graphics cards available but also the different software architectures for implementing graphics drivers. Traditionally, accelerated graphics in X has been implemented using a combination of technologies:

  • DRI, which stands for Direct Rendering Infrastructure and are user-space libraries that provide accelerated 2D and 3D graphics for X.
  • DRM, the Direct Rendering Manager (Wikipedia) is considered to be a kernel-space component of DRI.
  • Mesa provides an accelerated OpenGL GLX library which leverages DRI and DRM to provide hardware-accelerated graphics.

The most well-supported version of DRI is version 2. There is a dri3 VIDEO_CARDS setting that can be enabled to enable support for version 3 of DRI, which should offer improved performance. DRI version 3 support could be less mature than the same driver with just version 2 support, so the availability of a VIDEO_CARDS option allows it to be turned off if you experience video issues.

More recently, Open Source graphics drivers have started being written using a new architecture called Gallium (not to be confused with Glamour.) Gallium still makes use of the kernel's DRM but provides a more modern way to design graphics drivers. A Gallium-based graphics stack will typically be composed of the following:

  • DRI, which is still used to some extent.
  • DRM, the kernel-space component of the graphics stack.
  • Gallium, a user-space API that exposes the capabilities of the underlying hardware in a more hardware-agnostic way.
  • Mesa's OpenGL GLX library, which leverages Gallium to provide accelerated graphics.

The benefits of Gallium over the 'classic' approach to graphics support is that Gallium allows for user-space graphics libraries like OpenGL to target Gallium itself rather than be written specifically to the architecture of the underlying hardware. This allows for the OpenGL (and other graphics library) implementation to be de-coupled from the underlying hardware while still providing high performance. It's important to note that the benefits of Gallium are primarily focus on the needs of graphics driver developers; in theory, these benefits will result in improved and better-maintained graphics stacks. In other words, just because a driver is Gallium-based doesn't necessarily mean that it will provide you, the user, with superior performance or functionality.

Your graphics driver may use DRI, Gallium or possibly -- in the case of the proprietary NVIDIA driver -- neither!

Understanding What's Available

It is helpful to be aware of the different graphics architectures because there are sometimes multiple implementations of a driver for different graphics driver architectures, and they will each have their own performance characteristics, so a particular one may be better for your needs than others -- the reason why all these competing graphics architectures exist in the first place is to try different approaches to squeeze out the best possible performance from your graphics card.

Let's look at some examples of different graphics driver architectures. For NVIDIA cards there is an Open Source DRI-based driver called nouveau, and an Open Source Gallium-based driver called gallium-nouveau. And in addition, there is also NVIDIA's proprietary accelerated driver simply called nvidia. The nvidia graphics driver typically performs best and supports Vulkan but is closed-source, and sometimes needs to be updated by NVIDIA to support the newest Linux kernels. Some may prefer using nouveau or gallium-nouveau since they are Open Source and always work with the absolute latest upstream Linux kernels.

Some graphics drivers are more mature than others. For example, Intel integrated graphics drivers for DRI have been around a lot longer, are very fast, and are more mature than the equivalent Gallium drivers. And some graphics cards, like modern Radeon cards, only have a Gallium-based driver (gallium-radeonsi). Performance, both with 3D graphics, video playback, and general 2D use is highly dependent on the graphics driver you use so it's good to be aware of what's available for your hardware.

The guiding principle when choosing a graphics stack is -- ask around and also experiment! See which works best for your use case. The Funtoo VIDEO_CARDS system is designed to make this exploration and experimentation as pain-free for users as possible.

Changing VIDEO_CARDS Settings

When changing VIDEO_CARDS settings, either directly by modifying /etc/make.conf or by use of a mix-in, it is important to perform a deep update of your system and ensure that X is configured correctly for your new settings. At the minimum, this generally involves performing an emerge -auDN @world. You will likely notice a rebuild of media-libs/mesa and perhaps x11-libs/libdrm.

Video Acceleration Architectures

In addition to graphics driver architectures, over the years there have been different architectures designed to help accelerate the playback of video. As you might guess, these architectures are different levels of support depending upon the graphics driver selected. The VIDEO_CARDS settings related to graphics drivers are xa, vaapi, vdpau and xvmc. In Funtoo it is safe, and recommended, to append all these settings to your VIDEO_CARDS setting, which can be done by adding this to the end of your /etc/make.conf:

   /etc/make.conf (bash source code)
VIDEO_CARDS="${VIDEO_CARDS} xa vaapi vdpau xvmc"

If you are using the workstation or desktop flavor, these settings will be enabled for you automatically. In addition, you may want to add some or all of these settings to your USE flags to enable any optional video acceleration support in regular software. These VIDEO_CARDS settings enable the support in the underlying graphics driver itself only, if available.

It's also important to note that while most of the time, video acceleration is provided by the underlying graphics driver, this is not the case for Intel integrated graphics, where it is necessary to emerge another ebuild to enable full video acceleration support:

root # emerge libva-intel-driver

Even more confusing, there is a new libva-intel-media-driver which is a new design of the VAAPI-based acceleration for Intel integrated graphics, and requires a bleeding-edge installation of media-libs/libva. This is something that is not yet actively supported under Funtoo but is something that I hope to play with soon.

Use within Ebuilds

Inside ebuilds, the VIDEO_CARDS settings is USE_EXPANDed to a USE flag with a prefix of video_card_. For example, radeonsi will set the video_card_radeonsi USE flag, gallium-osmesa will set the video_card_gallium-osmesa USE flag, etc. Pay careful attention to the use of underscores and hyphens. Hyphens are used in the video card variable name itself, whereas underscores are used in video_card_ only.

Use within Make.conf

Typically, VIDEO_CARDS settings are "stacked", which means that multiple related flags are specified. Here are some common examples:

   /etc/make.conf (bash source code)
# This setting will support nearly all X/DRI-based Intel integrated graphics:
VIDEO_CARDS="intel dri3 i965 i915"

# This next setting is similar to the one above but will also enable Vulkan support:
VIDEO_CARDS="intel dri3 i965 vulkan-i965 i915"

# This next setting will enable Gallium for Intel integrated graphics -- The Intel drivers are currently more mature for X/DRI, though:
VIDEO_CARDS="intel gallium gallium-i915"

# This next setting could be useful if you have hybrid graphics on your laptop and you plan to use X:
VIDEO_CARDS="intel dri3 i965 i915 nvidia"

# This setting would be good for X-based graphics with Radeon cards using gallium:
VIDEO_CARDS="amdgpu radeon gallium gallium-r300 gallium-r600 gallium-radeonsi vulkan-gallium-radeonsi"


The most-common VIDEO_CARDS settings are listed below. For a comprehensive list of settings, type emerge -av mesa and peruse the list of USE flags.

name description platforms
name description platforms
amdgpu AMDGPU is an Open Source graphics driver developed by AMD that supports the latest AMD Radeon graphics cards (GCN 1.2, HD 7xxxx+). It is typically used in conjunction with Mesa's radeonsi driver which provides OpenGL support. There is a kernel-space part and a user-space part (in DRI Gallium X
gallium-i915 This is a gallium-based driver for Intel integrated graphics chipsets, i915 or later. Gallium
gallium-nouveau Open Source NVIDIA Gallium-based graphics driver. Gallium
gallium-osmesa "Osmesa" stands for "off-screen MESA" and allows rendering of graphics into a framebuffer in memory. This supports Gallium-based rendering. Gallium
gallium-r300 A Gallium-based driver for older Radeon cards: R300, R350, RV350, RV380, RS400, RS480, R420, R423, RV410, RS600, RS690, RS740, RV515, R520, RV530, RV560, RV570, R580 Gallium
gallium-r600 A Gallium-based driver for Radeon graphics cards: R600, RV610, RV630, RV620, RV635, RV670, RS780, RS880, RV770, RV730, RV710, RV740, CEDAR, REDWOOD, JUNIPER, CYPRESS, PALM (Wrestler), SUMO, SUMO2, ARUBA, BARTS, TURKS, CAICOS, CAYMAN Gallium
gallium-radeonsi Open Source Radeon driver providing support for modern Radeon graphics (HD5430-HD5970, HDxxx, HD7xxx, R7 cards, R5 230, R9 280 and other R9 cards.) Gallium-based driver. Gallium
gallium-swrast Gallium-based software-only OpenGL driver, also known as "softpipe". This setting will also enable Intel's "swr" driver (taking advantage of some Intel processor instructions for acceleration) on supported CPU architectures. Gallium X
gallium-tegra Open Source NVIDIA driver for Tegra (ARM CPU + Integrated NVIDIA graphics). Gallium-based driver. Gallium
gallium-virgl This driver provides accelerated OpenGL rendering within virtual machines via VirtualGL. Gallium-based driver. Gallium
i915 Enables support for Intel integrated graphics, i915 and more recent chipset. Most modern laptops with Intel integrated graphics will want this enabled. DRI X
i965 Enables support for Intel integrated graphics, i965 and more recent chipset. Most modern laptops with Intel integrated graphics will want this enabled. DRI X
intel Enables general support for Intel integrated graphics. This setting is required when using any Intel-related settings DRI X
nouveau Open Source NVIDIA DRI-based X graphics driver. DRI X
nvidia NVIDIA proprietary accelerated driver support. This driver includes support for traditional X-based accelerated rendering and Vulkan. Although this driver supports X, it does not use the kernel's DRI. Vulkan X
osmesa "Osmesa" stands for "off-screen MESA" and allows rendering of graphics into a framebuffer in memory. This supports X/DRI-based rendering. DRI X
r100 An X/DRI-based driver for older Radeon cards: R100, RV100, RV200, RS100, RS200 DRI X
r200 An X/DRI-based driver for older Radeon cards: R200, RV250, RV280, RS300 DRI X
radeon General support for Radeon cards. This setting is required when using any Radeon-related setting. DRI X
swrast DRI-based driver that does OpenGL without any hardware support. Enabled by default regardless of profile settings, since Mesa needs at least one "real" output to generate libGL. DRI X
virgl This driver provides accelerated OpenGL rendering within virtual machines via VirtualGL. X/DRI-based driver. DRI X
vulkan-amdgpu Enable Vulkan support for AMDGPU. Vulkan
vulkan-intel Enables Mesa's DRI-based Vulkan driver for Intel chipsets. DRI Vulkan