softpipe : a software rasterizer and a reference Gallium driver.d3d12 : for OpenGL 3.3 support on devices that only support D3D12 (i.e.zink : a Gallium driver used to run OpenGL on top of Vulkan.iris : for Intel's Gen 8 hardware and later.
There are two Mesa packages, each with a distinct set of drivers:
Mesa also provides software rasterizers, such as llvmpipe. It has a collection of open-source drivers for Intel graphics, AMD (formerly ATI) and NVIDIA GPUs. Mesa is an open-source OpenGL implementation, continually updated to support the latest OpenGL specification.
