root@x260 ~# equery u mesa
[ Legend : U - final flag setting for installation]
[        : I - package is installed with flag     ]
[ Colors : set, unset                             ]
 * Found these USE flags for media-libs/mesa-17.2.0_rc4:
 U I
 + - abi_x86_32           : 32-bit (x86) libraries
 - - bindist              : Disable patent-encumbered ARB_texture_float, EXT_texture_shared_exponent, and EXT_packed_float extensions.
 + - classic              : Build drivers based on the classic architecture.
 - - d3d9                 : Enable Direct 3D9 API through Nine state tracker. Can be used together with patched wine.
 - - debug                : Enable extra debug codepaths, like asserts and extra output. If you want to get meaningful backtraces see
                            https://wiki.gentoo.org/wiki/Project:Quality_Assurance/Backtraces
 + + dri3                 : Enable DRI3 support.
 + - egl                  : Enable EGL support.
 + - gallium              : Build drivers based on Gallium3D, the new architecture for 3D graphics drivers.
 + - gbm                  : Enable the Graphics Buffer Manager for EGL on KMS.
 - - gles1                : Enable GLESv1 support.
 - - gles2                : Enable GLESv2 support.
 + - llvm                 : Enable LLVM backend for Gallium3D.
 + + nptl                 : Enable support for Native POSIX Threads Library, the new threading module (requires linux-2.6 or better usually)
 - - opencl               : Enable the Clover Gallium OpenCL state tracker.
 - - openmax              : Enable OpenMAX video decode/encode acceleration for Gallium3D.
 - - osmesa               : Build the Mesa library for off-screen rendering.
 - - pax_kernel           : Enable if the user plans to run the package under a pax enabled hardened kernel
 - - pic                  : disable optimized assembly code that is not PIC friendly
 - - unwind               : Add support for stack trace unwinding and function name resolution
 - - vaapi                : Enable Video Acceleration API for hardware decoding
 - - valgrind             : Compile in valgrind memory hints
 - - vdpau                : Enable the VDPAU acceleration interface for the Gallium3D Video Layer.
 - - video_cards_i915     : VIDEO_CARDS setting to build driver for Intel i915 video cards
 - - video_cards_i965     : VIDEO_CARDS setting to build driver for Intel i965 video cards
 - - video_cards_imx      : VIDEO_CARDS setting to build driver for Freescale i.MX video cards
 + + video_cards_intel    : VIDEO_CARDS setting to build driver for Intel video cards
 - - video_cards_nouveau  : VIDEO_CARDS setting to build reverse-engineered driver for nvidia cards
 - - video_cards_r100     : VIDEO_CARDS setting to build only r100 based chips code for radeon
 - - video_cards_r200     : VIDEO_CARDS setting to build only r200 based chips code for radeon
 - - video_cards_r300     : VIDEO_CARDS setting to build only r300, r400 and r500 based chips code for radeon
 - - video_cards_r600     : VIDEO_CARDS setting to build only r600, r700, Evergreen and Northern Islands based chips code for radeon
 - - video_cards_radeon   : VIDEO_CARDS setting to build driver for ATI radeon video cards
 - - video_cards_radeonsi : VIDEO_CARDS setting to build only Southern Islands based chips code for radeon
 - - video_cards_vmware   : VIDEO_CARDS setting to build driver for vmware video cards
 - - vulkan               : Enable Vulkan drivers
 + - wayland              : Enable support for dev-libs/wayland
 - - xa                   : Enable the XA (X Acceleration) API for Gallium3D.
 - - xvmc                 : Enable the XvMC acceleration interface for the Gallium3D Video Layer.
root@x260 ~#