[SOLVED] Mesa: gallium drivers versus dri drivers

The instructions for building mesa in BLFS 9.0 have suddenly become a lot more complicated. There are now configuration flags for both gallium drivers and dri drivers, but i915 (the driver I am most interested in) can only be built as one or the other. I have not been able to find any simple comparison of these options in practice. Can anyone enlighten me?

In previous versions, I used a gallium driver. My computer has an Intel Bay Tree processor with integrated graphics.

When I had intel graphics (an i3), I am fairly certain I built Mesa with the dri drivers and no gallium (-Dgallium-drivers=""). I remember i didn't require LLVM to build Mesa and that worked fine for the i915 driver. I would suggest looking up the Wikipedia page for intel graphics and find your exact CPU/GPU combo and it's capabilities.

Ok, I'll make the dri driver and report back when I get the desktop up.

You apparently need two drivers: i915 and i965. With i915 alone, you get X but no hardware acceleration. glx spits out an error message about not finding i965 and then reports using the software accelerator llvmpipe. So I rebuilt mesa with both drivers and now it seems to work. X reports "intel(0): SNA initialized with Baytrail (gen7) backend" and the "intel(0): [DRI2] DRI driver: i965" And my /dev directory contains a dri subdirectory again.

Baytrail is my cpu, but I know the graphics are somehow integrated into that.

Originally Posted by hazel The instructions for building mesa in BLFS 9.0 have suddenly become a lot more complicated. There are now configuration flags for both gallium drivers and dri drivers, but i915 (the driver I am most interested in) can only be built as one or the other. I have not been able to find any simple comparison of these options in practice. Can anyone enlighten me? In previous versions, I used a gallium driver. My computer has an Intel Bay Tree processor with integrated graphics.

You need to add "iris" to GALLIUM_DRV="i915,nouveau,r600,radeonsi,svga,swrast,virgl" as this is the newest driver code for Intel's platform graphics. IIRC, the DRI code paths are maintenance at this point. (I believe, I don't remember exactly where that was spelled out but this explains how gallium is the future.) Finally, when you have a choice (i915) choose gallium as it is the less complicated code path and is probably where upstream development is concentrated.

Thanks. It looks to me as if gallium is to video drivers what cups is to printers or sane to scanners. It contains all the hardware-independent stuff, leaving just a small hardware driver for the last stage.

How do these drivers relate to the one you install with xorg? The one called xf86-video-whatsit? Obviously both are necessary but how do they divide up the work? Does the mesa driver handle opengl calls and the xorg driver the rest?

xorg use to run an in-kernel driver, which is why you use to need to be a member of the video group. If I understand it correctly, modern xf86-video-xxx drivers (DDX) just provide a wrapper around the DRM/KMS functions in modern kernels and provide the legacy X11 driver interface for xorg-server, as well as things like xrandr.