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LFS is a project that provides you with the steps necessary to build your own custom Linux system.

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Old 09-11-2019, 05:31 AM   #1
hazel
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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.
 
Old 09-11-2019, 09:07 AM   #2
bryan_S
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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.
 
Old 09-11-2019, 10:58 AM   #3
hazel
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Ok, I'll make the dri driver and report back when I get the desktop up.

Last edited by hazel; 09-11-2019 at 11:05 AM.
 
Old 09-13-2019, 05:53 AM   #4
hazel
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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.
 
Old 09-16-2019, 09:37 PM   #5
Luridis
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Quote:
Originally Posted by hazel View Post
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.
 
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Old 09-17-2019, 06:20 AM   #6
hazel
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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?
 
Old 09-17-2019, 08:25 AM   #7
Luridis
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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.
 
  


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