I don't have the hardware to test compilation of everything that depends on this change in a reasonable amount of time, but I did build and test KDE on top of it.

I don't think recompiling reverse dependencies is worth checking. Running with the 19.3.5 driver on various GPU seems much more worthwhile (even if running SW were compiled against 19.3.3). There's actually precedent that in the past such patch bump in mesa caused too many problems on a nixos stable release and it had to be reverted.

Thank you for your reply, and sorry for the slow turn around. I got wrapped around the axle on something like #85866 while trying to find test assets.

Running with the 19.3.5 driver on various GPU seems much more worthwhile

This makes sense to me. I'm running this now on:

• amdgpu on Vega 8
• modesetting on Ivybridge, Skylake

How many/what kinds of GPUs would give you confidence for merging? Are there any particular tests you would suggest?

(even if running SW were compiled against 19.3.3).

Is there a way to do that? I guess you could manually edit the nix store; I've never tried that. It's taking me over a day to build a desktop with this, if there's a better way I'm all ears.

There's actually precedent that in the past such patch bump in mesa caused too many problems on a nixos stable release and it had to be reverted.

I seem to be the only person with a problem on 19.3.3. If you think this is too risky for the payoff, I would respect that.

Here's how I'd switch drivers in NixOS config:

{
  imports = [ # you'd typically add this part next to your other imports
    
    (let mkDrivers = pkgs: (pkgs.mesa.overrideAttrs (a_: rec {
          branch = "19.3";
          version = "${branch}.5";
          src = pkgs.fetchurl {
            urls = [
              "ftp://ftp.freedesktop.org/pub/mesa/mesa-${version}.tar.xz"
              "ftp://ftp.freedesktop.org/pub/mesa/${version}/mesa-${version}.tar.xz"
              "ftp://ftp.freedesktop.org/pub/mesa/older-versions/${branch}.x/${version}/mesa-${version}.tar.xz"
              "https://mesa.freedesktop.org/archive/mesa-${version}.tar.xz"
            ];
            sha256 = "1dn6975sj25kx6a6x5054ql27lqlshkp5m8cg8nwhwdranq9b600";
          };
        })).drivers;
      in { pkgs, ... }: {
        hardware.opengl = {
          package = mkDrivers pkgs;
          package32 = mkDrivers pkgs.pkgsi686Linux;
        };
      }
    )

  ];
}

This should only rebuild one or two mesas, nothing else – depending on whether you use 32-bit OpenGL.

EDIT: when you nixos-rebuild switch, systemd will immediately switch the symlinks, but I expect most applications will need to get restarted to use the different OpenGL.