Mesa EGL platform Mir does not implement environment variable LIBGL_ALWAYS_SOFTWARE

[Daniel van Vugt]

Mir binaries ignore Mesa setting LIBGL_ALWAYS_SOFTWARE=1 and only ever try hardware acceleration.

See: http://mesa3d.org/envvars.html

[Daniel van Vugt (vanvugt)]

A quick grep seems to suggest it's the responsibility of each EGL platform to re-implement the environment check:

$ grep -r LIBGL_ALWAYS_SOFT src
src/glx/glxext.c: glx_accel = (getenv("LIBGL_ALWAYS_SOFTWARE") == NULL);
src/glx/apple/apple_visual.c: else if (getenv("LIBGL_ALWAYS_SOFTWARE") != NULL) {
src/egl/drivers/dri2/platform_wayland.c: int hw_accel = (getenv("LIBGL_ALWAYS_SOFTWARE") == NULL);
src/egl/drivers/dri2/platform_x11.c: int x11_dri2_accel = (getenv("LIBGL_ALWAYS_SOFTWARE") == NULL);

[Daniel van Vugt (vanvugt)]

Accidentally found a workaround!

You can set environment GBM_ALWAYS_SOFTWARE=1 for Mir servers and clients, and they will then successfully render in software using LLVMpipe.

[Daniel van Vugt (vanvugt)]

Note that GBM_ALWAYS_SOFTWARE=1 is not a solution, because using GBM buffers for software rendering seems to be a massive bottleneck -> bug 1576032

[Cemil Azizoglu (cemil-azizoglu)]

I took a look at implementing LIBGL_ALWAYS_SOFTWARE=1, and it shouldn't be that difficult to do. You're right it will need to go in platform-mir. Only thing missing is a good motivation, or use-case to implement this.

[Michał Sawicz (saviq)]

Syncing task from Mir.

[Timo Aaltonen (tjaalton)]

Mir EGL platform is gone