src/drm-shim/README.md


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    Contents⊕
  
  
  DRM
  shim - Fake GEM kernel drivers in userspace for CI
  
  Limitations
  Using
  
  
DRM shim
- Fake GEM kernel drivers in userspace for CI
On CI systems where we don't control the kernel, it would be nice to
be able to present either no-op GEM devices (for shader-db runs) or
simulator-backed GEM devices (for testing against a software simulator
or FPGA). This lets us do that by intercepting libc calls and exposing
render nodes.
Limitations

Doesn't know how to handle DRM fds getting passed over the wire from
X11 (Could we use kmsro to support the X11 case?).
libc interception is rather glibc-specific and fragile.
Can easily break gdb if the libc interceptor code is what's broken.
(ulimit -c unlimited and doing gdb on the core after the fact can
help)

Using
You choose the backend by setting LD_PRELOAD to the shim
you want. Since this will effectively fake another DRM device to your
system, you may need some work on your userspace to get your test
application to use it if it's not the only DRM device present. Setting
DRM_SHIM_DEBUG=1 in the environment will print out what
path the shim initialized on.
For piglit tests, you can set:
PIGLIT_PLATFORM=gbm
WAFFLE_GBM_DEVICE=<path from DRM_SHIM_DEBUG>
See your drm-shim backend's README for details on how to use it.