mmap
Provide which gem object you wish to map in offset.
To get the offset use AMDGPU_GEM_MMAP
The object might not be mappable.
Once the right object is fount it's mmap function is called.
See amdgpu_gem_object_mmap() in kernel/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c.
Remember gem objects are reference counted.