You can't document function pointer member as functions.
drivers/gpu/drm/i915/gem/i915_gem_region.h:25: warning: Incorrect use of kernel-doc format: * process_obj - Process the current object
drivers/gpu/drm/i915/gem/i915_gem_region.h:35: warning: Function parameter or member 'process_obj' not described in 'i915_gem_apply_to_region_ops'