drm/syncobj: Drop add/remove_callback from driver interface

This is used for handling future fences. Currently no driver use
these, and I think given the new timeline fence proposed by KHR it
would be better to have a more abstract interface for future fences.
Could be something simple like a struct dma_future_fence plus a
function to add a callback or wait for the fence to materialize.

Then syncobj (and anything else really) could grow new functions to
expose these two drivers. Normal dma_fence would then keep the nice
guarantee that they will always signal (and through ordering, be
deadlock free). dma_future_fence would then be the tricky one.

This also fixes sphinx complaining about the kerneldoc.

Cc: Jason Ekstrand <jason@jlekstrand.net>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180822092905.19884-1-daniel.vetter@ffwll.ch

drivers/gpu/drm/drm_syncobj.c

@@ -120,14 +120,6 @@ static int drm_syncobj_fence_get_or_add_callback(struct drm_syncobj *syncobj,
 	return ret;
 }
 
-/**
- * drm_syncobj_add_callback - adds a callback to syncobj::cb_list
- * @syncobj: Sync object to which to add the callback
- * @cb: Callback to add
- * @func: Func to use when initializing the drm_syncobj_cb struct
- *
- * This adds a callback to be called next time the fence is replaced
- */
 void drm_syncobj_add_callback(struct drm_syncobj *syncobj,
 			      struct drm_syncobj_cb *cb,
 			      drm_syncobj_func_t func)
@@ -136,21 +128,14 @@ void drm_syncobj_add_callback(struct drm_syncobj *syncobj,
 	drm_syncobj_add_callback_locked(syncobj, cb, func);
 	spin_unlock(&syncobj->lock);
 }
-EXPORT_SYMBOL(drm_syncobj_add_callback);
 
-/**
- * drm_syncobj_add_callback - removes a callback to syncobj::cb_list
- * @syncobj: Sync object from which to remove the callback
- * @cb: Callback to remove
- */
 void drm_syncobj_remove_callback(struct drm_syncobj *syncobj,
 				 struct drm_syncobj_cb *cb)
 {
 	spin_lock(&syncobj->lock);
 	list_del_init(&cb->node);
 	spin_unlock(&syncobj->lock);
 }
-EXPORT_SYMBOL(drm_syncobj_remove_callback);
 
 /**
  * drm_syncobj_replace_fence - replace fence in a sync object.

include/drm/drm_syncobj.h

@@ -131,11 +131,6 @@ drm_syncobj_fence_get(struct drm_syncobj *syncobj)
 
 struct drm_syncobj *drm_syncobj_find(struct drm_file *file_private,
 				     u32 handle);
-void drm_syncobj_add_callback(struct drm_syncobj *syncobj,
-			      struct drm_syncobj_cb *cb,
-			      drm_syncobj_func_t func);
-void drm_syncobj_remove_callback(struct drm_syncobj *syncobj,
-				 struct drm_syncobj_cb *cb);
 void drm_syncobj_replace_fence(struct drm_syncobj *syncobj,
 			       struct dma_fence *fence);
 int drm_syncobj_find_fence(struct drm_file *file_private,