i915: add dmabuf/prime buffer sharing support.

This adds handle->fd and fd->handle support to i915, this is to allow
for offloading of rendering in one direction and outputs in the other.

v2 from Daniel Vetter:
- fixup conflicts with the prepare/finish gtt prep work.
- implement ppgtt binding support.

Note that we have squat i-g-t testcoverage for any of the lifetime and
access rules dma_buf/prime support brings along. And there are quite a
few intricate situations here.

Also note that the integration with the existing code is a bit
hackish, especially around get_gtt_pages and put_gtt_pages. It imo
would be easier with the prep code from Chris Wilson's unbound series,
but that is for 3.6.

Also note that I didn't bother to put the new prepare/finish gtt hooks
to good use by moving the dma_buf_map/unmap_attachment calls in there
(like we've originally planned for).

Last but not least this patch is only compile-tested, but I've changed
very little compared to Dave Airlie's version. So there's a decent
chance v2 on drm-next works as well as v1 on 3.4-rc.

v3: Right when I've hit sent I've noticed that I've screwed up one
obj->sg_list (for dmar support) and obj->sg_table (for prime support)
disdinction. We should be able to merge these 2 paths, but that's
material for another patch.

v4: fix the error reporting bugs pointed out by ickle.

v5: fix another error, and stop non-gtt mmaps on shared objects
stop pread/pwrite on imported objects, add fake kmap

Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 11c7a6a..377c21f 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -940,6 +940,8 @@
 	struct scatterlist *sg_list;
 	int num_sg;
 
+	/* prime dma-buf support */
+	struct sg_table *sg_table;
 	/**
 	 * Used for performing relocations during execbuffer insertion.
 	 */
@@ -1245,6 +1247,8 @@
 void i915_gem_release_mmap(struct drm_i915_gem_object *obj);
 void i915_gem_lastclose(struct drm_device *dev);
 
+int i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj,
+				  gfp_t gfpmask);
 int __must_check i915_mutex_lock_interruptible(struct drm_device *dev);
 int __must_check i915_gem_object_wait_rendering(struct drm_i915_gem_object *obj);
 int i915_gem_object_sync(struct drm_i915_gem_object *obj,
@@ -1342,6 +1346,13 @@
 int i915_gem_object_set_cache_level(struct drm_i915_gem_object *obj,
 				    enum i915_cache_level cache_level);
 
+struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
+				struct dma_buf *dma_buf);
+
+struct dma_buf *i915_gem_prime_export(struct drm_device *dev,
+				struct drm_gem_object *gem_obj, int flags);
+
+
 /* i915_gem_gtt.c */
 int __must_check i915_gem_init_aliasing_ppgtt(struct drm_device *dev);
 void i915_gem_cleanup_aliasing_ppgtt(struct drm_device *dev);