drm: GEM mmap support

Add core support for mapping of GEM objects.  Drivers should provide a
vm_operations_struct if they want to support page faulting of objects.
The code for handling GEM object offsets was taken from TTM, which was
written by Thomas Hellström.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/drm_vm.c b/drivers/gpu/drm/drm_vm.c
index c234c6f..3ffae02 100644
--- a/drivers/gpu/drm/drm_vm.c
+++ b/drivers/gpu/drm/drm_vm.c
@@ -267,6 +267,9 @@
 				dmah.size = map->size;
 				__drm_pci_free(dev, &dmah);
 				break;
+			case _DRM_GEM:
+				DRM_ERROR("tried to rmmap GEM object\n");
+				break;
 			}
 			drm_free(map, sizeof(*map), DRM_MEM_MAPS);
 		}
@@ -399,7 +402,7 @@
  * Create a new drm_vma_entry structure as the \p vma private data entry and
  * add it to drm_device::vmalist.
  */
-static void drm_vm_open_locked(struct vm_area_struct *vma)
+void drm_vm_open_locked(struct vm_area_struct *vma)
 {
 	struct drm_file *priv = vma->vm_file->private_data;
 	struct drm_device *dev = priv->minor->dev;
@@ -540,7 +543,7 @@
  * according to the mapping type and remaps the pages. Finally sets the file
  * pointer and calls vm_open().
  */
-static int drm_mmap_locked(struct file *filp, struct vm_area_struct *vma)
+int drm_mmap_locked(struct file *filp, struct vm_area_struct *vma)
 {
 	struct drm_file *priv = filp->private_data;
 	struct drm_device *dev = priv->minor->dev;