drm/gem: add support for private objects

These small changes should allow GEM to be used with non shmem objects as
well as shmem objects. In the GMA500 case it allows the base framebuffer to
appear as a GEM object and thus acquire a handle and work with KMS.

For i915 it ought to be trivial to get back the wasted memory but putting the
system fb back into stolen RAM and in general I can imagine it allowing the
use of GEM and thus KMS with all the older cards that have their framebuffer
firmly placed in video RAM.
Signed-off-by: Alan Cox <alan@linux.intel.com>
Tested-by: Rob Clark <rob@ti.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_gem.c

@@ -129,7 +129,7 @@ drm_gem_destroy(struct drm_device *dev)
 }
 
 /**
- * Initialize an already allocate GEM object of the specified size with
+ * Initialize an already allocated GEM object of the specified size with
  * shmfs backing store.
  */
 int drm_gem_object_init(struct drm_device *dev,
@@ -150,6 +150,27 @@ int drm_gem_object_init(struct drm_device *dev,
 }
 EXPORT_SYMBOL(drm_gem_object_init);
 
+/**
+ * Initialize an already allocated GEM object of the specified size with
+ * no GEM provided backing store. Instead the caller is responsible for
+ * backing the object and handling it.
+ */
+int drm_gem_private_object_init(struct drm_device *dev,
+			struct drm_gem_object *obj, size_t size)
+{
+	BUG_ON((size & (PAGE_SIZE - 1)) != 0);
+
+	obj->dev = dev;
+	obj->filp = NULL;
+
+	kref_init(&obj->refcount);
+	atomic_set(&obj->handle_count, 0);
+	obj->size = size;
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_gem_private_object_init);
+
 /**
  * Allocate a GEM object of the specified size with shmfs backing store
  */
@@ -444,6 +465,7 @@ drm_gem_release(struct drm_device *dev, struct drm_file *file_private)
 void
 drm_gem_object_release(struct drm_gem_object *obj)
 {
+	if (obj->filp)
 	    fput(obj->filp);
 }
 EXPORT_SYMBOL(drm_gem_object_release);

include/drm/drmP.h

@@ -1541,6 +1541,8 @@ struct drm_gem_object *drm_gem_object_alloc(struct drm_device *dev,
 					    size_t size);
 int drm_gem_object_init(struct drm_device *dev,
 			struct drm_gem_object *obj, size_t size);
+int drm_gem_private_object_init(struct drm_device *dev,
+			struct drm_gem_object *obj, size_t size);
 void drm_gem_object_handle_free(struct drm_gem_object *obj);
 void drm_gem_vm_open(struct vm_area_struct *vma);
 void drm_gem_vm_close(struct vm_area_struct *vma);