drm/udl: Allocate GEM object via struct drm_driver.gem_create_object

In preparation of a switch to SHMEM, udl now allocates its GEM
objects via struct drm_driver.gem_create_object. No functional
changes are made.

For SHMEM GEM objects, udl will require the use of a special mmap
function, which we set though the create-object function.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191107094307.19870-3-tzimmermann@suse.de

drivers/gpu/drm/udl/udl_drv.c

@@ -64,6 +64,7 @@ static struct drm_driver driver = {
 
 	/* gem hooks */
 	.gem_free_object_unlocked = udl_gem_free_object,
+	.gem_create_object = udl_driver_gem_create_object,
 	.gem_vm_ops = &udl_gem_vm_ops,
 
 	.dumb_create = udl_dumb_create,

drivers/gpu/drm/udl/udl_drv.h

@@ -125,6 +125,8 @@ int udl_dumb_create(struct drm_file *file_priv,
 int udl_gem_mmap(struct drm_file *file_priv, struct drm_device *dev,
 		 uint32_t handle, uint64_t *offset);
 
+struct drm_gem_object *udl_driver_gem_create_object(struct drm_device *dev,
+						    size_t size);
 void udl_gem_free_object(struct drm_gem_object *gem_obj);
 struct udl_gem_object *udl_gem_alloc_object(struct drm_device *dev,
 					    size_t size);

drivers/gpu/drm/udl/udl_gem.c

@@ -6,26 +6,43 @@
 #include <linux/dma-buf.h>
 #include <linux/vmalloc.h>
 
+#include <drm/drm_drv.h>
 #include <drm/drm_mode.h>
 #include <drm/drm_prime.h>
 
 #include "udl_drv.h"
 
-struct udl_gem_object *udl_gem_alloc_object(struct drm_device *dev,
-					    size_t size)
+/*
+ * Helpers for struct drm_driver
+ */
+
+struct drm_gem_object *udl_driver_gem_create_object(struct drm_device *dev,
+						    size_t size)
 {
 	struct udl_gem_object *obj;
 
 	obj = kzalloc(sizeof(*obj), GFP_KERNEL);
+	if (!obj)
+		return NULL;
+
+	return &obj->base;
+}
+
+struct udl_gem_object *udl_gem_alloc_object(struct drm_device *dev,
+					    size_t size)
+{
+	struct drm_gem_object *obj;
+
+	obj = dev->driver->gem_create_object(dev, size);
 	if (obj == NULL)
 		return NULL;
 
-	if (drm_gem_object_init(dev, &obj->base, size) != 0) {
+	if (drm_gem_object_init(dev, obj, size) != 0) {
 		kfree(obj);
 		return NULL;
 	}
 
-	return obj;
+	return to_udl_bo(obj);
 }
 
 static int