drm: Return error codes from struct drm_driver.gem_create_object

GEM helper libraries use struct drm_driver.gem_create_object to let
drivers override GEM object allocation. On failure, the call returns
NULL.

Change the semantics to make the calls return a pointer-encoded error.
This aligns the callback with its callers. Fixes the ingenic driver,
which already returns an error pointer.

Also update the callers to handle the involved types more strictly.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Steven Price <steven.price@arm.com>
Acked-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20211130095255.26710-1-tzimmermann@suse.de

1 files changed, 10 insertions, 7 deletions

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 0eeda1012364..7915047cb041 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -56,14 +56,17 @@ __drm_gem_shmem_create(struct drm_device *dev, size_t size, bool private)
 
 	size = PAGE_ALIGN(size);
 
-	if (dev->driver->gem_create_object)
+	if (dev->driver->gem_create_object) {
 		obj = dev->driver->gem_create_object(dev, size);
-	else
-		obj = kzalloc(sizeof(*shmem), GFP_KERNEL);
-	if (!obj)
-		return ERR_PTR(-ENOMEM);
-
-	shmem = to_drm_gem_shmem_obj(obj);
+		if (IS_ERR(obj))
+			return ERR_CAST(obj);
+		shmem = to_drm_gem_shmem_obj(obj);
+	} else {
+		shmem = kzalloc(sizeof(*shmem), GFP_KERNEL);
+		if (!shmem)
+			return ERR_PTR(-ENOMEM);
+		obj = &shmem->base;
+	}
 
 	if (!obj->funcs)
 		obj->funcs = &drm_gem_shmem_funcs;