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

drivers/gpu/drm/drm_gem_cma_helper.c

@@ -67,18 +67,21 @@ __drm_gem_cma_create(struct drm_device *drm, size_t size, bool private)
 	struct drm_gem_object *gem_obj;
 	int ret = 0;
 
-	if (drm->driver->gem_create_object)
+	if (drm->driver->gem_create_object) {
 		gem_obj = drm->driver->gem_create_object(drm, size);
-	else
-		gem_obj = kzalloc(sizeof(*cma_obj), GFP_KERNEL);
-	if (!gem_obj)
+		if (IS_ERR(gem_obj))
+			return ERR_CAST(gem_obj);
+		cma_obj = to_drm_gem_cma_obj(gem_obj);
+	} else {
+		cma_obj = kzalloc(sizeof(*cma_obj), GFP_KERNEL);
+		if (!cma_obj)
 			return ERR_PTR(-ENOMEM);
+		gem_obj = &cma_obj->base;
+	}
 
 	if (!gem_obj->funcs)
 		gem_obj->funcs = &drm_gem_cma_default_funcs;
 
-	cma_obj = container_of(gem_obj, struct drm_gem_cma_object, base);
-
 	if (private) {
 		drm_gem_private_object_init(drm, gem_obj, size);
 

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);
-
+		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;

drivers/gpu/drm/drm_gem_vram_helper.c

@@ -197,8 +197,8 @@ struct drm_gem_vram_object *drm_gem_vram_create(struct drm_device *dev,
 
 	if (dev->driver->gem_create_object) {
 		gem = dev->driver->gem_create_object(dev, size);
-		if (!gem)
-			return ERR_PTR(-ENOMEM);
+		if (IS_ERR(gem))
+			return ERR_CAST(gem);
 		gbo = drm_gem_vram_of_gem(gem);
 	} else {
 		gbo = kzalloc(sizeof(*gbo), GFP_KERNEL);

drivers/gpu/drm/lima/lima_gem.c

@@ -221,7 +221,7 @@ struct drm_gem_object *lima_gem_create_object(struct drm_device *dev, size_t siz
 
 	bo = kzalloc(sizeof(*bo), GFP_KERNEL);
 	if (!bo)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	mutex_init(&bo->lock);
 	INIT_LIST_HEAD(&bo->va);

drivers/gpu/drm/panfrost/panfrost_gem.c

@@ -223,7 +223,7 @@ struct drm_gem_object *panfrost_gem_create_object(struct drm_device *dev, size_t
 
 	obj = kzalloc(sizeof(*obj), GFP_KERNEL);
 	if (!obj)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	INIT_LIST_HEAD(&obj->mappings.list);
 	mutex_init(&obj->mappings.lock);

drivers/gpu/drm/v3d/v3d_bo.c

@@ -70,11 +70,11 @@ struct drm_gem_object *v3d_create_object(struct drm_device *dev, size_t size)
 	struct drm_gem_object *obj;
 
 	if (size == 0)
-		return NULL;
+		return ERR_PTR(-EINVAL);
 
 	bo = kzalloc(sizeof(*bo), GFP_KERNEL);
 	if (!bo)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 	obj = &bo->base.base;
 
 	obj->funcs = &v3d_gem_funcs;

drivers/gpu/drm/vgem/vgem_drv.c

@@ -97,7 +97,7 @@ static struct drm_gem_object *vgem_gem_create_object(struct drm_device *dev, siz
 
 	obj = kzalloc(sizeof(*obj), GFP_KERNEL);
 	if (!obj)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	/*
 	 * vgem doesn't have any begin/end cpu access ioctls, therefore must use

drivers/gpu/drm/virtio/virtgpu_object.c

@@ -139,7 +139,7 @@ struct drm_gem_object *virtio_gpu_create_object(struct drm_device *dev,
 
 	shmem = kzalloc(sizeof(*shmem), GFP_KERNEL);
 	if (!shmem)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	dshmem = &shmem->base.base;
 	dshmem->base.funcs = &virtio_gpu_shmem_funcs;

include/drm/drm_drv.h

@@ -291,8 +291,9 @@ struct drm_driver {
 	/**
 	 * @gem_create_object: constructor for gem objects
 	 *
-	 * Hook for allocating the GEM object struct, for use by the CMA and
-	 * SHMEM GEM helpers.
+	 * Hook for allocating the GEM object struct, for use by the CMA
+	 * and SHMEM GEM helpers. Returns a GEM object on success, or an
+	 * ERR_PTR()-encoded error code otherwise.
 	 */
 	struct drm_gem_object *(*gem_create_object)(struct drm_device *dev,
 						    size_t size);