drm/cma-helper: Pass GEM CMA object in public interfaces

Change all GEM CMA object functions that receive a GEM object
of type struct drm_gem_object to expect an object of type
struct drm_gem_cma_object instead.

This change reduces the number of upcasts from struct drm_gem_object
by moving them into callers. The C compiler can now verify that the
GEM CMA functions are called with the correct type.

For consistency, the patch also renames drm_gem_cma_free_object to
drm_gem_cma_free. It further updates documentation for a number of
functions.

Signed-off-by: Thomas Zimmermann <[e-mail]>
Reviewed-by: Maxime Ripard <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/drm_gem_cma_helper.c

···
  * The DRM GEM/CMA helpers use this allocator as a means to provide buffer
  * objects that are physically contiguous in memory. This is useful for
  * display drivers that are unable to map scattered buffers via an IOMMU.
+ *
+ * For GEM callback helpers in struct &drm_gem_object functions, see likewise
+ * named functions with an _object_ infix (e.g., drm_gem_cma_object_vmap() wraps
+ * drm_gem_cma_vmap()). These helpers perform the necessary type conversion.
  */
 
 static const struct drm_gem_object_funcs drm_gem_cma_default_funcs = {
···
 }
 
 /**
- * drm_gem_cma_free_object - free resources associated with a CMA GEM object
- * @gem_obj: GEM object to free
+ * drm_gem_cma_free - free resources associated with a CMA GEM object
+ * @cma_obj: CMA GEM object to free
  *
  * This function frees the backing memory of the CMA GEM object, cleans up the
  * GEM object state and frees the memory used to store the object itself.
  * If the buffer is imported and the virtual address is set, it is released.
  */
-void drm_gem_cma_free_object(struct drm_gem_object *gem_obj)
+void drm_gem_cma_free(struct drm_gem_cma_object *cma_obj)
 {
-	struct drm_gem_cma_object *cma_obj = to_drm_gem_cma_obj(gem_obj);
+	struct drm_gem_object *gem_obj = &cma_obj->base;
 	struct dma_buf_map map = DMA_BUF_MAP_INIT_VADDR(cma_obj->vaddr);
 
 	if (gem_obj->import_attach) {
···
 
 	kfree(cma_obj);
 }
-EXPORT_SYMBOL_GPL(drm_gem_cma_free_object);
+EXPORT_SYMBOL_GPL(drm_gem_cma_free);
 
 /**
  * drm_gem_cma_dumb_create_internal - create a dumb buffer object
···
 
 /**
  * drm_gem_cma_print_info() - Print &drm_gem_cma_object info for debugfs
+ * @cma_obj: CMA GEM object
  * @p: DRM printer
  * @indent: Tab indentation level
- * @obj: GEM object
  *
- * This function can be used as the &drm_driver->gem_print_info callback.
- * It prints paddr and vaddr for use in e.g. debugfs output.
+ * This function prints paddr and vaddr for use in e.g. debugfs output.
  */
-void drm_gem_cma_print_info(struct drm_printer *p, unsigned int indent,
-			    const struct drm_gem_object *obj)
+void drm_gem_cma_print_info(const struct drm_gem_cma_object *cma_obj,
+			    struct drm_printer *p, unsigned int indent)
 {
-	const struct drm_gem_cma_object *cma_obj = to_drm_gem_cma_obj(obj);
-
 	drm_printf_indent(p, indent, "paddr=%pad\n", &cma_obj->paddr);
 	drm_printf_indent(p, indent, "vaddr=%p\n", cma_obj->vaddr);
 }
···
 /**
  * drm_gem_cma_get_sg_table - provide a scatter/gather table of pinned
  *     pages for a CMA GEM object
- * @obj: GEM object
+ * @cma_obj: CMA GEM object
  *
  * This function exports a scatter/gather table by calling the standard
  * DMA mapping API.
···
  * Returns:
  * A pointer to the scatter/gather table of pinned pages or NULL on failure.
  */
-struct sg_table *drm_gem_cma_get_sg_table(struct drm_gem_object *obj)
+struct sg_table *drm_gem_cma_get_sg_table(struct drm_gem_cma_object *cma_obj)
 {
-	struct drm_gem_cma_object *cma_obj = to_drm_gem_cma_obj(obj);
+	struct drm_gem_object *obj = &cma_obj->base;
 	struct sg_table *sgt;
 	int ret;
 
···
 /**
  * drm_gem_cma_vmap - map a CMA GEM object into the kernel's virtual
  *     address space
- * @obj: GEM object
+ * @cma_obj: CMA GEM object
  * @map: Returns the kernel virtual address of the CMA GEM object's backing
  *       store.
  *
- * This function maps a buffer into the kernel's
- * virtual address space. Since the CMA buffers are already mapped into the
- * kernel virtual address space this simply returns the cached virtual
- * address.
+ * This function maps a buffer into the kernel's virtual address space.
+ * Since the CMA buffers are already mapped into the kernel virtual address
+ * space this simply returns the cached virtual address.
  *
  * Returns:
  * 0 on success, or a negative error code otherwise.
  */
-int drm_gem_cma_vmap(struct drm_gem_object *obj, struct dma_buf_map *map)
+int drm_gem_cma_vmap(struct drm_gem_cma_object *cma_obj, struct dma_buf_map *map)
 {
-	struct drm_gem_cma_object *cma_obj = to_drm_gem_cma_obj(obj);
-
 	dma_buf_map_set_vaddr(map, cma_obj->vaddr);
 
 	return 0;
···
 
 /**
  * drm_gem_cma_mmap - memory-map an exported CMA GEM object
- * @obj: GEM object
+ * @cma_obj: CMA GEM object
  * @vma: VMA for the area to be mapped
  *
  * This function maps a buffer into a userspace process's address space.
···
  * Returns:
  * 0 on success or a negative error code on failure.
  */
-int drm_gem_cma_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
+int drm_gem_cma_mmap(struct drm_gem_cma_object *cma_obj, struct vm_area_struct *vma)
 {
-	struct drm_gem_cma_object *cma_obj;
+	struct drm_gem_object *obj = &cma_obj->base;
 	int ret;
 
 	/*
···
 	 */
 	vma->vm_pgoff -= drm_vma_node_start(&obj->vma_node);
 	vma->vm_flags &= ~VM_PFNMAP;
-
-	cma_obj = to_drm_gem_cma_obj(obj);
 
 	if (cma_obj->map_noncoherent) {
 		vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);

drivers/gpu/drm/vc4/vc4_bo.c

···
 		bo->validated_shader = NULL;
 	}
 
-	drm_gem_cma_free_object(obj);
+	drm_gem_cma_free(&bo->base);
 }
 
 static void vc4_bo_remove_from_cache(struct vc4_bo *bo)
···
 		return -EINVAL;
 	}
 
-	return drm_gem_cma_mmap(obj, vma);
+	return drm_gem_cma_mmap(&bo->base, vma);
 }
 
 static const struct vm_operations_struct vc4_vm_ops = {

include/drm/drm_gem_cma_helper.h

···
 #define to_drm_gem_cma_obj(gem_obj) \
 	container_of(gem_obj, struct drm_gem_cma_object, base)
 
-/* free GEM object */
-void drm_gem_cma_free_object(struct drm_gem_object *gem_obj);
-
-/* allocate physical memory */
 struct drm_gem_cma_object *drm_gem_cma_create(struct drm_device *drm,
 					      size_t size);
+void drm_gem_cma_free(struct drm_gem_cma_object *cma_obj);
+void drm_gem_cma_print_info(const struct drm_gem_cma_object *cma_obj,
+			    struct drm_printer *p, unsigned int indent);
+struct sg_table *drm_gem_cma_get_sg_table(struct drm_gem_cma_object *cma_obj);
+int drm_gem_cma_vmap(struct drm_gem_cma_object *cma_obj, struct dma_buf_map *map);
+int drm_gem_cma_mmap(struct drm_gem_cma_object *cma_obj, struct vm_area_struct *vma);
 
 extern const struct vm_operations_struct drm_gem_cma_vm_ops;
-
-void drm_gem_cma_print_info(struct drm_printer *p, unsigned int indent,
-			    const struct drm_gem_object *obj);
-
-struct sg_table *drm_gem_cma_get_sg_table(struct drm_gem_object *obj);
-int drm_gem_cma_vmap(struct drm_gem_object *obj, struct dma_buf_map *map);
-int drm_gem_cma_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma);
 
 /*
  * GEM object functions
  */
 
 /**
- * drm_gem_cma_object_free - GEM object function for drm_gem_cma_free_object()
+ * drm_gem_cma_object_free - GEM object function for drm_gem_cma_free()
  * @obj: GEM object to free
  *
  * This function wraps drm_gem_cma_free_object(). Drivers that employ the CMA helpers
···
  */
 static inline void drm_gem_cma_object_free(struct drm_gem_object *obj)
 {
-	drm_gem_cma_free_object(obj);
+	struct drm_gem_cma_object *cma_obj = to_drm_gem_cma_obj(obj);
+
+	drm_gem_cma_free(cma_obj);
 }
 
 /**
···
 static inline void drm_gem_cma_object_print_info(struct drm_printer *p, unsigned int indent,
 						 const struct drm_gem_object *obj)
 {
-	drm_gem_cma_print_info(p, indent, obj);
+	const struct drm_gem_cma_object *cma_obj = to_drm_gem_cma_obj(obj);
+
+	drm_gem_cma_print_info(cma_obj, p, indent);
 }
 
 /**
···
  */
 static inline struct sg_table *drm_gem_cma_object_get_sg_table(struct drm_gem_object *obj)
 {
-	return drm_gem_cma_get_sg_table(obj);
+	struct drm_gem_cma_object *cma_obj = to_drm_gem_cma_obj(obj);
+
+	return drm_gem_cma_get_sg_table(cma_obj);
 }
 
 /*
···
  */
 static inline int drm_gem_cma_object_vmap(struct drm_gem_object *obj, struct dma_buf_map *map)
 {
-	return drm_gem_cma_vmap(obj, map);
+	struct drm_gem_cma_object *cma_obj = to_drm_gem_cma_obj(obj);
+
+	return drm_gem_cma_vmap(cma_obj, map);
 }
 
 /**
···
  */
 static inline int drm_gem_cma_object_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
 {
-	return drm_gem_cma_mmap(obj, vma);
+	struct drm_gem_cma_object *cma_obj = to_drm_gem_cma_obj(obj);
+
+	return drm_gem_cma_mmap(cma_obj, vma);
 }
 
 /*