From: =?UTF-8?q?Noralf=20Tr=C3=B8nnes?= <noralf@tronnes.org>
Date: Tue, 7 Nov 2017 20:13:42 +0100
Subject: drm/cma-helper: Turn to_drm_gem_cma_obj() into a macro
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Git-commit: 8d25ccebef55b8fc47b674f24ccdccbef08e2f32
Patch-mainline: v4.16-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

This allows the argument to be a const.

The other option was to keep it an inline function and make the argument
a const:

static inline struct drm_gem_cma_object *
to_drm_gem_cma_obj(const struct drm_gem_object *gem_obj)
{
	return container_of(gem_obj, struct drm_gem_cma_object, base);
}

This will happily return a non-const pointer to the drm_gem_cma_object
based on a const pointer to the contained drm_gem_object, thus creating
const-safety problems.

There was an attempt to fix the problem in the container_of() macro
itself (see https://lkml.org/lkml/2017/5/19/381) but the patch seems to
have fallen through the cracks. It would require turning this inline
function into a macro.

By making this a macro now, we will benefit from a possible future
enhancement of container_of(). We don't loose type checking by doing
this, container_of() takes care of that.

Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171107191348.17555-7-noralf@tronnes.org

Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 include/drm/drm_gem_cma_helper.h |    7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

--- a/include/drm/drm_gem_cma_helper.h
+++ b/include/drm/drm_gem_cma_helper.h
@@ -20,11 +20,8 @@ struct drm_gem_cma_object {
 	void *vaddr;
 };
 
-static inline struct drm_gem_cma_object *
-to_drm_gem_cma_obj(struct drm_gem_object *gem_obj)
-{
-	return container_of(gem_obj, struct drm_gem_cma_object, base);
-}
+#define to_drm_gem_cma_obj(gem_obj) \
+	container_of(gem_obj, struct drm_gem_cma_object, base)
 
 #ifndef CONFIG_MMU
 #define DRM_GEM_CMA_UNMAPPED_AREA_FOPS \