looks good to me.

But maybe build_bug_on works too and more reasonable to detect such wrong usage.

From: Chen, Guchun <Guchun.Chen@amd.com>
Sent: Friday, September 10, 2021 12:30:14 PM
To: amd-gfx@lists.freedesktop.org <amd-gfx@lists.freedesktop.org>; dri-devel@lists.freedesktop.org <dri-devel@lists.freedesktop.org>; Koenig, Christian <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; Deucher, Alexander <Alexander.Deucher@amd.com>
Cc: Chen, Guchun <Guchun.Chen@amd.com>; Shi, Leslie <Yuliang.Shi@amd.com>
Subject: [PATCH] drm/ttm: add a BUG_ON in ttm_set_driver_manager when array bounds

Vendor will define their own memory types on top of TTM_PL_PRIV,
but call ttm_set_driver_manager directly without checking mem_type
value when setting up memory manager. So add such check to aware
the case when array bounds.

Signed-off-by: Leslie Shi <Yuliang.Shi@amd.com>
Signed-off-by: Guchun Chen <guchun.chen@amd.com>
---
include/drm/ttm/ttm_device.h | 1 +
1 file changed, 1 insertion(+)

diff --git a/include/drm/ttm/ttm_device.h b/include/drm/ttm/ttm_device.h
index 7a0f561c57ee..24ad76ca8022 100644
--- a/include/drm/ttm/ttm_device.h
+++ b/include/drm/ttm/ttm_device.h
@@ -308,6 +308,7 @@ ttm_manager_type(struct ttm_device *bdev, int mem_type)
static inline void ttm_set_driver_manager(struct ttm_device *bdev, int type,
                                           struct ttm_resource_manager *manager)
{
+       BUG_ON(type >= TTM_NUM_MEM_TYPES);
         bdev->man_drv[type] = manager;
}

--
2.17.1