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drm/kmb: fix array bounds warning

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gcc warns about an out-of-bounds access when the using nonzero
values for 'plane_id' on kmb->plane_status:

drivers/gpu/drm/kmb/kmb_plane.c: In function 'kmb_plane_atomic_disable':
drivers/gpu/drm/kmb/kmb_plane.c:128:20: warning: array subscript 3 is above array bounds of 'struct layer_status[1]' [-Warray-bounds]
  128 |   kmb->plane_status[plane_id].ctrl = LCD_CTRL_GL2_ENABLE;
      |   ~~~~~~~~~~~~~~~~~^~~~~~~~~~
drivers/gpu/drm/kmb/kmb_plane.c:125:20: warning: array subscript 2 is above array bounds of 'struct layer_status[1]' [-Warray-bounds]
  125 |   kmb->plane_status[plane_id].ctrl = LCD_CTRL_GL1_ENABLE;
      |   ~~~~~~~~~~~~~~~~~^~~~~~~~~~
drivers/gpu/drm/kmb/kmb_plane.c:122:20: warning: array subscript 1 is above array bounds of 'struct layer_status[1]' [-Warray-bounds]
  122 |   kmb->plane_status[plane_id].ctrl = LCD_CTRL_VL2_ENABLE;

Having the array truncated to one entry seems intentional, so add
a range check before indexing it to make it clearer what is going
on and shut up the warning.

I received the warning from the kernel test robot after a private
patch that turns on Warray-bounds unconditionally.

Fixes: 7f7b96a8a0 ("drm/kmb: Add support for KeemBay Display")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Anitha Chrisanthus <anitha.chrisanthus@intel.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20201129200927.1854104-1-arnd@kernel.org
This commit is contained in:
Arnd Bergmann 2020-11-29 21:09:08 +01:00 committed by Sam Ravnborg
parent 9dbf1a4516
commit 98fdd0042c
1 changed files with 3 additions and 0 deletions
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3
drivers/gpu/drm/kmb/kmb_plane.c
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@ -114,6 +114,9 @@ static void kmb_plane_atomic_disable(struct drm_plane *plane,
kmb = to_kmb(plane->dev);
if (WARN_ON(plane_id >= KMB_MAX_PLANES))
return;
switch (plane_id) {
case LAYER_0:
kmb->plane_status[plane_id].ctrl = LCD_CTRL_VL1_ENABLE;