Hi Kees,
Thanks for your patch.
The switch statement is needed for multiple planes which is already approved in
this patch series.
https://patchwork.kernel.org/project/dri-devel/patch/20210728003126.1425028-13-anitha.chrisant...@intel.com/
This patch has dependencies on the previous patches in this series, and we are
waiting for reviews on those before this can be checked in.
Thanks,
Anitha
> -----Original Message-----
> From: Kees Cook <keesc...@chromium.org>
> Sent: Wednesday, August 25, 2021 11:18 AM
> To: Chrisanthus, Anitha <anitha.chrisant...@intel.com>
> Cc: Kees Cook <keesc...@chromium.org>; Dea, Edmund J
> <edmund.j....@intel.com>; David Airlie <airl...@linux.ie>; Daniel Vetter
> <dan...@ffwll.ch>; dri-devel@lists.freedesktop.org; Sam Ravnborg
> <s...@ravnborg.org>; linux-ker...@vger.kernel.org; linux-
> harden...@vger.kernel.org
> Subject: [PATCH] drm/kmb: Avoid warnings on impossible plane_id
>
> KMB_MAX_PLANES is defined as 1, yet kmb_plane_atomic_disable() had code
> for writing beyond 1. It is gated by a WARN_ON() that would skip it,
> though, but under some compiler versions, poor Dead Code Elimination
> wasn't optimizing away the unused switch cases, leading to array bounds
> warnings when building with -Warray-bounds:
>
> drivers/gpu/drm/kmb/kmb_plane.c:135:20: warning: array subscript 3 is
> above array bounds of 'struct layer_status[1]' [-Warray-bounds]
> drivers/gpu/drm/kmb/kmb_plane.c:132:20: warning: array subscript 2 is
> above array bounds of 'struct layer_status[1]' [-Warray-bounds]
> drivers/gpu/drm/kmb/kmb_plane.c:129:20: warning: array subscript 1 is
> above array bounds of 'struct layer_status[1]' [-Warray-bounds]
>
> Instead, just remove the switch statement entirely and adjust the index
> type to match the struct "id" member.
>
> Cc: Anitha Chrisanthus <anitha.chrisant...@intel.com>
> Cc: Edmund Dea <edmund.j....@intel.com>
> Cc: David Airlie <airl...@linux.ie>
> Cc: Daniel Vetter <dan...@ffwll.ch>
> Cc: dri-devel@lists.freedesktop.org
> Fixes: 7f7b96a8a0a1 ("drm/kmb: Add support for KeemBay Display")
> Signed-off-by: Kees Cook <keesc...@chromium.org>
> ---
> drivers/gpu/drm/kmb/kmb_plane.c | 18 ++----------------
> 1 file changed, 2 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/kmb/kmb_plane.c
> b/drivers/gpu/drm/kmb/kmb_plane.c
> index ecee6782612d..3d46e756f2fe 100644
> --- a/drivers/gpu/drm/kmb/kmb_plane.c
> +++ b/drivers/gpu/drm/kmb/kmb_plane.c
> @@ -113,7 +113,7 @@ static void kmb_plane_atomic_disable(struct
> drm_plane *plane,
> struct drm_atomic_state *state)
> {
> struct kmb_plane *kmb_plane = to_kmb_plane(plane);
> - int plane_id = kmb_plane->id;
> + unsigned char plane_id = kmb_plane->id;
> struct kmb_drm_private *kmb;
>
> kmb = to_kmb(plane->dev);
> @@ -121,21 +121,7 @@ static void kmb_plane_atomic_disable(struct
> drm_plane *plane,
> 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;
> - break;
> - case LAYER_1:
> - kmb->plane_status[plane_id].ctrl = LCD_CTRL_VL2_ENABLE;
> - break;
> - case LAYER_2:
> - kmb->plane_status[plane_id].ctrl = LCD_CTRL_GL1_ENABLE;
> - break;
> - case LAYER_3:
> - kmb->plane_status[plane_id].ctrl = LCD_CTRL_GL2_ENABLE;
> - break;
> - }
> -
> + kmb->plane_status[plane_id].ctrl = LCD_CTRL_VL1_ENABLE;
> kmb->plane_status[plane_id].disable = true;
> }
>
> --
> 2.30.2
