[PATCH] drm/vmwgfx: Don't memcmp equivalent pointers

[Zack Rusin]

On Thu, Mar 28, 2024 at 3:31 PM Ian Forbes <ian.forbes at broadcom.com> wrote:
>
> These pointers are frequently the same and memcmp does not compare the pointers
> before comparing their contents so this was wasting cycles comparing 16 KiB of
> memory which will always be equal.
>
> Fixes: bb6780aa5a1d9 ("drm/vmwgfx: Diff cursors when using cmds")
> Signed-off-by: Ian Forbes <ian.forbes at broadcom.com>
> ---
>  drivers/gpu/drm/vmwgfx/vmwgfx_kms.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
> index cd4925346ed4..fbcce84e2f4c 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
> @@ -216,7 +216,7 @@ static bool vmw_du_cursor_plane_has_changed(struct vmw_plane_state *old_vps,
>         new_image = vmw_du_cursor_plane_acquire_image(new_vps);
>
>         changed = false;
> -       if (old_image && new_image)
> +       if (old_image && new_image && (old_image != new_image))
>                 changed = memcmp(old_image, new_image, size) != 0;
>
>         return changed;
> --
> 2.34.1
>

The patch looks good but please use "dim checkpatch" and fix the
issues it found. For the "Fixes:" line you also want to use "dim
fixes".

z