When building with -Wincompatible-function-pointer-types-strict, a
warning designed to catch kernel control flow integrity (kCFI) issues at
build time, there is an instance in the new tiny DRM pixpaper driver:
drivers/gpu/drm/tiny/pixpaper.c:982:16: error: incompatible function pointer
types initializing 'enum drm_mode_status (*)(struct drm_crtc *, const struct
drm_display_mode *)' with an expression of type 'int (struct drm_crtc *, const
struct drm_display_mode *)'
[-Werror,-Wincompatible-function-pointer-types-strict]
982 | .mode_valid = pixpaper_mode_valid,
| ^~~~~~~~~~~~~~~~~~~
While 'int' and 'enum drm_mode_status' are ABI compatible, hence no
regular warning from -Wincompatible-function-pointer-types, the mismatch
will trigger a kCFI violation when pixpaper_mode_valid() is called
indirectly.
Update the return type of pixpaper_mode_valid() to be
'enum drm_mode_status' to clear up the warning and kCFI violation.
Fixes: c9e70639f591 ("drm: tiny: Add support for Mayqueen Pixpaper e-ink panel")
Signed-off-by: Nathan Chancellor <nat...@kernel.org>
---
drivers/gpu/drm/tiny/pixpaper.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/tiny/pixpaper.c b/drivers/gpu/drm/tiny/pixpaper.c
index b1379cb5f030..32598fb2fee7 100644
--- a/drivers/gpu/drm/tiny/pixpaper.c
+++ b/drivers/gpu/drm/tiny/pixpaper.c
@@ -968,8 +968,8 @@ static const struct drm_crtc_funcs pixpaper_crtc_funcs = {
.atomic_destroy_state = drm_atomic_helper_crtc_destroy_state,
};
-static int pixpaper_mode_valid(struct drm_crtc *crtc,
- const struct drm_display_mode *mode)
+static enum drm_mode_status
+pixpaper_mode_valid(struct drm_crtc *crtc, const struct drm_display_mode *mode)
{
if (mode->hdisplay == PIXPAPER_WIDTH &&
mode->vdisplay == PIXPAPER_HEIGHT) {
---
base-commit: 490b30fbaca2abbd6afa8bdc7e2df329b5d82412
change-id: 20250908-drm-pixpaper-fix-mode_valid-return-type-4228e531193b
Best regards,
--
Nathan Chancellor <nat...@kernel.org>
