diff --git a/libweston/backend-drm/drm-internal.h b/libweston/backend-drm/drm-internal.h
index 69018cbcf..5280b4a39 100644
--- a/libweston/backend-drm/drm-internal.h
+++ b/libweston/backend-drm/drm-internal.h
@@ -868,17 +868,17 @@ drm_output_set_mode(struct weston_output *base,
 		    const char *modeline);
 
 void
-drm_property_info_populate(struct drm_device *device,
+drm_property_info_populate(const struct drm_device *device,
 		           const struct drm_property_info *src,
 			   struct drm_property_info *info,
 			   unsigned int num_infos,
-			   drmModeObjectProperties *props);
+			   const drmModeObjectProperties *props);
 uint64_t
-drm_property_get_value(struct drm_property_info *info,
+drm_property_get_value(const struct drm_property_info *info,
 		       const drmModeObjectProperties *props,
 		       uint64_t def);
-uint64_t *
-drm_property_get_range_values(struct drm_property_info *info,
+const uint64_t *
+drm_property_get_range_values(const struct drm_property_info *info,
 			      const drmModeObjectProperties *props);
 int
 drm_plane_populate_formats(struct drm_plane *plane, const drmModePlane *kplane,
diff --git a/libweston/backend-drm/drm.c b/libweston/backend-drm/drm.c
index dd75ad78b..b01301a61 100644
--- a/libweston/backend-drm/drm.c
+++ b/libweston/backend-drm/drm.c
@@ -1428,8 +1428,8 @@ drm_plane_create(struct drm_device *device, const drmModePlane *kplane)
 	struct weston_compositor *compositor = b->compositor;
 	struct drm_plane *plane, *tmp;
 	drmModeObjectProperties *props;
-	uint64_t *zpos_range_values;
-	uint64_t *alpha_range_values;
+	const uint64_t *zpos_range_values;
+	const uint64_t *alpha_range_values;
 
 	plane = zalloc(sizeof(*plane));
 	if (!plane) {
diff --git a/libweston/backend-drm/kms.c b/libweston/backend-drm/kms.c
index edc9ec674..71533e195 100644
--- a/libweston/backend-drm/kms.c
+++ b/libweston/backend-drm/kms.c
@@ -389,7 +389,7 @@ enum drm_state_apply_mode {
  * @param def Value to return if property is not found
  */
 uint64_t
-drm_property_get_value(struct drm_property_info *info,
+drm_property_get_value(const struct drm_property_info *info,
 		       const drmModeObjectProperties *props,
 		       uint64_t def)
 {
@@ -437,8 +437,8 @@ drm_property_get_value(struct drm_property_info *info,
  * @param info Internal structure for property to look up
  * @param props Raw KMS properties for the target object
  */
-uint64_t *
-drm_property_get_range_values(struct drm_property_info *info,
+const uint64_t *
+drm_property_get_range_values(const struct drm_property_info *info,
 			      const drmModeObjectProperties *props)
 {
 	unsigned int i;
@@ -571,11 +571,11 @@ wdrm_vrr_enabled_from_output(struct drm_output *drm_output)
  * @param props DRM object properties for the object
  */
 void
-drm_property_info_populate(struct drm_device *device,
+drm_property_info_populate(const struct drm_device *device,
 		           const struct drm_property_info *src,
 			   struct drm_property_info *info,
 			   unsigned int num_infos,
-			   drmModeObjectProperties *props)
+			   const drmModeObjectProperties *props)
 {
 	drmModePropertyRes *prop;
 	unsigned i, j;