drm: refuse ADDFB2 ioctl for broken bigendian drivers

Drivers must set the quirk_addfb_prefer_host_byte_order quirk to make
the drm_mode_addfb() compat code work correctly on bigendian machines.

If they don't they interpret pixel_format values incorrectly for bug
compatibility, which in turn implies the ADDFB2 ioctl does not work
correctly then.  So block it to make userspace fallback to ADDFB.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20180907073213.20410-1-kraxel@redhat.com

drivers/gpu/drm/drm_crtc_internal.h

@@ -182,6 +182,8 @@ void drm_fb_release(struct drm_file *file_priv);
 
 int drm_mode_addfb(struct drm_device *dev, struct drm_mode_fb_cmd *or,
 		   struct drm_file *file_priv);
+int drm_mode_addfb2(struct drm_device *dev,
+		    void *data, struct drm_file *file_priv);
 int drm_mode_rmfb(struct drm_device *dev, u32 fb_id,
 		  struct drm_file *file_priv);
 
@@ -189,7 +191,7 @@ int drm_mode_rmfb(struct drm_device *dev, u32 fb_id,
 /* IOCTL */
 int drm_mode_addfb_ioctl(struct drm_device *dev,
 			 void *data, struct drm_file *file_priv);
-int drm_mode_addfb2(struct drm_device *dev,
+int drm_mode_addfb2_ioctl(struct drm_device *dev,
 			  void *data, struct drm_file *file_priv);
 int drm_mode_rmfb_ioctl(struct drm_device *dev,
 			void *data, struct drm_file *file_priv);

drivers/gpu/drm/drm_framebuffer.c

@@ -369,6 +369,30 @@ int drm_mode_addfb2(struct drm_device *dev,
 	return 0;
 }
 
+int drm_mode_addfb2_ioctl(struct drm_device *dev,
+			  void *data, struct drm_file *file_priv)
+{
+#ifdef __BIG_ENDIAN
+	if (!dev->mode_config.quirk_addfb_prefer_host_byte_order) {
+		/*
+		 * Drivers must set the
+		 * quirk_addfb_prefer_host_byte_order quirk to make
+		 * the drm_mode_addfb() compat code work correctly on
+		 * bigendian machines.
+		 *
+		 * If they don't they interpret pixel_format values
+		 * incorrectly for bug compatibility, which in turn
+		 * implies the ADDFB2 ioctl does not work correctly
+		 * then.  So block it to make userspace fallback to
+		 * ADDFB.
+		 */
+		DRM_DEBUG_KMS("addfb2 broken on bigendian");
+		return -EINVAL;
+	}
+#endif
+	return drm_mode_addfb2(dev, data, file_priv);
+}
+
 struct drm_mode_rmfb_work {
 	struct work_struct work;
 	struct list_head fbs;

drivers/gpu/drm/drm_ioctl.c

@@ -645,7 +645,7 @@ static const struct drm_ioctl_desc drm_ioctls[] = {
 	DRM_IOCTL_DEF(DRM_IOCTL_MODE_GETPROPBLOB, drm_mode_getblob_ioctl, DRM_UNLOCKED),
 	DRM_IOCTL_DEF(DRM_IOCTL_MODE_GETFB, drm_mode_getfb, DRM_UNLOCKED),
 	DRM_IOCTL_DEF(DRM_IOCTL_MODE_ADDFB, drm_mode_addfb_ioctl, DRM_UNLOCKED),
-	DRM_IOCTL_DEF(DRM_IOCTL_MODE_ADDFB2, drm_mode_addfb2, DRM_UNLOCKED),
+	DRM_IOCTL_DEF(DRM_IOCTL_MODE_ADDFB2, drm_mode_addfb2_ioctl, DRM_UNLOCKED),
 	DRM_IOCTL_DEF(DRM_IOCTL_MODE_RMFB, drm_mode_rmfb_ioctl, DRM_UNLOCKED),
 	DRM_IOCTL_DEF(DRM_IOCTL_MODE_PAGE_FLIP, drm_mode_page_flip_ioctl, DRM_MASTER|DRM_UNLOCKED),
 	DRM_IOCTL_DEF(DRM_IOCTL_MODE_DIRTYFB, drm_mode_dirtyfb_ioctl, DRM_MASTER|DRM_UNLOCKED),