[PATCH v2] drm: refuse ADDFB2 ioctl for broken bigendian drivers

[Gerd Hoffmann <kraxel@redhat.com>]

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>
---
 drivers/gpu/drm/drm_crtc_internal.h |  6 ++++--
 drivers/gpu/drm/drm_framebuffer.c   | 24 ++++++++++++++++++++++++
 drivers/gpu/drm/drm_ioctl.c         |  2 +-
 3 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_crtc_internal.h b/drivers/gpu/drm/drm_crtc_internal.h
index b613227633..6719e1c8df 100644
--- a/drivers/gpu/drm/drm_crtc_internal.h
+++ b/drivers/gpu/drm/drm_crtc_internal.h
@@ -174,6 +174,8 @@ 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);
 
@@ -181,8 +183,8 @@ 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,
-		    void *data, struct drm_file *file_priv);
+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);
 int drm_mode_getfb(struct drm_device *dev,
diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c
index f863f8a20f..fb7528444c 100644
--- a/drivers/gpu/drm/drm_framebuffer.c
+++ b/drivers/gpu/drm/drm_framebuffer.c
@@ -363,6 +363,30 @@ 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;
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index ea10e9a26a..6b4a633b42 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/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),
-- 
2.9.3