[RFCv2 04/13] drm: add DRM_MODE_PROP_DYNAMIC property flag

[Rob Clark <robdclark@gmail.com>]

This indicates to userspace that the property is something that can
be set dynamically without requiring a "test" step to check if the
hw is capable.  This allows a userspace compositor, such as weston,
to avoid an extra ioctl to check whether it needs to fall-back to
GPU to composite some surface prior to submission of GPU render
commands.
---
 include/uapi/drm/drm_mode.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
index 35921ba..15db837 100644
--- a/include/uapi/drm/drm_mode.h
+++ b/include/uapi/drm/drm_mode.h
@@ -232,6 +232,15 @@ struct drm_mode_get_connector {
 #define DRM_MODE_PROP_BLOB	(1<<4)
 #define DRM_MODE_PROP_BITMASK	(1<<5) /* bitmask of enumerated types */
 #define DRM_MODE_PROP_OBJECT	(1<<6) /* drm mode object */
+/* Properties that are not dynamic cannot safely be changed without a
+ * atomic-modeset / atomic-pageflip test step.  But if userspace is
+ * only changing dynamic properties, it is guaranteed that the change
+ * will not exceed hw limits, so no test step is required.
+ *
+ * Note that fb_id properties are a bit ambiguous.. they of course can
+ * be changed dynamically, assuming the pixel format does not change.
+ */
+#define DRM_MODE_PROP_DYNAMIC	(1<<24)
 
 struct drm_mode_property_enum {
 	__u64 value;
-- 
1.8.3.1