drm/i915: compile-time consistency check on __EXEC_OBJECT flags

Two different sets of flag bits are stored in the 'flags' member of a
'struct drm_i915_gem_exec_object2', and they're defined in two different
source files, increasing the risk of an accidental clash.

Some flags in this field are supplied by the user; these are defined in
i915_drm.h, and they start from the LSB and work up.

Other flags are defined in i915_gem_execbuffer, for internal use within
that file only; they start from the MSB and work down.

So here we add a compile-time check that the two sets of flags do not
overlap, which would cause all sorts of confusion.

Signed-off-by: Dave Gordon <david.s.gordon@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1468504324-12690-1-git-send-email-david.s.gordon@intel.com

1 files changed, 6 insertions, 5 deletions

diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index d7e81a3886fd..51b9360bb376 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -698,12 +698,13 @@ struct drm_i915_gem_exec_object2 {
          */
         __u64 offset;
 
-#define EXEC_OBJECT_NEEDS_FENCE (1<<0)
-#define EXEC_OBJECT_NEEDS_GTT   (1<<1)
-#define EXEC_OBJECT_WRITE       (1<<2)
+#define EXEC_OBJECT_NEEDS_FENCE          (1<<0)
+#define EXEC_OBJECT_NEEDS_GTT            (1<<1)
+#define EXEC_OBJECT_WRITE                (1<<2)
 #define EXEC_OBJECT_SUPPORTS_48B_ADDRESS (1<<3)
-#define EXEC_OBJECT_PINNED      (1<<4)
-#define __EXEC_OBJECT_UNKNOWN_FLAGS -(EXEC_OBJECT_PINNED<<1)
+#define EXEC_OBJECT_PINNED               (1<<4)
+/* All remaining bits are MBZ and RESERVED FOR FUTURE USE */
+#define __EXEC_OBJECT_UNKNOWN_FLAGS     (-(EXEC_OBJECT_PINNED<<1))
         __u64 flags;
 
         __u64 rsvd1;