drm/i915: Replace __I915__ with typesafe variant

Ville pointed out the GCCism __builtin_types_compatible_p() that we
could use to replace our heavily casted presumption __I915__ macro that
was based on comparing struct sizes.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 04dd611..db56b26 100644 (file)
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1595,9 +1595,6 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
        if (!drm_core_check_feature(dev, DRIVER_MODESET) && !dev->agp)
                return -EINVAL;
 
-       /* For the ugly agnostic INTEL_INFO macro */
-       BUILD_BUG_ON(sizeof(*dev_priv) == sizeof(*dev));
-
        dev_priv = kzalloc(sizeof(*dev_priv), GFP_KERNEL);
        if (dev_priv == NULL)
                return -ENOMEM;

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index eb99a10..2af0071 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2004,8 +2004,16 @@ struct drm_i915_cmd_table {
 };
 
 /* Note that the (struct drm_i915_private *) cast is just to shut up gcc. */
-#define __I915__(p)    ((sizeof(*(p)) == sizeof(struct drm_i915_private)) ? \
-                        (struct drm_i915_private *)(p) : to_i915(p))
+#define __I915__(p) ({ \
+       struct drm_i915_private *__p; \
+       if (__builtin_types_compatible_p(typeof(*p), struct drm_i915_private)) \
+               __p = (struct drm_i915_private *)p; \
+       else if (__builtin_types_compatible_p(typeof(*p), struct drm_device)) \
+               __p = to_i915((struct drm_device *)p); \
+       else \
+               BUILD_BUG(); \
+       __p; \
+})
 #define INTEL_INFO(p)  (&__I915__(p)->info)
 #define INTEL_DEVID(p) (INTEL_INFO(p)->device_id)