drm/i915: Use offsetof() to calculate the offset of members in PVINFO page

To get the offset of the members in PVINFO page, offsetof() looks much
better than the tricky approach in current code.

v7:

- Move "offsetof()" modification into a dedicated patch. (Joonas)

Suggested-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Zhi Wang <zhi.a.wang@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1466078825-6662-3-git-send-email-zhi.a.wang@intel.com
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

diff --git a/drivers/gpu/drm/i915/i915_pvinfo.h b/drivers/gpu/drm/i915/i915_pvinfo.h
index e61144d45a94c6b0217892149de8bd3e2c67850c..c0cb2974caacdb0357b8fcde1a585da51ead7b43 100644 (file)
--- a/drivers/gpu/drm/i915/i915_pvinfo.h
+++ b/drivers/gpu/drm/i915/i915_pvinfo.h
@@ -104,7 +104,7 @@ struct vgt_if {
 } __packed;
 
 #define vgtif_reg(x) \
-       _MMIO((VGT_PVINFO_PAGE + (long)&((struct vgt_if *)NULL)->x))
+       _MMIO((VGT_PVINFO_PAGE + offsetof(struct vgt_if, x)))
 
 /* vGPU display status to be used by the host side */
 #define VGT_DRV_DISPLAY_NOT_READY 0