drm: Make sure the DRM offset matches the CPU

The pgoff option in mmap() is defined as an unsigned long
so the offset generated by DRM needs to fit into
BITS_PER_LONG for the CPU in question.

Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_gem.c

@@ -68,8 +68,18 @@
  * We make up offsets for buffer objects so we can recognize them at
  * mmap time.
  */
+
+/* pgoff in mmap is an unsigned long, so we need to make sure that
+ * the faked up offset will fit
+ */
+
+#if BITS_PER_LONG == 64
 #define DRM_FILE_PAGE_OFFSET_START ((0xFFFFFFFFUL >> PAGE_SHIFT) + 1)
 #define DRM_FILE_PAGE_OFFSET_SIZE ((0xFFFFFFFFUL >> PAGE_SHIFT) * 16)
+#else
+#define DRM_FILE_PAGE_OFFSET_START ((0xFFFFFFFUL >> PAGE_SHIFT) + 1)
+#define DRM_FILE_PAGE_OFFSET_SIZE ((0xFFFFFFFUL >> PAGE_SHIFT) * 16)
+#endif
 
 /**
  * Initialize the GEM device fields