drm/i915: Check the framebuffer offset

The current code can't deal with framebuffers with an offset. Return an
error when trying to create such a framebuffer until the rest of the
code is fixed to handle them.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -8393,6 +8393,10 @@ int intel_framebuffer_init(struct drm_device *dev,
 		return -EINVAL;
 	}
 
+	/* FIXME need to adjust LINOFF/TILEOFF accordingly. */
+	if (mode_cmd->offsets[0] != 0)
+		return -EINVAL;
+
 	ret = drm_framebuffer_init(dev, &intel_fb->base, &intel_fb_funcs);
 	if (ret) {
 		DRM_ERROR("framebuffer init failed %d\n", ret);