i915: Add GEM ioctl to get available aperture size.

This will let userland know when to submit its batchbuffers, before they get
too big to fit in the aperture.

Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 901e80c..cc8a9f3 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -502,6 +502,8 @@
 			struct drm_file *file_priv);
 int i915_gem_get_tiling(struct drm_device *dev, void *data,
 			struct drm_file *file_priv);
+int i915_gem_get_aperture_ioctl(struct drm_device *dev, void *data,
+				struct drm_file *file_priv);
 void i915_gem_load(struct drm_device *dev);
 int i915_gem_proc_init(struct drm_minor *minor);
 void i915_gem_proc_cleanup(struct drm_minor *minor);