diff --git a/configstore/1.0/ISurfaceFlingerConfigs.hal b/configstore/1.0/ISurfaceFlingerConfigs.hal
index 4403a90..318590d 100644
--- a/configstore/1.0/ISurfaceFlingerConfigs.hal
+++ b/configstore/1.0/ISurfaceFlingerConfigs.hal
@@ -16,6 +16,29 @@
 package android.hardware.configstore@1.0;
 
 interface ISurfaceFlingerConfigs {
+    /*
+     * The following two methods define (respectively):
+     *
+     * - The phase offset between hardware vsync and when apps are woken up by the
+     *   Choreographer callback
+     * - The phase offset between hardware vsync and when SurfaceFlinger wakes up
+     *   to consume input
+     *
+     * Their values may be tuned to trade off between display pipeline latency (both
+     * overall latency and the lengths of the app --> SF and SF --> display phases)
+     * and frame delivery jitter (which typically manifests as "jank" or "jerkiness"
+     * while interacting with the device). The default values must produce a
+     * relatively low amount of jitter at the expense of roughly two frames of
+     * app --> display latency, and unless significant testing is performed to avoid
+     * increased display jitter (both manual investigation using systrace [1] and
+     * automated testing using dumpsys gfxinfo [2] are recommended), they should not
+     * be modified.
+     *
+     * [1] https://developer.android.com/studio/profile/systrace.html
+     * [2] https://developer.android.com/training/testing/performance.html
+     */
     vsyncEventPhaseOffsetNs() generates (OptionalInt64 value);
+    vsyncSfEventPhaseOffsetNs() generates (OptionalInt64 value);
+
     useTripleFramebuffer() generates (OptionalBool value);
 };