diff --git a/camera/device/3.2/ICameraDeviceSession.hal b/camera/device/3.2/ICameraDeviceSession.hal
index e92d756..a4816b4 100644
--- a/camera/device/3.2/ICameraDeviceSession.hal
+++ b/camera/device/3.2/ICameraDeviceSession.hal
@@ -152,6 +152,7 @@
      *             camera3_stream_configuration_t->operation_mode requirements
      *             for non-NORMAL mode, or the requested operation_mode is not
      *             supported by the HAL.
+     *           - Unsupported usage flag
      *         The camera service cannot filter out all possible illegal stream
      *         configurations, since some devices may support more simultaneous
      *         streams or larger stream resolutions than the minimum required
diff --git a/camera/device/3.2/types.hal b/camera/device/3.2/types.hal
index c7d38c1..ba5bbe0 100644
--- a/camera/device/3.2/types.hal
+++ b/camera/device/3.2/types.hal
@@ -248,6 +248,12 @@
      * streamType INPUT, the value of this field is always 0. For all streams
      * passed via configureStreams(), the HAL must set its own
      * additional usage flags in its output HalStreamConfiguration.
+     *
+     * The usage flag for an output stream may be bitwise combination of usage
+     * flags for multiple consumers, for the purpose of sharing one camera
+     * stream between those consumers. The HAL must fail configureStreams call
+     * with ILLEGAL_ARGUMENT if the combined flags cannot be supported due to
+     * imcompatible buffer format, dataSpace, or other hardware limitations.
      */
     ConsumerUsageFlags usage;