Index: sys/cam/cam_sim.c
===================================================================
--- sys/cam/cam_sim.c
+++ sys/cam/cam_sim.c
@@ -127,6 +127,24 @@
 	return (sim);
 }
 
+/**
+ * @brief frees up the sim
+ *
+ * Frees up the CAM @c sim and optionally the devq. After this call returns, no
+ * further @c sim_action or @c sim_poll requests will make it to the driver. The
+ * driver is responsible for cleaning up all requests submitted via sim_action
+ * that were received prior to calling this function.
+ *
+ * This function asserts that the mtx associated with this sim, if any, is
+ * locked when this function is called. It will remain locked. Once this
+ * function returns, CAM will cease using that mutex, however.
+ *
+ * This function will wait for all outstanding reference to the sim to clear
+ * before returning.
+ *
+ * @param sim          The sim to free
+ * @param free_devq    Free the devq associated with the sim at creation.
+ */
 void
 cam_sim_free(struct cam_sim *sim, int free_devq)
 {