[PATCH] Improve skeleton example

Fill out stub functions and comments. Mark required vs not required
io_engine hooks.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/engines/fio-engine-skeleton_external.c b/engines/fio-engine-skeleton_external.c
index 497baa6c89f5791618bcdea97ee34b4ba6c01582..2c330f0c3f69e05ea4663dcd1157bbd3f233c68c 100644 (file)
--- a/engines/fio-engine-skeleton_external.c
+++ b/engines/fio-engine-skeleton_external.c
@@ -21,6 +21,77 @@
  * for external modules, they should be gotten through dlsym()
  */
 
+/*
+ * The ->event() hook is called to match an event number with an io_u.
+ * After the core has called ->getevents() and it has returned eg 3,
+ * the ->event() hook must return the 3 events that have completed for
+ * subsequent calls to ->event() with [0-2]. Required.
+ */
+static struct io_u *fio_skeleton_event(struct thread_data *td, int event)
+{
+       return NULL;
+}
+
+/*
+ * The ->getevents() hook is used to reap completion events from an async
+ * io engine. It returns the number of completed events since the last call,
+ * which may then be retrieved by calling the ->event() hook with the event
+ * numbers. Required.
+ */
+static int fio_skeleton_getevents(struct thread_data *td, int min, int max,
+                                 struct timespec *t)
+{
+       return 0;
+}
+
+/*
+ * The ->cancel() hook attempts to cancel the io_u. Only relevant for
+ * async io engines, and need not be supported.
+ */
+static int fio_skeleton_cancel(struct thread_data *td, struct io_u *io_u)
+{
+       return 0;
+}
+
+/*
+ * The ->queue() hook is responsible for initiating io on the io_u
+ * being passed in. If the io engine is a synchronous one, io may complete
+ * before ->queue() returns. Required.
+ */
+static int fio_skeleton_queue(struct thread_data *td, struct io_u *io_u)
+{
+       return 0;
+}
+
+/*
+ * The ->prep() function is called for each io_u prior to being submitted
+ * with ->queue(). This hook allows the io engine to perform any
+ * preperatory actions on the io_u, before being submitted. Not required.
+ */
+static int fio_skeleton_prep(struct thread_data *td, struct io_u *io_u)
+{
+       return 0;
+}
+
+/*
+ * The init function is called once per thread/process, and should set up
+ * any structures that this io engine requires to keep track of io. Not
+ * required.
+ */
+static int fio_skeleton_init(struct thread_data *td)
+{
+       return 0;
+}
+
+/*
+ * This is paired with the ->init() funtion and is called when a thread is
+ * done doing io. Should tear down anything setup by the ->init() function.
+ * Not required.
+ */
+static void fio_skeleton_cleanup(struct thread_data *td)
+{
+}
+
 /*
  * Note that the structure is exported, so that fio can get it via
  * dlsym(..., "ioengine");
@@ -31,6 +102,7 @@ struct ioengine_ops ioengine = {
        .init           = fio_skeleton_init,
        .prep           = fio_skeleton_prep,
        .queue          = fio_skeleton_queue,
+       .cancel         = fio_skeleton_cancel,
        .getevents      = fio_skeleton_getevents,
        .event          = fio_skeleton_event,
        .cleanup        = fio_skeleton_cleanup,