1 files changed, 5 insertions, 5 deletions

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 6abf103fb7f8..bf85733597ec 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -565,8 +565,8 @@ struct pmu {
 
         int                             *pmu_disable_count;
 
-        void (*pmu_enable)              (struct pmu *pmu);
-        void (*pmu_disable)             (struct pmu *pmu);
+        void (*pmu_enable)              (struct pmu *pmu); /* optional */
+        void (*pmu_disable)             (struct pmu *pmu); /* optional */
 
         /*
          * Should return -ENOENT when the @event doesn't match this PMU.
@@ -590,19 +590,19 @@ struct pmu {
          * Start the transaction, after this ->enable() doesn't need to
          * do schedulability tests.
          */
-        void (*start_txn)       (struct pmu *pmu);
+        void (*start_txn)       (struct pmu *pmu); /* optional */
         /*
          * If ->start_txn() disabled the ->enable() schedulability test
          * then ->commit_txn() is required to perform one. On success
          * the transaction is closed. On error the transaction is kept
          * open until ->cancel_txn() is called.
          */
-        int  (*commit_txn)      (struct pmu *pmu);
+        int  (*commit_txn)      (struct pmu *pmu); /* optional */
         /*
          * Will cancel the transaction, assumes ->disable() is called
          * for each successfull ->enable() during the transaction.
          */
-        void (*cancel_txn)      (struct pmu *pmu);
+        void (*cancel_txn)      (struct pmu *pmu); /* optional */
 };
 
 /**