The documentation of this new API has been overlooked during its
introduction. Fill the gap.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
 kernel/kthread.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/kernel/kthread.c b/kernel/kthread.c
index f3397cf7542a..b989aeaa441a 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -857,6 +857,18 @@ int kthreadd(void *unused)
 	return 0;
 }
 
+/**
+ * kthread_affine_preferred - Define a kthread's preferred affinity
+ * @p: thread created by kthread_create().
+ * @cpumask: preferred mask of CPUs (might not be online, must be possible) for @k
+ *           to run on.
+ *
+ * Similar to kthread_bind_mask() except that the affinity is not a requirement
+ * but rather a preference that can be constrained by CPU isolation or CPU hotplug.
+ * Must be called before the first wakeup of the kthread.
+ *
+ * Returns 0 if the affinity has been applied.
+ */
 int kthread_affine_preferred(struct task_struct *p, const struct cpumask *mask)
 {
 	struct kthread *kthread = to_kthread(p);
-- 
2.51.0