doc: explicitly state that the ctxless event poll callback can be NULL

This is mentioned later in the text, but state it in the argument's
description too.

Signed-off-by: Bartosz Golaszewski <bartekgola@gmail.com>

diff --git a/include/gpiod.h b/include/gpiod.h
index b00b9a9f99acc6ced744870817c4e89a6c7a993f..b14fadc7f4f37a053ae66e33272095f04134b8aa 100644 (file)
--- a/include/gpiod.h
+++ b/include/gpiod.h
@@ -260,7 +260,8 @@ int gpiod_ctxless_event_loop(const char *device, unsigned int offset,
  * @param active_low The active state of this line - true if low.
  * @param consumer Name of the consumer.
  * @param timeout Maximum wait time for each iteration.
- * @param poll_cb Callback function to call when waiting for events.
+ * @param poll_cb Callback function to call when waiting for events. Can
+ *                be NULL.
  * @param event_cb Callback function to call on event occurrence.
  * @param data User data passed to the callback.
  * @return 0 no errors were encountered, -1 if an error occurred.