From 8aa2ab8d9777781f2ccc843ed660f07bfa494f05 Mon Sep 17 00:00:00 2001
From: Ivan K <krylov.r00t@gmail.com>
Date: Wed, 28 Feb 2024 16:33:40 +0300
Subject: [PATCH] Document the usbd_ep_write(dev, ep, 0, 0) trick

---
 inc/usbd_core.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/inc/usbd_core.h b/inc/usbd_core.h
index 587509f..bc30b86 100644
--- a/inc/usbd_core.h
+++ b/inc/usbd_core.h
@@ -269,6 +269,11 @@ typedef int32_t (*usbd_hw_ep_read)(uint8_t ep, void *buf, uint16_t blen);
  * \param buf pointer to data buffer
  * \param blen size of data will be written
  * \return number of written bytes
+ *
+ * The \ref usbd_evt_eptx event will fire for the endpoint once the
+ * write is \e complete. A trick commonly used is to enqueue a zero-length
+ * write as soon as the endpoint is configured, so that it would
+ * "complete", firing an event, the next time an IN request arrives.
  */
 typedef int32_t (*usbd_hw_ep_write)(uint8_t ep, const void *buf, uint16_t blen);