diff --git a/os/hal/include/usb.h b/os/hal/include/usb.h
index 9cb933b2d..a99b9f511 100644
--- a/os/hal/include/usb.h
+++ b/os/hal/include/usb.h
@@ -399,8 +399,6 @@ typedef const USBDescriptor * (*usbgetdescriptor_t)(USBDriver *usbp,
  * @details The received size can be different from the size specified in
  *          @p usbStartReceiveI() because the last packet could have a size
  *          different from the expected one.
- * @pre     The OUT endpoint must have been configured in transaction mode
- *          in order to use this function.
  *
  * @param[in] usbp      pointer to the @p USBDriver object
  * @param[in] ep        endpoint number
@@ -411,20 +409,6 @@ typedef const USBDescriptor * (*usbgetdescriptor_t)(USBDriver *usbp,
 #define usbGetReceiveTransactionSizeI(usbp, ep)                             \
   usb_lld_get_transaction_size(usbp, ep)
 
-/**
- * @brief   Returns the exact size of a received packet.
- * @pre     The OUT endpoint must have been configured in packet mode
- *          in order to use this function.
- *
- * @param[in] usbp      pointer to the @p USBDriver object
- * @param[in] ep        endpoint number
- * @return              Received data size.
- *
- * @iclass
- */
-#define usbGetReceivePacketSizeI(usbp, ep)                                  \
-  usb_lld_get_packet_size(usbp, ep)
-
 /**
  * @brief   Request transfer setup.
  * @details This macro is used by the request handling callbacks in order to
diff --git a/os/hal/platforms/STM32/OTGv1/stm32_otg.h b/os/hal/platforms/STM32/OTGv1/stm32_otg.h
index 4c83a62eb..7e08fae7f 100644
--- a/os/hal/platforms/STM32/OTGv1/stm32_otg.h
+++ b/os/hal/platforms/STM32/OTGv1/stm32_otg.h
@@ -801,6 +801,14 @@ typedef struct {
 #define DIEPTSIZ_XFRSIZ(n)      ((n)<<0)    /**< Transfer size value.       */
 /** @} */
 
+/**
+ * @name DTXFSTS register bit definitions.
+ * @{
+ */
+#define DTXFSTS_INEPTFSAV_MASK  (0xFFFF<<0) /**< IN endpoint TxFIFO space
+                                                 available.                 */
+/** @} */
+
 /**
  * @name DOEPCTL register bit definitions.
  * @{
diff --git a/os/hal/src/usb.c b/os/hal/src/usb.c
index afe6f471c..2bf845e6e 100644
--- a/os/hal/src/usb.c
+++ b/os/hal/src/usb.c
@@ -354,8 +354,6 @@ void usbDisableEndpointsI(USBDriver *usbp) {
 
 /**
  * @brief   Prepares for a receive transaction on an OUT endpoint.
- * @pre     In order to use this function the endpoint must have been
- *          initialized in transaction mode.
  * @post    The endpoint is ready for @p usbStartReceiveI().
  * @note    This function can be called both in ISR and thread context.
  *
@@ -379,8 +377,6 @@ void usbPrepareReceive(USBDriver *usbp, usbep_t ep, uint8_t *buf, size_t n) {
 
 /**
  * @brief   Prepares for a transmit transaction on an IN endpoint.
- * @pre     In order to use this function the endpoint must have been
- *          initialized in transaction mode.
  * @post    The endpoint is ready for @p usbStartTransmitI().
  * @note    This function can be called both in ISR and thread context.
  * @note    The queue must contain at least the amount of data specified
@@ -407,8 +403,6 @@ void usbPrepareTransmit(USBDriver *usbp, usbep_t ep,
 
 /**
  * @brief   Prepares for a receive transaction on an OUT endpoint.
- * @pre     In order to use this function the endpoint must have been
- *          initialized in transaction mode.
  * @post    The endpoint is ready for @p usbStartReceiveI().
  * @note    This function can be called both in ISR and thread context.
  * @note    The queue must have enough free space to accommodate the
@@ -438,8 +432,6 @@ void usbPrepareQueuedReceive(USBDriver *usbp, usbep_t ep,
 
 /**
  * @brief   Prepares for a transmit transaction on an IN endpoint.
- * @pre     In order to use this function the endpoint must have been
- *          initialized in transaction mode.
  * @post    The endpoint is ready for @p usbStartTransmitI().
  * @note    This function can be called both in ISR and thread context.
  * @note    The transmit transaction size is equal to the data contained