thunderbolt: Update ctl.c function documentation

Make ctl.c function documentation compliant with current kernel-doc
standards. No functional changes.

Signed-off-by: Alan Borzeszkowski <[e-mail]>
Signed-off-by: Mika Westerberg <[e-mail]>

drivers/thunderbolt/ctl.c

···
  *
  * This is refcounted object so when you are done with this, call
  * tb_cfg_request_put() to it.
+ *
+ * Return: &struct tb_cfg_request on success, %NULL otherwise.
  */
 struct tb_cfg_request *tb_cfg_request_alloc(void)
 {
···
  *
  * len must be a multiple of four.
  *
- * Return: Returns 0 on success or an error code on failure.
+ * Return: %0 on success, negative errno otherwise.
  */
 static int tb_ctl_tx(struct tb_ctl *ctl, const void *data, size_t len,
 		     enum tb_cfg_pkg_type type)
···
  *
  * This queues @req on the given control channel without waiting for it
  * to complete. When the request completes @callback is called.
+ *
+ * Return: %0 on success, negative errno otherwise.
  */
 int tb_cfg_request(struct tb_ctl *ctl, struct tb_cfg_request *req,
 		   void (*callback)(void *), void *callback_data)
···
  * triggers the request is canceled before function returns. Note the
  * caller needs to make sure only one message for given switch is active
  * at a time.
+ *
+ * Return: &struct tb_cfg_result with non-zero @err field if error
+ * has occurred.
  */
 struct tb_cfg_result tb_cfg_request_sync(struct tb_ctl *ctl,
 					 struct tb_cfg_request *req,
···
  *
  * cb will be invoked once for every hot plug event.
  *
- * Return: Returns a pointer on success or NULL on failure.
+ * Return: Pointer to &struct tb_ctl, %NULL on failure.
  */
 struct tb_ctl *tb_ctl_alloc(struct tb_nhi *nhi, int index, int timeout_msec,
 			    event_cb cb, void *cb_data)
···
  * @route: Router that originated the event
  * @error: Pointer to the notification package
  *
- * Call this as response for non-plug notification to ack it. Returns
- * %0 on success or an error code on failure.
+ * Call this as a response for non-plug notification to ack it.
+ *
+ * Return: %0 on success, negative errno otherwise.
  */
 int tb_cfg_ack_notification(struct tb_ctl *ctl, u64 route,
 			    const struct cfg_error_pkg *error)
···
  * @port: Port where the hot plug/unplug happened
  * @unplug: Ack hot plug or unplug
  *
- * Call this as response for hot plug/unplug event to ack it.
- * Returns %0 on success or an error code on failure.
+ * Call this as a response for hot plug/unplug event to ack it.
+ *
+ * Return: %0 on success, negative errno otherwise.
  */
 int tb_cfg_ack_plug(struct tb_ctl *ctl, u64 route, u32 port, bool unplug)
 {
···
  * If the switch at route is incorrectly configured then we will not receive a
  * reply (even though the switch will reset). The caller should check for
  * -ETIMEDOUT and attempt to reconfigure the switch.
+ *
+ * Return: &struct tb_cfg_result with non-zero @err field if error
+ * has occurred.
  */
 struct tb_cfg_result tb_cfg_reset(struct tb_ctl *ctl, u64 route)
 {
···
  * @timeout_msec: Timeout in ms how long to wait for the response
  *
  * Reads from router config space without translating the possible error.
+ *
+ * Return: &struct tb_cfg_result with non-zero @err field if error
+ * has occurred.
  */
 struct tb_cfg_result tb_cfg_read_raw(struct tb_ctl *ctl, void *buffer,
 		u64 route, u32 port, enum tb_cfg_space space,
···
  * @timeout_msec: Timeout in ms how long to wait for the response
  *
  * Writes to router config space without translating the possible error.
+ *
+ * Return: &struct tb_cfg_result with non-zero @err field if error
+ * has occurred.
  */
 struct tb_cfg_result tb_cfg_write_raw(struct tb_ctl *ctl, const void *buffer,
 		u64 route, u32 port, enum tb_cfg_space space,
···
  * Reads the first dword from the switches TB_CFG_SWITCH config area and
  * returns the port number from which the reply originated.
  *
- * Return: Returns the upstream port number on success or an error code on
- * failure.
+ * Return: Upstream port number on success or negative error code on failure.
  */
 int tb_cfg_get_upstream_port(struct tb_ctl *ctl, u64 route)
 {