Index: uspace/drv/uhci-hcd/batch.c
===================================================================
--- uspace/drv/uhci-hcd/batch.c	(revision 67352d2ce57d0bbae9f4f2b0a767afb56ae158b6)
+++ uspace/drv/uhci-hcd/batch.c	(revision eb0dc587ae7da417930cae6d0a65bb86fea11513)
@@ -319,5 +319,5 @@
 		++packet;
 	}
-	instance->tds[packet - 1].status |= TD_STATUS_IOC_FLAG;
+	td_set_ioc(&instance->tds[packet - 1]);
 	device_keeper_set_toggle(instance->manager, instance->target, toggle);
 }
@@ -371,6 +371,5 @@
 	    0, 1, false, low_speed, instance->target, status_stage, NULL, NULL);
 
-
-	instance->tds[packet].status |= TD_STATUS_IOC_FLAG;
+	td_set_ioc(&instance->tds[packet]);
 	usb_log_debug2("Control last TD status: %x.\n",
 	    instance->tds[packet].status);
Index: uspace/drv/uhci-hcd/uhci_struct/transfer_descriptor.c
===================================================================
--- uspace/drv/uhci-hcd/uhci_struct/transfer_descriptor.c	(revision 67352d2ce57d0bbae9f4f2b0a767afb56ae158b6)
+++ uspace/drv/uhci-hcd/uhci_struct/transfer_descriptor.c	(revision eb0dc587ae7da417930cae6d0a65bb86fea11513)
@@ -44,5 +44,5 @@
  * @param[in] size Size of data source.
  * @param[in] toggle Value of toggle bit.
- * @param[in] iso True if TD is for Isochronous transfer.
+ * @param[in] iso True if TD represents Isochronous transfer.
  * @param[in] low_speed Target device's speed.
  * @param[in] target Address and endpoint receiving the transfer.
@@ -51,4 +51,12 @@
  * @param[in] next Net TD in transaction.
  * @return Error code.
+ *
+ * Uses a mix of supplied and default values.
+ * Implicit values:
+ *  - all TDs have vertical flag set (makes transfers to endpoints atomic)
+ *  - in the error field only active it is set
+ *  - if the packet uses PID_IN and is not isochronous SPD is set
+ *
+ * Dumps 8 bytes of buffer if PID_SETUP is used.
  */
 void td_init(td_t *instance, int err_count, size_t size, bool toggle, bool iso,
@@ -94,5 +102,5 @@
 	if (pid == USB_PID_SETUP) {
 		usb_log_debug("SETUP BUFFER: %s\n",
-			usb_debug_str_buffer(buffer, 8, 8));
+		    usb_debug_str_buffer(buffer, 8, 8));
 	}
 }
@@ -128,4 +136,8 @@
 }
 /*----------------------------------------------------------------------------*/
+/** Print values in status field (dw1) in a human readable way.
+ *
+ * @param[in] instance TD structure to use.
+ */
 void td_print_status(td_t *instance)
 {
Index: uspace/drv/uhci-hcd/uhci_struct/transfer_descriptor.h
===================================================================
--- uspace/drv/uhci-hcd/uhci_struct/transfer_descriptor.h	(revision 67352d2ce57d0bbae9f4f2b0a767afb56ae158b6)
+++ uspace/drv/uhci-hcd/uhci_struct/transfer_descriptor.h	(revision eb0dc587ae7da417930cae6d0a65bb86fea11513)
@@ -45,5 +45,4 @@
 
 	volatile uint32_t status;
-
 #define TD_STATUS_RESERVED_MASK 0xc000f800
 #define TD_STATUS_SPD_FLAG ( 1 << 29 )
@@ -70,5 +69,4 @@
 
 	volatile uint32_t device;
-
 #define TD_DEVICE_MAXLEN_POS 21
 #define TD_DEVICE_MAXLEN_MASK ( 0x7ff )
@@ -85,6 +83,6 @@
 
 	/* there is 16 bytes of data available here, according to UHCI
-	 * Design guide, according to linux kernel the hardware does not care
-	 * we don't use it anyway
+	 * Design guide, according to linux kernel the hardware does not care,
+	 * it just needs to be aligned, we don't use it anyway
 	 */
 } __attribute__((packed)) td_t;
@@ -97,12 +95,24 @@
 int td_status(td_t *instance);
 
+void td_print_status(td_t *instance);
+/*----------------------------------------------------------------------------*/
+/** Helper function for parsing actual size out of TD.
+ *
+ * @param[in] instance TD structure to use.
+ * @return Parsed actual size.
+ */
 static inline size_t td_act_size(td_t *instance)
 {
 	assert(instance);
-	return
-	    ((instance->status >> TD_STATUS_ACTLEN_POS) + 1)
-	    & TD_STATUS_ACTLEN_MASK;
+	const uint32_t s = instance->status;
+	return ((s >> TD_STATUS_ACTLEN_POS) + 1) & TD_STATUS_ACTLEN_MASK;
 }
-
+/*----------------------------------------------------------------------------*/
+/** Checks whether less than max data were recieved and packet is marked as SPD.
+ *
+ * @param[in] instance TD structure to use.
+ * @return True if packet is short (less than max bytes and SPD set), false
+ *     otherwise.
+ */
 static inline bool td_is_short(td_t *instance)
 {
@@ -114,12 +124,21 @@
 	    (instance->status | TD_STATUS_SPD_FLAG) && act_size < max_size;
 }
-
+/*----------------------------------------------------------------------------*/
+/** Helper function for parsing value of toggle bit.
+ *
+ * @param[in] instance TD structure to use.
+ * @return Toggle bit value.
+ */
 static inline int td_toggle(td_t *instance)
 {
 	assert(instance);
-	return ((instance->device & TD_DEVICE_DATA_TOGGLE_ONE_FLAG) != 0)
-	    ? 1 : 0;
+	return (instance->device & TD_DEVICE_DATA_TOGGLE_ONE_FLAG) ? 1 : 0;
 }
-
+/*----------------------------------------------------------------------------*/
+/** Helper function for parsing value of active bit
+ *
+ * @param[in] instance TD structure to use.
+ * @return Active bit value.
+ */
 static inline bool td_is_active(td_t *instance)
 {
@@ -127,6 +146,15 @@
 	return (instance->status & TD_STATUS_ERROR_ACTIVE) != 0;
 }
-
-void td_print_status(td_t *instance);
+/*----------------------------------------------------------------------------*/
+/** Helper function for setting IOC bit.
+ *
+ * @param[in] instance TD structure to use.
+ */
+static inline void td_set_ioc(td_t *instance)
+{
+	assert(instance);
+	instance->status |= TD_STATUS_IOC_FLAG;
+}
+/*----------------------------------------------------------------------------*/
 #endif
 /**