Index: uspace/drv/uhci-hcd/hw_struct/queue_head.h
===================================================================
--- uspace/drv/uhci-hcd/hw_struct/queue_head.h	(revision 4c7055473203b4ece7dceab3eea42dabe7f40cd3)
+++ uspace/drv/uhci-hcd/hw_struct/queue_head.h	(revision 9d2d444d3b59436c06a1f40efb0311a036ac3f9f)
@@ -37,8 +37,12 @@
 
 #include "link_pointer.h"
+#include "transfer_descriptor.h"
 #include "utils/malloc32.h"
 
+/** This structure is defined in UHCI design guide p. 31 */
 typedef struct queue_head {
+	/** Pointer to the next entity (another QH or TD */
 	volatile link_pointer_t next;
+	/** Pointer to the contained entities (execution controlled by vertical flag*/
 	volatile link_pointer_t element;
 } __attribute__((packed)) qh_t;
@@ -63,10 +67,8 @@
  * @param[in] pa Physical address of the next queue head.
  *
- * Adds proper flag. If the pointer is NULL or terminal, sets next to terminal
- * NULL.
+ * Adds proper flag. If the pointer is NULL, sets next to terminal NULL.
  */
 static inline void qh_set_next_qh(qh_t *instance, qh_t *next)
 {
-	/* Address is valid and not terminal */
 	uint32_t pa = addr_to_phys(next);
 	if (pa) {
@@ -82,10 +84,10 @@
  * @param[in] pa Physical address of the TD structure.
  *
- * Adds proper flag. If the pointer is NULL or terminal, sets element
- * to terminal NULL.
+ * Adds proper flag. If the pointer is NULL, sets element to terminal NULL.
  */
-static inline void qh_set_element_td(qh_t *instance, uint32_t pa)
+static inline void qh_set_element_td(qh_t *instance, td_t *td)
 {
-	if (pa && ((pa & LINK_POINTER_TERMINATE_FLAG) == 0)) {
+	uint32_t pa = addr_to_phys(td);
+	if (pa) {
 		instance->element = LINK_POINTER_TD(pa);
 	} else {
@@ -93,5 +95,4 @@
 	}
 }
-
 #endif
 /**
Index: uspace/drv/uhci-hcd/hw_struct/transfer_descriptor.c
===================================================================
--- uspace/drv/uhci-hcd/hw_struct/transfer_descriptor.c	(revision 4c7055473203b4ece7dceab3eea42dabe7f40cd3)
+++ uspace/drv/uhci-hcd/hw_struct/transfer_descriptor.c	(revision 9d2d444d3b59436c06a1f40efb0311a036ac3f9f)
@@ -77,5 +77,6 @@
 
 	instance->status = 0
-	    | ((err_count & TD_STATUS_ERROR_COUNT_MASK) << TD_STATUS_ERROR_COUNT_POS)
+	    | ((err_count & TD_STATUS_ERROR_COUNT_MASK)
+	        << TD_STATUS_ERROR_COUNT_POS)
 	    | (low_speed ? TD_STATUS_LOW_SPEED_FLAG : 0)
 	    | (iso ? TD_STATUS_ISOCHRONOUS_FLAG : 0)
@@ -89,6 +90,8 @@
 	    | (((size - 1) & TD_DEVICE_MAXLEN_MASK) << TD_DEVICE_MAXLEN_POS)
 	    | (toggle ? TD_DEVICE_DATA_TOGGLE_ONE_FLAG : 0)
-	    | ((target.address & TD_DEVICE_ADDRESS_MASK) << TD_DEVICE_ADDRESS_POS)
-	    | ((target.endpoint & TD_DEVICE_ENDPOINT_MASK) << TD_DEVICE_ENDPOINT_POS)
+	    | ((target.address & TD_DEVICE_ADDRESS_MASK)
+	        << TD_DEVICE_ADDRESS_POS)
+	    | ((target.endpoint & TD_DEVICE_ENDPOINT_MASK)
+	        << TD_DEVICE_ENDPOINT_POS)
 	    | ((pid & TD_DEVICE_PID_MASK) << TD_DEVICE_PID_POS);
 
@@ -114,5 +117,5 @@
 	assert(instance);
 
-	/* this is hc internal error it should never be reported */
+	/* This is hc internal error it should never be reported. */
 	if ((instance->status & TD_STATUS_ERROR_BIT_STUFF) != 0)
 		return EAGAIN;
@@ -123,18 +126,18 @@
 		return EBADCHECKSUM;
 
-	/* hc does not end transaction on these, it should never be reported */
+	/* HC does not end transactions on these, it should never be reported */
 	if ((instance->status & TD_STATUS_ERROR_NAK) != 0)
 		return EAGAIN;
 
-	/* buffer overrun or underrun */
+	/* Buffer overrun or underrun */
 	if ((instance->status & TD_STATUS_ERROR_BUFFER) != 0)
 		return ERANGE;
 
-	/* device babble is something serious */
+	/* Device babble is something serious */
 	if ((instance->status & TD_STATUS_ERROR_BABBLE) != 0)
 		return EIO;
 
-	/* stall might represent err count reaching zero or stall response from
-	 * the device, is err count reached zero, one of the above is reported*/
+	/* Stall might represent err count reaching zero or stall response from
+	 * the device. If err count reached zero, one of the above is reported*/
 	if ((instance->status & TD_STATUS_ERROR_STALLED) != 0)
 		return ESTALL;
Index: uspace/drv/uhci-hcd/hw_struct/transfer_descriptor.h
===================================================================
--- uspace/drv/uhci-hcd/hw_struct/transfer_descriptor.h	(revision 4c7055473203b4ece7dceab3eea42dabe7f40cd3)
+++ uspace/drv/uhci-hcd/hw_struct/transfer_descriptor.h	(revision 9d2d444d3b59436c06a1f40efb0311a036ac3f9f)
@@ -40,48 +40,53 @@
 #include "link_pointer.h"
 
-/** UHCI Transfer Descriptor */
+/** Transfer Descriptor, defined in UHCI design guide p. 26 */
 typedef struct transfer_descriptor {
+	/** Pointer to the next entity (TD or QH) */
 	link_pointer_t next;
 
+	/** Status doubleword */
 	volatile uint32_t status;
 #define TD_STATUS_RESERVED_MASK 0xc000f800
-#define TD_STATUS_SPD_FLAG ( 1 << 29 )
-#define TD_STATUS_ERROR_COUNT_POS ( 27 )
-#define TD_STATUS_ERROR_COUNT_MASK ( 0x3 )
-#define TD_STATUS_LOW_SPEED_FLAG ( 1 << 26 )
-#define TD_STATUS_ISOCHRONOUS_FLAG ( 1 << 25 )
-#define TD_STATUS_IOC_FLAG ( 1 << 24 )
+#define TD_STATUS_SPD_FLAG         (1 << 29)
+#define TD_STATUS_ERROR_COUNT_POS 27
+#define TD_STATUS_ERROR_COUNT_MASK 0x3
+#define TD_STATUS_LOW_SPEED_FLAG   (1 << 26)
+#define TD_STATUS_ISOCHRONOUS_FLAG (1 << 25)
+#define TD_STATUS_IOC_FLAG         (1 << 24)
 
-#define TD_STATUS_ERROR_ACTIVE ( 1 << 23 )
-#define TD_STATUS_ERROR_STALLED ( 1 << 22 )
-#define TD_STATUS_ERROR_BUFFER ( 1 << 21 )
-#define TD_STATUS_ERROR_BABBLE ( 1 << 20 )
-#define TD_STATUS_ERROR_NAK ( 1 << 19 )
-#define TD_STATUS_ERROR_CRC ( 1 << 18 )
-#define TD_STATUS_ERROR_BIT_STUFF ( 1 << 17 )
-#define TD_STATUS_ERROR_RESERVED ( 1 << 16 )
+#define TD_STATUS_ERROR_ACTIVE    (1 << 23)
+#define TD_STATUS_ERROR_STALLED   (1 << 22)
+#define TD_STATUS_ERROR_BUFFER    (1 << 21)
+#define TD_STATUS_ERROR_BABBLE    (1 << 20)
+#define TD_STATUS_ERROR_NAK       (1 << 19)
+#define TD_STATUS_ERROR_CRC       (1 << 18)
+#define TD_STATUS_ERROR_BIT_STUFF (1 << 17)
+#define TD_STATUS_ERROR_RESERVED  (1 << 16)
 #define TD_STATUS_ERROR_POS 16
-#define TD_STATUS_ERROR_MASK ( 0xff )
+#define TD_STATUS_ERROR_MASK 0xff
 
 #define TD_STATUS_ACTLEN_POS 0
 #define TD_STATUS_ACTLEN_MASK 0x7ff
 
+	/* double word with USB device specific info */
 	volatile uint32_t device;
 #define TD_DEVICE_MAXLEN_POS 21
-#define TD_DEVICE_MAXLEN_MASK ( 0x7ff )
-#define TD_DEVICE_RESERVED_FLAG ( 1 << 20 )
-#define TD_DEVICE_DATA_TOGGLE_ONE_FLAG ( 1 << 19 )
+#define TD_DEVICE_MAXLEN_MASK 0x7ff
+#define TD_DEVICE_RESERVED_FLAG        (1 << 20)
+#define TD_DEVICE_DATA_TOGGLE_ONE_FLAG (1 << 19)
 #define TD_DEVICE_ENDPOINT_POS 15
-#define TD_DEVICE_ENDPOINT_MASK ( 0xf )
+#define TD_DEVICE_ENDPOINT_MASK 0xf
 #define TD_DEVICE_ADDRESS_POS 8
-#define TD_DEVICE_ADDRESS_MASK ( 0x7f )
+#define TD_DEVICE_ADDRESS_MASK 0x7f
 #define TD_DEVICE_PID_POS 0
-#define TD_DEVICE_PID_MASK ( 0xff )
+#define TD_DEVICE_PID_MASK 0xff
 
+	/** Pointer(physical) to the beginning of the transaction's buffer */
 	volatile uint32_t buffer_ptr;
 
-	/* there is 16 bytes of data available here, according to UHCI
-	 * Design guide, according to linux kernel the hardware does not care,
-	 * it just needs to be aligned, we don't use it anyway
+	/* According to UHCI design guide, there is 16 bytes of
+	 * data available here.
+	 * 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;