diff --git a/docs/develop/busses/usb/xhci.txt b/docs/develop/busses/usb/xhci.txt
deleted file mode 100644
index 9c8d79cc51..0000000000
--- a/docs/develop/busses/usb/xhci.txt
+++ /dev/null
@@ -1,47 +0,0 @@
-anyway, here's the summary of XHCI stuff:
-- XHCI operates in units of "TRBs", which consist of a pointer and two 32-bit
-  fields holding varying types of data based on the TRB type. A "normal" type
-  TRB usually has a pointer to a physical buffer and then in one of the fields,
-  an indicator of how many bytes are stored there
-- XHCI concept of "rings" is not, as you might expect, circular buffers.
-  Instead, it uses "Link TRBs", that is, a TRB in which the pointer field
-  points to the next place the hardware should read TRBs from, and it will do
-  so until hitting another Link TRB, etc. So it is in fact more like a linked
-  list. This allows easier management of the event queue, there is no need for
-  a fixed size ring, managing edge cases when the buffer wraps around, etc.
-
-The way we handle transfers in the XHCI driver is:
-- We allocate a "ring" of a small fixed amount for each endpoint (currently,
-  defined as XHCI_MAX_TRANSFERS*2+1, because we need 2 TRBs on the "ring" for
-  each transfer, and 1 at the end for the link to go back to the beginning)
--  When the stack calls SubmitTransfer(), we allocate a new run of TRBs to
-  handle this transfer, and populate them with all the data. Then we insert one
-  Link TRB on the endpoint ring pointing to the first in the "transfer ring" we
-  just made, a link TRB at the end of the "transfer ring" pointing back to the
-  "endpoint ring", and then an "Event Status" TRB on the "endpoint ring" which
-  tells the XHCI to send an event back to us to tell us the transfer is done
-- For easier tracking, the driver also keeps a TD (transfer descriptor), which
-  is a sideband structure not sent to the hardware, but used to keep track of
-  the TRBs in a given endpoint ring.
-
-So under normal circumstances (i.e. all transfers submitted are successful), we
-will get back only "Event" TRBs generated by the "Event Data" TRBs from the
-"endpoint ring"s, and these will tell us what transfer they correspond to, we
-will notify it as successful, and all is well.
-
-If a transfer fails, then XHCI will generate an event that does *not*
-correspond to an Event Status TRB (src/add-ons/kernel/busses/usb/xhci.cpp#L2372).
-The pointer field in this TRB will point to the TRB that caused XHCI to
-generate the event (i.e. the failed TRB), and so we look through the transfers
-in progress on this endpoint and try to find which one corresponds to that TRB.
-
-However, it seems in your case we are failing to find it, and so we get a
-"TRB xxxx was not found in the endpoint!"
-Most likely this TRB is on the "endpoint ring" itself. However as noted before,
-only 2 TRBs for each transfer are actually on the endpoint ring: the Link TRB
-going to the "transfer ring", and the Event Data TRB telling XHCI to fire an
-interrupt.
-
-Valid Link TRBs should never fail to execute; and to my knowledge Event Data
-TRBs should not either.
-
diff --git a/src/add-ons/kernel/busses/usb/xhci.cpp b/src/add-ons/kernel/busses/usb/xhci.cpp
index 600e9ecd19..ce841c41f5 100644
--- a/src/add-ons/kernel/busses/usb/xhci.cpp
+++ b/src/add-ons/kernel/busses/usb/xhci.cpp
@@ -2467,6 +2467,7 @@ XHCI::HandleTransferComplete(xhci_trb* trb)
 		  (flags & TRB_3_EVENT_DATA_BIT), completionCode, transferred);
 
 	if ((flags & TRB_3_EVENT_DATA_BIT) == 0) {
+		// This should only occur under error conditions.
 		TRACE("got an interrupt for a non-Event Data TRB!\n");
 		remainder = transferred;
 		transferred = -1;
diff --git a/src/add-ons/kernel/busses/usb/xhci.h b/src/add-ons/kernel/busses/usb/xhci.h
index 6c3455df7c..7098d4f272 100644
--- a/src/add-ons/kernel/busses/usb/xhci.h
+++ b/src/add-ons/kernel/busses/usb/xhci.h
@@ -25,6 +25,9 @@ struct xhci_endpoint;
 class XHCIRootHub;
 
 
+/* Each transfer requires 2 TRBs on the endpoint "ring" (one for the link TRB,
+ * and one for the Event Data TRB), plus one more at the end for the link TRB
+ * to the start. */
 #define XHCI_ENDPOINT_RING_SIZE	(XHCI_MAX_TRANSFERS * 2 + 1)