so, the HC clears CLF (ControlListFilled bit of the register "Command Status") immedi...

so, the HC clears CLF (ControlListFilled bit of the register "Command Status") immediately after setting it.
the ohci specs says:
"This bit is used to indicate whether there are any TDs on the Control
list. It is set by HCD whenever it adds a TD to an ED in the Control
list." [so far so good]
"When HC begins to process the head of the Control list, it checks CLF.
As long as ControlListFilled is 0, HC will not start processing the
Control list. If CLF is 1, HC will start processing the Control list and
will set ControlListFilled to 0. If HC finds a TD on the list, then HC
will set ControlListFilled to 1 causing the Control list processing to
continue. If no TD is found on the Control list, and if the HCD does not
set ControlListFilled, then ControlListFilled will still be 0 when HC
completes processing the Control list and Control list processing will
stop."

What does it mean for us? HC don't find the TD?