Johannes:
With Duncan away, you're the only other person I know still interested in
working on this...
Duncan's suggestions gave me some ideas for even more improvements.
Consider this:
Merge the code that frees QHs, TDs, and urbps. That eliminates
the need for the qh_remove_list and the list headers in the QHs.
Eliminate the complete_list as well. When an URB completes, just
call uhci_finish_urb() instead of uhci_add_complete(). Unlinked URBs can
be passed to uhci_finish_urb() as they get processed in the
urb_remove_list.
The processing in uhci_transfer_result() could be speeded up a
little by keeping some extra state in urbp. Keep track of the first
active TD, and scan the list of TD's starting from there instead of from
the beginning. That will be a big help especially for iso. transfers,
since it will avoid scanning the same completed TDs over and over again.
It also presents the possibility of unlinking iso. TDs as they complete,
rather than waiting for the entire URB to finish. That could be the
solution to the problem of iso. URBs that try to schedule transfers more
than 1024 frames in the future. As each TD completes, unlink it and then
see if it can be added back in to take care of a descriptor that was too
far in the future originally but is okay now.
Alan Stern
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