tree 1537e1fb6ca465b01b4e7032081c0e5533b0510b
parent d1f114d12bb4db3147e1b1342ae31083c5a79c84
author Alan Stern <stern@rowland.harvard.edu> 1211317150 -0400
committer Greg Kroah-Hartman <gregkh@suse.de> 1212094744 -0700

USB: EHCI: fix bug in Iso scheduling

This patch (as1098) changes the way ehci-hcd schedules its periodic
Iso transfers.  That the current scheduling code is wrong is clear on
the face of it: Sometimes it returns -EL2NSYNC (meaning that an URB
couldn't be scheduled because it was submitted too late), but it does
this even when the URB_ISO_ASAP flag is set (meaning the URB should be
scheduled as soon as possible).

The new code properly implements as-soon-as-possible scheduling,
assigning the next unexpired slot as the URB's starting point.  It
also is more careful about checking for Iso URB completion: It doesn't
bother to check for activity during frames that are already over,
and it allows for the possibility that some of the URB's packets may
have raced the hardware when they were submitted and so never got used
(the packet status is set to -EXDEV).

This fixes problems several people have experienced with USB video
applications.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>