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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>
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Alan Stern
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Greg Kroah-Hartman
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May 29, 2008
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