On 02/04/14 20:10, Sarah Sharp wrote:
And there's code in the xHCI driver to ignore the second successful
event. See ep->last_td_was_short. Yes, this is a slight race
condition, and we should wait for the successful event. However, we
have not seen any issues with this race condition.
Hi,
Some comments from the side-line:
I've observed some XHCI controllers sending special case events, like
IO-errors for ISOCHRONOUS endpoints, out of order. In not sure if the
XHCI specification is clear about this, or not, that when you have bunch
of TD's on an endpoint, you should not receive the completion event for
the next timeslot / TD, before receiving the IO-error for the previous
failed TRB/TD. I'm not sure what tests HW guys are doing these days
regarding XHCI. This has been observed during driver development of
FreeBSD's XHCI driver a long time ago, and I though I'd mention it for
you guys.
--HPS
FreeBSD's XHCI driver:
http://svnweb.freebsd.org/base/head/sys/dev/usb/controller/xhci.c?view=markup
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