Re: [RFTv2 PATCH] xhci: rework cycle bit checking for new dequeue pointers

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



I don't think this works. As I understand it, ep_ring->cycle_state
contains the current cycle state at the enqueue pointer, not the
dequeue pointer (it gets updated in inc_enq() but not in inc_deq() for
transfer rings). That's the only reason we need to pull it out of the
Endpoint Context at all... because we have long since overwritten our
own software copy, when we originally enqueued the TD (and an
arbitrary amount of further ones after it).

I think if we really want to play it safe, any solution for this must
keep track of and only stop searching after both passing last_trb and
reaching hw_dequeue (taking the cycle_state off the latter), since
there might be cases where either of them could be more than one TRB
after the other. Maybe if you add another last_found variable and
depend the loop on both you could implement that in a clear way?
(Also, I'm wondering if we should just drop the code that skips whole
segments to make it simpler, since I can hardly think of any
real-world examples where a single TD would cover a whole segment.)
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [Linux Media]     [Linux Input]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [Old Linux USB Devel Archive]

  Powered by Linux