[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Bug 1859378] Re: xhci Control Transfer requiring a Status TRB before st
Benjamin David Lunt
[Bug 1859378] Re: xhci Control Transfer requiring a Status TRB before starting transfer
Mon, 13 Jan 2020 00:30:07 -0000
Removing this check will indeed require a bit of a re-write. The way
the code is now, the transfer expects a SETUP packet to be first. If
you remove the check I ask about above, will the next transfer show that
it is the STATUS packet? If so, then the check at line 1696 will indeed
catch and not allow the STATUS packet to be accepted.
A little more work might need to be done to remove this check.
It is just a request.
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
xhci Control Transfer requiring a Status TRB before starting transfer
Status in QEMU:
This may not necessarily be a bug, but more of a change.
A little background may need to be in order.
With all USB Control transfers, there is a SETUP transfer, zero or
more DATA transfers, and if successful, a STATUS transfer. This
STATUS transfer is used to indicate to the recipient that the previous
transfers were successful. For example, in a CONTROL IN transfer, the
host sends a SETUP packet to the device, receives zero or more DATA
packets, and then on successful transfer, the HOST sends the STATUS
packet indicating to the device that all was received.
If no DATA packets are received, the HOST is not to send a STATUS
packet. This could be due to a STALL or other error.
With this in mind, the STATUS transfer, in this case an xHCI STATUS
TRB, may not even be on the transfer ring yet. The HOST software may
be waiting for a successful transfer before it submits the STATUS
However, if you look at the test at line 1701
the current code will not start the CONTROL transfer at all if it
doesn't see that STATUS TRB on the ring.
In my opinion, this is in error. It is not required that a STATUS TRB
be on the ring to start the CONTROL transfer. This STATUS TRB can be
placed on the ring after a successful SETUP and zero or more DATA
transfers followed by a ring to the door bell. Then after a
successful transfer to this point, placing this STATUS TRB on the ring
and another ring to the door bell.
In my opinion, the check at line 1701 should be removed.
To manage notifications about this bug go to: