On Mon, 6 May 2019, Jim Lin wrote: > USB 2.0 specification chapter 11.17.5 says "as part of endpoint halt > processing for full-/low-speed endpoints connected via a TT, the host > software must use the Clear_TT_Buffer request to the TT to ensure > that the buffer is not in the busy state". > > In our case, a full-speed speaker (ConferenceCam) is behind a high- > speed hub (ConferenceCam Connect), sometimes once we get STALL on a > request we may continue to get STALL with the folllowing requests, > like Set_Interface. > > Here we add Clear_TT_Buffer for the following Set_Interface requests > to get ACK successfully. > > Originally usb_hub_clear_tt_buffer uses urb->dev->devnum as device > address while sending Clear_TT_Buffer command, but this doesn't work > for XHCI. Why doesn't it work for xHCI? Clear-TT-Buffer is part of the USB 2.0 spec; it should work exactly the same for xHCI as for a USB-2.0 host controller. Alan Stern
