On Mon, Apr 25, 2011 at 10:28:25AM -0700, Sarah Sharp wrote: > Random question time. :) > > Do USB device drivers have to cancel all URBs that are pending for a > device before calling usb_reset_device? Will the drivers have to wait > for the URBs to complete before resetting the device? No, not that I know of, they can reset it at any point in time, and I thought any pending urbs would be cancelled by the usb core, right? It should be easy to test this. > The specific random question I got asked by the chipset folks is: > > "Before issuing a Port Reset, is there any condition that the driver > should remove the TD associated with the device?" > > Not quite sure what to make of that, since I don't know EHCI internals. > > The second question relates to the CLEAR_TT_BUFFER request, and it only > applies to an Intel EHCI controller with a built-in rate matching hub > (RMH). The chipset folks want to know if a CLEAR_TT_BUFFER request > might be used before a port suspend or a port reset. > > It looks like the EHCI driver automatically clears the TT buffer, except > when the host controller has a Transaction Translator built into the > root hub, or we need to clear a TT buffer on an external HS hub. I > assume that means we won't clear the TT buffer for the EHCI roothub, > since this platform has a rate matching hub? Hm, I think you are right. I think that we are lucky in that very few drivers ever call usb_reset_device. thanks, greg k-h -- 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
