On Tue, Mar 19, 2002, Stephan Feder <[EMAIL PROTECTED]> wrote: > Georg Acher wrote: > > > > On Mon, Mar 18, 2002 at 12:10:31AM +0100, Stephan Feder wrote: > > > To be precise: the failures I am talking about are those that could > > > occur while talking to real devices, not errors like OOM and illegal > > > URBs (e.g. URBs with transfer_buffer=0 and transfer_buffer_length!=0). I > > > do not know in which category URBs with a bad pipe value fall. > > > > I think these failures are already well defined. The cases in which > > submit_urb immediately fails can only be "formal" failures (bad pipes, NULL > > pointers somewhere, wrong length, etc.), ie. everything that can be checked > > before actually transmitting. In these cases the return value is > > !=0 and no USB transfer was sent out on the "wire". > > > > Everything else that happens after the return of submit_urb can only be > > related to the device or the host controller itself. These failures are > > handled by calling the completion with the right urb->status. > > > > There should be absolutely no case in which submit_urb returns with !=0 and a > > completions to that URB comes later on. > > I completely agree but it is still not documented anywhere. Furthermore, > the completion handler can be (and was until recently in uhci) called > _before_ returning from submit_urb; whether the completion handler is > called before or after return from submit_urb is undefined in the > general case.
It still can be called like that, in the case of the virtual root hub atleast. It's too much work to do otherwise. But this shouldn't be an issue, everything should be setup before usb_submit_urb to be ready for the completion handler callback. If you're not, it's a race condition waiting to happen. > But that is beside the point: The question was how to handle > "non-formal" failures in the root hub. Right now they are handled > differently from failures in non-root hubs where the failure is reported > in the completion handler. Well, yes and no. In uhci atleast, it'll call the completion handler as well as returning the error from usb_submit_urb. I'm not sure if that's the best thing to do however. JE _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
