Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes: > On Mon, 22 Aug 2016, Bjørn Mork wrote: > >> Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes: >> >> > On Sun, 21 Aug 2016, Jiri Slaby wrote: >> > >> >> Cc: proper lists. >> >> >> >> ep->desc.bInterval seems to be 0 here. > >> > As far as I can see, this isn't possible. The usb_parse_endpoint() >> > routine in drivers/usb/core/config.c is supposed to guarantee that >> > ep->desc.bInterval is never 0. >> >> That is if it is an ISO endpoint, right? > > I can't tell; the bug report doesn't say. However, ep->desc.bInterval > is ignored for bulk and control endpoints, so it must be either > isochronous or interrupt. So what if the endpoint is not isochronous or interrupt here? >> Maybe I misunderstand something fundamental, but the "||" strikes me as >> odd here: >> >> as->urb->stream_id = stream_id; >> if (uurb->type == USBDEVFS_URB_TYPE_ISO || >> ps->dev->speed == USB_SPEED_HIGH) >> as->urb->interval = 1 << min(15, ep->desc.bInterval - 1); >> else >> as->urb->interval = ep->desc.bInterval; >> as->urb->context = as; > > No, that's right (mostly -- we really should check for ps->dev->speed >>= USB_SPEED_SUPER as well as == USB_SPEED_HIGH). > >> Typo? > > USB uses two different encodings for endpoint intervals. The second > encoding above just gives the interval in frames; this is used for low- > and full-speed interrupt endpoints. The first encoding above is > exponential (it gives n where the actual interval is 2^(n-1) frames or > microframes); this is used for all isochronous endpoints and for > high-speed (or SuperSpeed etc.) interrupt endpoints. OK, I am still puzzled: Won't the code I quoted above do the shift for *any* uurb->type and endpoint type? There doesn't seem to be any test for isochronous or interrupt endpoint around it? Bjørn -- 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
