On Wed, 3 Jul 2013, Ming Lei wrote: > >> Yes, that is the change tasklet is bringing, so looks we need to find a way > >> to distinguish streaming-on from underrun when stream->td_list becomes > >> empty in iso_stream_schedule(). > > > > The difference will be the URB_ISO_ASAP flag. The flag should be set > > in the first URB of a new stream. It should not be set in any other > > URBs, unless the client driver doesn't care about losing > > synchronization when an underrun occurs. > > So sounds a better name for the flag should be URB_ISO_STREAM_ON, :-) I agree, but the existing name is already exposed to userspace in include/uapi/linux/usbdevice_fs.h. We could change the internal name while leaving the external name the same, but that would be confusing. (URB_ISO_ASAP used to mean that the HCD was responsible for scheduling the URB, and if the flag wasn't set then the value of urb->start_frame would be used directly. This doesn't make sense, because drivers should not be in charge of URB scheduling -- HCDs should take care of it. So I have felt free to alter the flag's meaning.) > Also looks drivers need fix for the API change. I don't know if any drivers will need to be fixed. I suspect many of them simply set URB_ISO_ASAP on all their URBs. Clemens has already added a fix for the snd-usb-audio driver. Alan Stern -- 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
