On Thu, 4 Jul 2013, Alan Stern wrote: > On Thu, 4 Jul 2013, Ming Lei wrote: > > > >> If so, your coming change may break ABI because as you described > > >> that "the flag should be set in the first URB of a new stream", but > > >> some user-space drivers may not set it before. Even USB audio driver > > >> doesn't set it in current -next tree. I had some more ideas about this. Instead of requiring drivers to set URB_ISO_ASAP on just the first URB of an isochronous stream, we could ask drivers to call usb_reset_endpoint() between streams. This would tell the HCD that the next URB marks the start of a new stream, with no need for a special flag. Another possibility, which would be even simpler, is for HCDs to assume that if the endpoint's queue has been empty for more than 100 ms then a new stream is starting. Then drivers wouldn't have to do anything special at all. (Unless they are stopping and restarting streams very rapidly, in which case something like usb_reset_endpoint() would be necessary.) What do you think? 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
