On Wed, May 22, 2024 at 01:41:42AM +0000, Thinh Nguyen wrote: > On Wed, May 22, 2024, Michael Grzeschik wrote: > > On Fri, May 17, 2024 at 01:44:05AM +0000, Thinh Nguyen wrote: > > > For isoc endpoint IN, yes. If the host requests for isoc data IN while > > > no TRB is prepared, then the controller will automatically send 0-length > > > packet respond. > > > > Perfect! This will help a lot and will make active queueing of own > > zero-length requests run unnecessary. > > Yes, if we rely on the current start/stop isoc transfer scheme for UVC, > then this will work. You shouldn't rely on this behavior. Other device controllers might not behave this way; they might send no packet at all to the host (causing a USB protocol error) instead of sending a zero-length packet. On the other hand, it may not make any difference. The host's UVC driver most likely won't care about the difference between no packet and a 0-length packet. :-) Alan Stern
