On Sun, May 20, 2018 at 02:22:27AM +0200, Florian Zumbiehl wrote: > Before I investigated how to implement this patch I just saw that s/w flow > control "didn't work", but my assumption was that that was due to buffering > latencies, not because the kernel just ignored the request. But then, > chances are a software implementation indeed wouldn't work very well anyway > for exactly that reason?!
Indeed, the deep queues might prevent a software implementation from being very useful. > > The line discipline implementation kicks in whenever IXON is set, and > > can be used as a fallback for devices where automatic hardware and > > software flow control cannot be enabled concurrently in hardware for > > example. > > Well, yeah, my guess would be that to actually make it work (well), one > would need more than that? Like, implement rate control in software to keep > the hardware buffers empty in order to achieve short reaction times? Which > one would probably want to disable though when it's not needed in order to > take advantage of the buffers? Maybe, but chances are none of this is worth the added complexity. If you need XON/XOFF you should get a device which supports it in hardware. > > While non-hardware assisted usb serial XON/XOFF is currently broken in > > that transmission would not be halted, the line discipline would still > > swallow any escape characters. > > Actually, that is required even for the pl2303, as it does not swallow the > control characters itself. Yeah, I noticed that too. Thanks, Johan -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
