On Wed, 23 May 2018, Nicolas Boichat wrote: > The "old" enumeration scheme is considerably faster (it takes > ~294ms instead of ~439ms to get the descriptor). > > It is currently only possible to use the old scheme globally > (/sys/module/usbcore/parameters/old_scheme_first), which is not > desirable as the new scheme was introduced to increase compatibility > with more devices. > > However, in our case, we care about time-to-active for a specific > USB device (which we make the firmware for), on a specific port > (that is pogo-pin based: not a standard USB port). This new > sysfs option makes it possible to use the old scheme on a single > port only. > > Signed-off-by: Nicolas Boichat <drinkcat@xxxxxxxxxxxx> > --- > > There are other "quirks" that we could add to reduce further > enumeration time (e.g. reduce USB debounce time, reduce TRSTRCY > to 10ms instead of 50ms as used currently), but the logic is quite > similar, so it'd be good to have this reviewed first. I'm not opposed to the idea in principle, although I don't like your implementation because it breaks the original old_scheme_first parameter. Let's see what some other people think. Yours is a rather special case, because you know exactly what device will be attached to a specific port. Still, I can see that sort of thing happening in constrained and special-purpose settings. How do you arrange to set the new quirk before the device is discovered? 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
