* Arjan van de Ven <arjan@xxxxxxxxxxxxx> wrote: > On Tue, 21 Apr 2009 08:43:46 +0200 > Ingo Molnar <mingo@xxxxxxx> wrote: > > > The proper approach would be to use one of the async_synchronize*() > > facilities in kernel/async.c to properly order the opening of the > > console with device init. > > Unfortunately this is not the answer. > > First of all, USB does not use the async_* infrastructure, so it does > not do anything. [ Of course it does not. Two kernel cycles ago nothing had any async infrastructure ;-) We barely have any use of it today. But cases like this are the way to extend its use. ] > But more importantly... USB *CANNOT* do this fundamental > operation. USB does not have the capability to know when you have > seen all devices that are connected. Devices just show up a random > amount of time after you turn the power on for the bus.... there's > no "and now we've seen all" operation. Yes - and this is fundamentally true of any hotplug bus design. Nevertheless the wish has been expressed to wait for such a device to become available, in this very thread we are discussing. What i'm saying is: instead of "wait 2000 msecs, maybe it works out" hack, there should be a proper sleep+event based approach to the same. With perhaps a _timeout_ for the "no console arrived" negative case as well. (which timeout can be set to zero in the "I _know_ there's no console around".) Do you see the fundamental design difference between the two solutions? Ingo -- 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
