On Thu, Sep 24, 2015 at 10:17:19AM -0400, Alan Stern wrote: > However, none of this answers the question of why you can use both > cards on a different machine but not on yours. It comes down to the > implementations of the xHCI controller chips. In USB-3, bandwidth > allocation is handled by firmware running on the controller, not by the > operating system's driver. The driver presents a series of endpoints > with all their bandwidth requirements to the controller, and the > controller either accepts it or rejects it. OK, I feared as much. The other machine also has an Intel controller, but as far as I know, a newer one (and the PCI ID is different -- 8086:9cb1). > It doesn't give any explanation for its decision, and as far as I know, it > doesn't provide any information about the details of how it allocates the > bandwidth. I thought I saw something in the xHCI spec about enumerating the bandwidth domains to try to get some more insight in what the topology looks like, but I guess I misunderstood it? (It all wasn't very clear to me.) I assume there's no way I can lie to the chip? Like, if I know for a fact that the card will send less data than the alternate claims (like, I'm using a video mode that will require only a few hundred megabits/second in practice, but even the lowest alternate claims >1 Gbit/sec). /* Steinar */ -- Homepage: http://www.sesse.net/ -- 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
