Hi, (replying from another PC, not sure if formatting will be broken, hopefully not) On May 23, 2011, at 7:28 PM, Alan Stern wrote: >>> Since in dummy_hcd all of this is much simpler I think that the device speed >>> should be determined by driver->speed and "which type of cable the >>> connection was made over - SS or HS". The "cable type" is exactly what the >>> module parameter is. >> >> I really don't understand this. You're going to have a module parameter >> for what type of cable is plugged in? > > It would be more accurate to say the module parameter will be used to > force the connection to run at a lower speed than the maximum possible. > This is kind of like what happens when you plug in a SuperSpeed device > using a USB-2 cable -- the connection runs at a lower speed than it > could have. if it's something like that, for sure we can have the module parameter. But plugging a USB2 gadget/function to a USB3-capable UDC/HCD should work fine. With Tatyana's patches, if we load a USB2 g_zero to dummy_hcd, enumeration will fail where it shouldn't. This has been my whole point ;-) Maybe I wasn't clear enough. >> What about the case where SuperSpeed enumeration >> fails and you have to fall back to high speed? > > If SuperSpeed enumeration fails, say because the device doesn't have > any SuperSpeed descriptors, xhci-hcd doesn't fall back to high speed, > does it? dummy-hcd should behave the same way. it should at least. Isn't that what happens between EHCI/OHCI ? HS Chirp sequencing fails, then we fall back to FullSpeed. >> It seems like you really >> need to handle both speeds and the speed fall back parameter in the same >> driver. Isn't there some other gadget driver that has a fall back to >> full or low speed when high speed enumeration fails? > > That's a property of the gadget driver, not the UDC driver. dummy-hcd > is a UDC driver (and an HCD too). USB3.0 dummy_hcd should still enumerate USB2.0 gadget drivers. -- balbi -- 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
