Hi, On Tue, May 24, 2011 at 08:53:15AM +0300, Tanya Brokhman wrote: > > > > > > 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. > > > > I guess not. I thought Tatyana said she was working to fix that bug... > > This bug is fixed with the module parameter. When dummy_hcd is loaded it > registers 2 root hubs: HS & SS but unless the is_super_speed parameter is > true, the device will be connected to the HS hub. This way when loading HS > g_zero it enumerates under HS root hub successfully. > Note that if load SS gadget without setting is_super_speed=true for dummy > hcd, it will also enumerate under HS hub! This is basically a way to test > that SS devices are backward compatible. but you also need to make sure that HS gadget enumerates on SS host. I don't agree that the module parameter is the only option. > > > >> 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. > > > > That's a failure in initialization, not a failure in enumeration. > > > > There are two reasons why the HS chirp might fail: the device doesn't > > support high speed operation or hardware errors prevent the chirp from > > working. With dummy-hcd there are no hardware errors (because there's > > no hardware). > > > > As for whether or not the device supports high-speed or SuperSpeed > > operation, that's determined by the usb_gadget_driver->speed field. If > > the field doesn't specify SuperSpeed then dummy-hcd should connect the > > gadget to the USB-2 root hub rather than the USB-3 root hub. Isn't > > that what Tatyana's patch does? It contains a line saying: > > > > dum->gadget.speed = driver->speed; > > You're right. This is exactly what is done with a small update: if > is_super_speed=false the gadget will connect to a USB2 root hub even if > driver->speed=USB_SPEED_SUPER. In that case dum->gadget.speed will be set to > USB_SPEED_HIGH. The code that sets this now is: > if (mod_data.is_super_speed) > dum->gadget.speed = driver->speed; > else > dum->gadget.speed = min((u8)USB_SPEED_HIGH, ok ok, I took a closer look at the original patches and you're changing drivers->speed to super before converting the gadget drivers to superspeed. That's what's making enumeration fail on all those guys. > > > >> 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. > > > > Yes, certainly it should. If it doesn't, that's a bug, not a design > > error. > > > > This version of dummy_hcd enumerates HS devices without any issues. that's not what I saw, but then again, maybe you changed driver->speed to super and didn't provide superspeed descriptors. -- balbi
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