On Mon, Apr 27, 2020 at 10:47 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > > On Mon, Apr 27, 2020 at 9:51 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > > > > On Fri, Apr 24, 2020 at 9:36 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > > > > > > On Fri, Apr 10, 2020 at 2:29 AM Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > > > On Thu, 9 Apr 2020, Andrey Konovalov wrote: > > > > > > > > > Hi Alan and Greg, > > > > > > > > > > I've been thinking about what kind of features raw-gadget might be > > > > > missing, that would allow more flexibility in emulating USB devices. > > > > > One of the things that is currently missing is halting endpoints. > > > > > Adding this functionality seems to be fairly easy, but it's unclear to > > > > > me how to test it. Any suggestions? > > > > > > > > You should use the usbtest driver along with the testusb program in > > > > tools/usb. Of course, to do it you will need a userspace driver for > > > > raw-gadget. usbtest works best with gadget-zero, but it can be used > > > > (in degraded form) with any USB device. > > > > > > Hi Alan, > > > > > > I've started working on a test suite for raw-gadget based on the > > > usbtest module as you suggested and have a few questions: > > > > Another question, which actually seems to be a major problem. > > > > It looks like automatic endpoint selection based on required features > > doesn't work in raw-gadget. The way it tries to do that is iterating > > over the list of available endpoints and finding one that has the > > right direction and transfer type. But it seems that the right way to > > do that (like it's done in usb_ep_autoconfig()) is to also patch the > > bEndpointAddress field of the endpoint descriptor. > > > > Currently with raw-gadget the endpoints are supposed to be enabled > > after a set_configuration/set_interface request from the host, so it's > > too late to patch the endpoint descriptor (the one that was sent to > > the host during enumeration). I'm guessing that sending one endpoint > > descriptor during enumeration and then using a different one (with > > patched bEndpointAddress) to set ep->desc before doing usb_ep_enable() > > won't work (as there's going to be mismatch in endpoint addresses > > between the host and the UDC), right? > > > > I wonder what we can do about that. It seems that we actually need to > > parse the descriptors and figure out the right endpoints before the > > enumeration starts. > > Or maybe somehow expose all endpoints and their features (like > GadgetFS) and let userspace put proper addresses into endpoint > descriptors before enumeration starts. I think this is the way to go, giving the userspace maximum control over what's going on. Seems not too hard to implement too. The only part that is not clear to me is how to figure out the endpoint address that a particular UDC endpoint expects to have. Most of the time endpoints are named as something like "ep1in" or "ep2out", and AFAIU the number in the endpoint name is the address. However net2280 seems to have weird endpoint names "ep-a", "ep-b", etc. Looking at usb_ep_autoconfig_ss(), those endpoints supposedly have sequential addresses starting from 1 (for each in/out type). But then in the GadgetFS example [1] e.g. "ep-a" corresponds to address 7, which I don't understand. My guess is that this is done to handle both dummy_udc and net2280 in a single if case, but I'm not sure. [1] http://www.linux-usb.org/gadget/usb.c
