Hi Heinrich, [email protected] wrote on Mon, 7 Aug 2023 11:29:08 +0200:
> On 04.08.23 21:14, Miquel Raynal wrote: > > At some point when trying to use USB gadgets, two situations may arise > > and lead to a failure. Either the UDC (USB Device Controller) is not > > available at all (not described or not probed) or the UDC is already in > > use. For instance, as the USB Ethernet gadget remains bound to the UDC, > > the use of any other USB gadget (fastboot, dfu, etc) *after* will always > > fail with the "couldn't find an available UDC" error. > > Are the UDCs real devices or only logical ones? In this context there is a real device behind. But UDC is also the name for kind of an interface for gadget drivers. In theory, on USB device controller could expose several different functions. > If they are only logical ones, can we generate new ones on the fly? In general, it's not impossible, but it's not supported at all in U-Boot (and for a good reason: it would be way too complex to handle) and I think even in Linux, it's possible, but possibly only using configfs (not 100% sure on that one). > > Let's give a more helpful message by making a difference between the two > > cases. Let's also hint people who would get this error and grep it into > > the sources a better explanation of what's wrong with their workflow. > > > > Signed-off-by: Miquel Raynal <[email protected]> > > --- > > > > While doing this I really wanted to add "much more" error comments but I > > faced another reality: often the messages are there but use > > pr_err/log_err which is actually silenced by default with LOGLEVEL=3, so > > I consider this unnecessary, as decreasing the loglevel will make these > > messages appear. I would have expected errors to be displayed, but I > > understand it makes the binaries even bigger. > > --- > > drivers/usb/gadget/udc/udc-core.c | 13 ++++++++++++- > > 1 file changed, 12 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/usb/gadget/udc/udc-core.c > > b/drivers/usb/gadget/udc/udc-core.c > > index 7f73926cb3e..30f6d73f36e 100644 > > --- a/drivers/usb/gadget/udc/udc-core.c > > +++ b/drivers/usb/gadget/udc/udc-core.c > > @@ -323,6 +323,7 @@ err1: > > int usb_gadget_probe_driver(struct usb_gadget_driver *driver) > > { > > struct usb_udc *udc = NULL; > > + unsigned int udc_count = 0; > > int ret; > > > if (!driver || !driver->bind || !driver->setup) > > @@ -330,12 +331,22 @@ int usb_gadget_probe_driver(struct usb_gadget_driver > > *driver) > > > mutex_lock(&udc_lock); > > list_for_each_entry(udc, &udc_list, list) { > > + udc_count++; > > + > > /* For now we take the first one */ > > if (!udc->driver) > > goto found; > > } > > > - printf("couldn't find an available UDC\n"); > > + if (!udc_count) > > + printf("No UDC available in the system\n"); > > + else > > + /* When this happens, users should 'unbind <class> <index>' > > + * using the output of 'dm tree' and looking at the line right > > + * after the USB peripheral/device controller. > > + */ > > + printf("All UDC in use (%d available), use the unbind > > command\n", > > 'UDC' should be plural, e.g. > > %s/All UDC in use (%d available)/All %d UDCs bound/ Does not work well with one: "All 1 UDCs bound" does not look great. I would prefer keeping the original sentence, s/UDC/UDCs/: "All UDCs in use (%d available)". Thanks, Miquèl
