On Sun, Jan 4, 2015 at 1:44 AM, Felipe Balbi <balbi@xxxxxx> wrote: > Hi, > > On Sat, Jan 03, 2015 at 10:53:20PM +1100, Daniel Tang wrote: >> Hi, >> >> I’ve run into a problem which I suspect is to with how >> usb_gadget_probe_driver is implemented in >> drivers/usb/gadget/udc/udc-core.c >> >> I have an embedded system that uses the Chipidea OTG controller. >> Unfortunately, when it boots up, the driver is loaded but there’s no >> USB gadget that gets attached to it. I’m building the USB gadget >> support into the kernel. > > statically linking gadget drivers has an old known problem which nobody > has been able to provide a good solution. If you wanna tackle it, we'll > review patches, for sure. > I have un-finished patch set for it, Daniel, if you have time, you can go on it (g_mass_storage has some issues for it) An easy way to workaround this issue is register your build-in gadget driver with late_initcall. >> Here’s a snippet of the boot log: >> >> Console: switching to colour frame buffer device 40x30 >> Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled >> Serial: AMBA driver >> brd: module loaded >> ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver >> zevio_usb b0000000.usb: ci_hdrc_zevio_probe >> zevio_usb b0000000.usb: ci_hdrc_add_device failed! >> platform b0000000.usb: Driver zevio_usb requests probe deferral >> userial_init: registered 4 ttyGS* devices >> couldn't find an available UDC >> mousedev: PS/2 mouse device common for all mice >> usbcore: registered new interface driver usbhid >> usbhid: USB HID core driver >> zevio_usb b0000000.usb: ci_hdrc_zevio_probe >> ci_hdrc ci_hdrc.0: ChipIdea HDRC found, lpm: 0; cap: c4882100 op: c4882140 >> ci_hdrc ci_hdrc.0: It is OTG capable controller >> USB VBUS output: disabling >> RAMDISK: gzip image found at block 0 >> >> It seems that because the Chipidea driver requests a probe deferral >> (presumably to wait for some device it depends on to get probed), it >> doesn’t get loaded before usb_gadget_probe_driver is called. Hence, >> usb_gadget_probe_driver doesn’t find anything it can bind to and it >> errors out. By the time the Chipidea driver actually finishes getting >> probed, it’s too late to bind any gadgets to. >> >> Does this sound like a reasonable diagnosis? What can we do about it? > > yeah, that's correct. > > -- > balbi -- BR, Peter Chen -- 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
