On Fri, Jun 13, 2014 at 10:19:36AM -0400, Alan Stern wrote: > On Fri, 13 Jun 2014, Peter Chen wrote: > > > OK, we can keep our g_xxx gadget driver just support the basic feature. But > > the bug that causes gadget driver load fail due to udc is probed deferral > > should > > be fixed, do you think so, we can't wait until configfs has total been > > ready. > > That problem has always existed. There never has been a time when a > gadget driver could be loaded before the UDC driver was ready. Does it > really need to be fixed now? >
Yes, otherwise, the device which the udc is probed deferral and the gadget driver is build-in will never work. If we skip fixing it, this problem will exist for more than 2 years, it is too long. I have a support request from android team that usb peripheral function never works from 3.10.x kernel at one device, I think it is a common problem, no only I meet it. Below are links which this problem reports: http://marc.info/?l=linux-usb&m=139380872501745&w=2 http://marc.info/?l=linux-usb&m=137706435611447&w=2 > If you do want to fix the problem, there's a much easier way than what > you posted. See below. > Robert Baldyga posts the similar solution, but seems Felipe doesn't agree it. http://www.spinics.net/lists/linux-usb/msg102795.html Then, you and Felipe has a discussion for this problem: http://www.spinics.net/lists/linux-usb/msg106760.html > > Index: usb-3.15/include/linux/usb/gadget.h > =================================================================== > --- usb-3.15.orig/include/linux/usb/gadget.h > +++ usb-3.15/include/linux/usb/gadget.h > @@ -821,6 +821,7 @@ static inline int usb_gadget_disconnect( > * @suspend: Invoked on USB suspend. May be called in_interrupt. > * @resume: Invoked on USB resume. May be called in_interrupt. > * @driver: Driver model state for this driver. > + * @probe_list: List of drivers waiting to be probed. > * > * Devices are disabled till a gadget driver successfully bind()s, which > * means the driver will handle setup() requests needed to enumerate (and > @@ -881,6 +882,7 @@ struct usb_gadget_driver { > > /* FIXME support safe rmmod */ > struct device_driver driver; > + struct list_head probe_list; > }; > > > Index: usb-3.15/drivers/usb/gadget/udc-core.c > =================================================================== > --- usb-3.15.orig/drivers/usb/gadget/udc-core.c > +++ usb-3.15/drivers/usb/gadget/udc-core.c > @@ -47,8 +47,12 @@ struct usb_udc { > > static struct class *udc_class; > static LIST_HEAD(udc_list); > +static LIST_HEAD(pending_drivers); > static DEFINE_MUTEX(udc_lock); > > +static int udc_bind_to_driver(struct usb_udc *udc, > + struct usb_gadget_driver *driver); > + > /* ------------------------------------------------------------------------- > */ > > #ifdef CONFIG_HAS_DMA > @@ -242,6 +246,15 @@ int usb_add_gadget_udc_release(struct de > > usb_gadget_set_state(gadget, USB_STATE_NOTATTACHED); > > + while (!list_empty(&pending_drivers)) { > + struct usb_gadget_driver *driver; > + > + driver = list_first_entry(&pending_drivers, > + struct usb_gadget_driver, probe_list); > + if (udc_bind_to_driver(udc, driver) == 0) > + break; > + } > + > mutex_unlock(&udc_lock); > > return 0; > @@ -338,6 +351,7 @@ static int udc_bind_to_driver(struct usb > > dev_dbg(&udc->dev, "registering UDC driver [%s]\n", > driver->function); > + list_del_init(&driver->probe_list); > > udc->driver = driver; > udc->dev.driver = &driver->driver; > @@ -400,6 +414,7 @@ int usb_gadget_probe_driver(struct usb_g > return -EINVAL; > > mutex_lock(&udc_lock); > + INIT_LIST_HEAD(&driver->probe_list); > list_for_each_entry(udc, &udc_list, list) { > /* For now we take the first one */ > if (!udc->driver) > @@ -407,8 +422,9 @@ int usb_gadget_probe_driver(struct usb_g > } > > pr_debug("couldn't find an available UDC\n"); > + list_add_tail(&driver->probe_list, &pending_drivers); > mutex_unlock(&udc_lock); > - return -ENODEV; > + return 0; > found: > ret = udc_bind_to_driver(udc, driver); > mutex_unlock(&udc_lock); > @@ -425,6 +441,7 @@ int usb_gadget_unregister_driver(struct > return -EINVAL; > > mutex_lock(&udc_lock); > + list_del(&driver->probe_list); > list_for_each_entry(udc, &udc_list, list) > if (udc->driver == driver) { > usb_gadget_remove_driver(udc); > > -- Best Regards, Peter Chen -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
