Messages in this thread | | | Date | Mon, 23 Nov 2015 15:40:31 +0800 | From | Peter Chen <> | Subject | Re: [PATCH v6 4/4] usb: gadget: udc-core: independent registration of gadgets and gadget drivers |
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On Fri, Nov 20, 2015 at 11:27:36AM -0500, Alan Stern wrote: > On Fri, 20 Nov 2015, Marek Szyprowski wrote: > > > From: Ruslan Bilovol <ruslan.bilovol@gmail.com> > > > > Change behavior during registration of gadgets and > > gadget drivers in udc-core. Instead of previous > > approach when for successful probe of usb gadget driver > > at least one usb gadget should be already registered > > use another one where gadget drivers and gadgets > > can be registered in udc-core independently. > > > > Independent registration of gadgets and gadget drivers > > is useful for built-in into kernel gadget and gadget > > driver case - because it's possible that gadget is > > really probed only on late_init stage (due to deferred > > probe) whereas gadget driver's probe is silently failed > > on module_init stage due to no any UDC added. > > > > Also it is useful for modules case - now there is no > > difference what module to insert first: gadget module > > or gadget driver one. > > > > Tested-by: Maxime Ripard <maxime.ripard@free-electrons.com> > > Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com> > > [simplified code as requested by Alan Stern and Felipe Balbi] > > Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> > > ... > > > @@ -475,9 +492,16 @@ void usb_del_gadget_udc(struct usb_gadget *gadget) > > list_del(&udc->list); > > mutex_unlock(&udc_lock); > > > > - if (udc->driver) > > + if (udc->driver) { > > + struct usb_gadget_driver *driver = udc->driver; > > + > > usb_gadget_remove_driver(udc); > > > > + mutex_lock(&udc_lock); > > + list_add(&driver->pending, &gadget_driver_pending_list); > > + mutex_unlock(&udc_lock); > > + } > > It looks like there is a race here with usb_gadget_unregister_driver(). > Would it be okay to hold the udc_lock mutex throughout the whole "if" > statement? >
+1
In fact, only one mutex_lock/mutex_unlock is needed at this function. --
Best Regards, Peter Chen
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