Hi, On Sat, May 03, 2014 at 12:05:41AM -0400, Zhuang Jin Can wrote: > On Thu, May 01, 2014 at 10:13:28AM -0500, Felipe Balbi wrote: > > On Thu, May 01, 2014 at 04:44:52PM -0400, Zhuang Jin Can wrote: > > > On Wed, Apr 30, 2014 at 02:58:29PM -0500, Felipe Balbi wrote: > > > > On Thu, May 01, 2014 at 02:36:08AM -0400, Zhuang Jin Can wrote: > > > > > At least we should giveback the current request to the > > > > > gadget. Otherwise, the gadget will be stuck without knowing > > > > > anything. > > > > > > > > > > It was oberved that the failure can happen if the request is > > > > > queued when the run/stop bit of controller is not set. > > > > > > > > why is your gadget queueing any requests before calling ->udc_start() ? > > > > > > > > A better question, what modification have you done to udc-core.c which > > > > broke this ? udc-core *always* calls ->udc_start() by the time you load > > > > a gadget driver so this case will *never* happen. Whatever modification > > > > you did, broke this assumption and I will *not* accept this patch > > > > because the bug is elsewhere and *not* in mainline kernel. > > > > > > > It's found in Android using kernel 3.10.20. Android has its own > > > usb_composite_driver usb/gadget/android.c (not in mainline), and it > > > > so you found something on an old kernel using an out-of-tree gadget > > driver. > > > > > allows userspace to disconnect the pullup (i.e clear run/stop bit in dwc3) > > > and remove the gadget functions like adb, mtp and then add new functions > > > like rndis, acm. The problem is when you disconnect the pullup, a gadget > > > maybe in the middle of queuing a request, and result in the "start > > > transfer cmd failure". I think this is also a common issue for other > > > > Android gadget needs to learn how to cope with that. > > > Agree. > > > > usb_composite_drivers too. Normally, if one of the gadget deactivate its > > > own function, the pullup will be disconnected, other gadgets won't get > > > notified until their requests are failed. So it makes dwc3 more robust > > > to deal with these situations. > > > > Right, but Android gadget can run on top of several other UDCs and you > > want to have a single one of them cope with android's bug ? > > > > You'd be better off getting google to accept a bugfix to the android > > gadget, since that's where the problem lies. > > > I agree. I'll try to push the fix to google. alright, thanks > It's really hard to fix the race condition (for me), as any gadget or > /sys/class/udc/soft_connect can just disconnect the pullup anytime they > want. The only thing I can do is giving back the request to the > gadget if the condition happens. even in that case, gadget driver's ->disconnect() will be called and that should be enough to tell the gadget driver 'hey, don't queue anything right now because you're not talking to any host'. cheers -- balbi
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