Re: [PATCH v10 06/14] usb: gadget.h: Add OTG to gadget interface

From	Felipe Balbi <balbi@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v10 06/14] usb: gadget.h: Add OTG to gadget interface
Date	2016-06-20 11:30 +0200
Message-ID	<rM3GO-6p3-23@gated-at.bofh.it> (permalink)
References	(1 earlier) <rIumd-4YI-1@gated-at.bofh.it> <rM1OF-5eM-9@gated-at.bofh.it> <rM1OF-5eM-25@gated-at.bofh.it> <rM2B3-5Mx-15@gated-at.bofh.it> <rM2Up-5T4-11@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Hi,

Roger Quadros <rogerq@ti.com> writes:
>>>> Roger Quadros <rogerq@ti.com> writes:
>>>>> The OTG core will use struct otg_gadget_ops to
>>>>> start/stop the gadget controller.
>>>>>
>>>>> The main purpose of this interface is to avoid directly
>>>>> calling usb_gadget_start/stop() from the OTG core as they
>>>>> wouldn't be defined in the built-in symbol table if
>>>>> CONFIG_USB_GADGET is m.
>>>>>
>>>>> Signed-off-by: Roger Quadros <rogerq@ti.com>
>>>>> ---
>>>>>  include/linux/usb/gadget.h | 16 ++++++++++++++++
>>>>>  1 file changed, 16 insertions(+)
>>>>>
>>>>> diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
>>>>> index 2dd9e6b..f4fc0aa 100644
>>>>> --- a/include/linux/usb/gadget.h
>>>>> +++ b/include/linux/usb/gadget.h
>>>>> @@ -639,6 +639,22 @@ struct usb_gadget_driver {
>>>>>  };
>>>>>  
>>>>>  
>>>>> +/*-------------------------------------------------------------------------*/
>>>>> +
>>>>> +/**
>>>>> + * struct otg_gadget_ops - Interface between OTG core and gadget
>>>>> + *
>>>>> + * Provided by the gadget core to allow the OTG core to start/stop the gadget
>>>>> + *
>>>>> + * @start: function to start the gadget
>>>>> + * @stop: function to stop the gadget
>>>>> + * @connect_control: function to connect/disconnect from the bus
>>>>> + */
>>>>> +struct otg_gadget_ops {
>>>>> +	int (*start)(struct usb_gadget *gadget);
>>>>> +	int (*stop)(struct usb_gadget *gadget);
>>>>> +	int (*connect_control)(struct usb_gadget *gadget, bool connect);
>>>>> +};
>>>>
>>>> you shouldn't need these at all. They are already part of the gadget
>>>> framework as ->udc_start(), ->udc_stop() and ->pullup()
>>>>
>>>
>>> This is to avoid the undefined symbol errors during build when OTG has is
>>> built-in because USB (host) is built-in but GADGET is still a module.
>> 
>> change your Kconfig dependencies. OTG layer shouldn't be built-in unless
>> both Gadget and Host are built-in.
>> 
>
> That is only one side of the story.
> What happens if OTG is (m), Host is (m) but Gadget is (built in).
>
> Gadget build will fail because of undefined symbol errors for all of
> the OTG APIs.

So you created a circular dependency, right? That's not good either. I
suggest you clean that up because this is bound to create randconfig
build problems in the long run.

-- 
balbi

Thread

Re: [PATCH v10 06/14] usb: gadget.h: Add OTG to gadget interface Felipe Balbi <balbi@kernel.org> - 2016-06-20 09:30 +0200
  Re: [PATCH v10 06/14] usb: gadget.h: Add OTG to gadget interface Roger Quadros <rogerq@ti.com> - 2016-06-20 09:30 +0200
    Re: [PATCH v10 06/14] usb: gadget.h: Add OTG to gadget interface Felipe Balbi <balbi@kernel.org> - 2016-06-20 10:20 +0200
      Re: [PATCH v10 06/14] usb: gadget.h: Add OTG to gadget interface Roger Quadros <rogerq@ti.com> - 2016-06-20 10:40 +0200
        Re: [PATCH v10 06/14] usb: gadget.h: Add OTG to gadget interface Felipe Balbi <balbi@kernel.org> - 2016-06-20 11:30 +0200
          Re: [PATCH v10 06/14] usb: gadget.h: Add OTG to gadget interface Roger Quadros <rogerq@ti.com> - 2016-06-20 12:00 +0200

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