linux-kernel - Re: [PATCH v9 2/4] gadget: Support for the usb charger framework

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Date:	Thu, 07 Apr 2016 07:58:46 +0300
From:	Felipe Balbi <balbi@...nel.org>
To:	Peter Chen <hzpeterchen@...il.com>
Cc:	Jun Li <jun.li@....com>, Baolin Wang <baolin.wang@...aro.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	Sebastian Reichel <sre@...nel.org>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Peter Chen <peter.chen@...escale.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
	Lee Jones <lee.jones@...aro.org>,
	Mark Brown <broonie@...nel.org>,
	Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>,
	"patches\@opensource.wolfsonmicro.com" 
	<patches@...nsource.wolfsonmicro.com>,
	Linux PM list <linux-pm@...r.kernel.org>,
	USB <linux-usb@...r.kernel.org>,
	"device-mainlining\@lists.linuxfoundation.org" 
	<device-mainlining@...ts.linuxfoundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 2/4] gadget: Support for the usb charger framework


Hi,

Peter Chen <hzpeterchen@...il.com> writes:
>> >> > In below change of usb_gadget_vbus_draw(), already can get charger
>> >> > type via usb_charger_get_type().
>> >> >
>> >> > static inline int usb_gadget_vbus_draw(struct usb_gadget *gadget,
>> >> > unsigned mA)  {
>> >> > +       enum usb_charger_type type;
>> >> > +
>> >> > +       if (gadget->charger) {
>> >> > +               type = usb_charger_get_type(gadget->charger);
>> >> > +               usb_charger_set_cur_limit_by_type(gadget->charger, type,
>> >> mA);
>> >> > +       }
>> >> > +
>> >> >         if (!gadget->ops->vbus_draw)
>> >> >                 return -EOPNOTSUPP;
>> >> >         return gadget->ops->vbus_draw(gadget, mA);
>> >> >
>> >> > Could you detail in what situation gadget->ops-> get_charger_type() is
>> >> used?
>> >> 
>> >> isn't it right there in the code ? Isn't usb_gadget_vbus_draw() calling
>> >> it ? What did I miss here ?
>> >
>> > Well, that's true, so my real meaning is why gadget need get charger type
>> > via another new api gadget->ops->get_charger_type().
>> 
>> because of semantics. usb_gadget_vbus_draw() is *only* supposed to
>> connect a load across vbus and gnd so some battery can be charged. Also,
>> we need to abstract away this ->get_charger_type() operation because it
>> might be different for each UDC.
>
> In this patch set, there are two ->get_charger_type in below two
> structures, as my understanding, get_charger_type at struct usb_charger
> can be implemented at UDC drivers; But I don't see necessary we
> need to implement get_charger_type for usb_gadget_ops at UDC drivers
> again. What do you think?

I had missed that completely, nice catch. I agree with you, there should
be one place where this is implemented and struct usb_charger sounds
like it is that place.

-- 
balbi

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