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

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Date:	Wed, 06 Apr 2016 15:21:41 +0300
From:	Felipe Balbi <balbi@...nel.org>
To:	Jun Li <jun.li@....com>, Baolin Wang <baolin.wang@...aro.org>,
	Peter Chen <hzpeterchen@...il.com>
Cc:	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>,
	"r.baldyga\@samsung.com" <r.baldyga@...sung.com>,
	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,

Jun Li <jun.li@....com> writes:
>> -----Original Message-----
>> From: linux-usb-owner@...r.kernel.org [mailto:linux-usb-
>> owner@...r.kernel.org] On Behalf Of Baolin Wang
>> Sent: Wednesday, April 06, 2016 6:47 PM
>> To: Peter Chen <hzpeterchen@...il.com>
>> Cc: Felipe Balbi <balbi@...nel.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>;
>> r.baldyga@...sung.com; 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@...nsource.wolfsonmicro.com;
>> Linux PM list <linux-pm@...r.kernel.org>; USB <linux-usb@...r.kernel.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
>> 
>> On 6 April 2016 at 15:19, Peter Chen <hzpeterchen@...il.com> wrote:
>> > On Fri, Apr 01, 2016 at 03:21:50PM +0800, Baolin Wang wrote:
>> >>
>> >> @@ -563,6 +564,8 @@ struct usb_gadget_ops {
>> >>       struct usb_ep *(*match_ep)(struct usb_gadget *,
>> >>                       struct usb_endpoint_descriptor *,
>> >>                       struct usb_ss_ep_comp_descriptor *);
>> >> +     /* get the charger type */
>> >> +     enum usb_charger_type (*get_charger_type)(struct usb_gadget *);
>> >>  };
>> >
>> > Since we already have get_charger_type callback at usb_charger
>> > structure, why we still need this API at usb_gadget_ops?
>> 
>> In case some users want to get charger type at gadget level.
>> 
> Why gadget needs to know charger type? I also don't catch the intent of

because some gadgets need to call usb_gadget_vbus_draw(), although for
that they need power in mA rather.

> This api, as my understanding, gadget only need report gadget state changes.
> All information required for usb charger is charger type and gadget state.

you're making an assumption about how the HW is laid out which might not
be true.

-- 
balbi

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