linux-kernel - Re: [PATCH v10 1/4] gadget: Introduce the usb charger framework

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Date:	Fri, 8 Apr 2016 19:51:12 +0800
From:	Baolin Wang <baolin.wang@...aro.org>
To:	Jun Li <jun.li@....com>
Cc:	"balbi@...nel.org" <balbi@...nel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"sre@...nel.org" <sre@...nel.org>,
	"dbaryshkov@...il.com" <dbaryshkov@...il.com>,
	"dwmw2@...radead.org" <dwmw2@...radead.org>,
	"peter.chen@...escale.com" <peter.chen@...escale.com>,
	"stern@...land.harvard.edu" <stern@...land.harvard.edu>,
	"r.baldyga@...sung.com" <r.baldyga@...sung.com>,
	"yoshihiro.shimoda.uh@...esas.com" <yoshihiro.shimoda.uh@...esas.com>,
	"lee.jones@...aro.org" <lee.jones@...aro.org>,
	"broonie@...nel.org" <broonie@...nel.org>,
	"ckeepax@...nsource.wolfsonmicro.com" 
	<ckeepax@...nsource.wolfsonmicro.com>,
	"patches@...nsource.wolfsonmicro.com" 
	<patches@...nsource.wolfsonmicro.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"device-mainlining@...ts.linuxfoundation.org" 
	<device-mainlining@...ts.linuxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v10 1/4] gadget: Introduce the usb charger framework

On 8 April 2016 at 19:27, Jun Li <jun.li@....com> wrote:
>
>
>> -----Original Message-----
>> From: Baolin Wang [mailto:baolin.wang@...aro.org]
>> Sent: Friday, April 08, 2016 7:00 PM
>> To: Jun Li <jun.li@....com>
>> Cc: balbi@...nel.org; gregkh@...uxfoundation.org; sre@...nel.org;
>> dbaryshkov@...il.com; dwmw2@...radead.org; peter.chen@...escale.com;
>> stern@...land.harvard.edu; r.baldyga@...sung.com;
>> yoshihiro.shimoda.uh@...esas.com; lee.jones@...aro.org; broonie@...nel.org;
>> ckeepax@...nsource.wolfsonmicro.com; patches@...nsource.wolfsonmicro.com;
>> linux-pm@...r.kernel.org; linux-usb@...r.kernel.org; device-
>> mainlining@...ts.linuxfoundation.org; linux-kernel@...r.kernel.org
>> Subject: Re: [PATCH v10 1/4] gadget: Introduce the usb charger framework
>>
>> Hi Jun,
>>
>> >> >> +/*
>> >> >> + * usb_charger_detect_type() - detect the charger type manually.
>> >> >> + * @uchger - usb charger device
>> >> >> + *
>> >> >> + * Note: You should ensure you need to detect the charger type
>> >> >> +manually on your
>> >> >> + * platform.
>> >> >> + * You should call it at the right gadget state to avoid
>> >> >> +affecting gadget
>> >> >> + * enumeration.
>> >> >> + */
>> >> >> +int usb_charger_detect_type(struct usb_charger *uchger) {
>> >> >> +     enum usb_charger_type type;
>> >> >> +
>> >> >> +     if (WARN(!uchger->charger_detect,
>> >> >> +              "charger detection method should not be NULL"))
>> >> >> +             return -EINVAL;
>> >> >> +
>> >> >> +     type = uchger->charger_detect(uchger);
>> >> >> +
>> >> >> +     mutex_lock(&uchger->lock);
>> >> >> +     uchger->type = type;
>> >> >> +     mutex_unlock(&uchger->lock);
>> >> >> +
>> >> >> +     return 0;
>> >> >> +}
>> >> >> +EXPORT_SYMBOL_GPL(usb_charger_detect_type);
>> >> >
>> >> > I still recommend have a central place to call
>> >> > usb_charger_detect_type() to cover real charger detection instead
>> >> > of leaving this question open to diff users. This can be done after
>> >> > vbus-on is detected and before do gadget connect. I don't think
>> >> > this
>> >> will make your framework complicated.
>> >>
>> >> This API is used for detecting the charger type manually (software
>> >> charger detection), so if user's udc driver is needed to do this,
>> >> then they can issue it at their right place to make it more flexible.
>> >> But let us see other people's suggestion. Thanks.
>> >
>> > Ok, actually this API can be used for what ever charger detection
>> > type, user can implement any method(manual detection, directly read
>> > result from some HW...what ever) in uchger->charger_detect(), target
>> > is
>>
>> But reading result from some HW dose not means *detect*, actually is *get*.
>> We can not mix them together with the different semantics.
>
> It doesn’t matter here, you already define the _get_ API for just read
> the charger type from the saved value(uchger->type), so we can think
> the API to make uchger->type from UNKNOW to ONE KNOWN type is *detect*,
> because we don't need 2 separate API one for *get* type from HW and another
> one for *detect* from HW, only one API involve HW access is enough.

But another issue is some users may need to get the charger type from
power supply by "power_supply_get_property()" function, we need to
integrate with the power supply things in the usb charger framework,
not user to implement that.

>
> - Detect: (write to and) read from HW to get the charger type,
>   save to uchger->type;
> - Get: read the charger type from uchger->type.
>
>>
>> > to have the charger type and set uchger->type, then you no need to add
>> > the comments/description to limit it usage. Also I do see there is
>> possible central place to do this.
>> >
>>
>> --
>> Baolin.wang
>> Best Regards



-- 
Baolin.wang
Best Regards