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

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Date:	Fri, 8 Apr 2016 11:27:01 +0000
From:	Jun Li <jun.li@....com>
To:	Baolin Wang <baolin.wang@...aro.org>
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



> -----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.

- 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