linux-kernel - Re: [PATCH v2 0/3] Introduce usb charger framework to deal with the usb gadget power negotation

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Date:	Mon, 17 Aug 2015 16:20:24 +0800
From:	Li Jun <b47624@...escale.com>
To:	Baolin Wang <baolin.wang@...aro.org>
CC:	Felipe Balbi <balbi@...com>, Mark Brown <broonie@...nel.org>,
	"Linus Walleij" <linus.walleij@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	Peter Chen <peter.chen@...escale.com>, <sojka@...ica.cz>,
	Alan Stern <stern@...land.harvard.edu>,
	<r.baldyga@...sung.com>, <yoshihiro.shimoda.uh@...esas.com>,
	<linux-usb@...r.kernel.org>,
	<device-mainlining@...ts.linuxfoundation.org>, <sre@...nel.org>,
	"Dmitry Eremin-Solenikov" <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>, <sameo@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>,
	<patches@...nsource.wolfsonmicro.com>, <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v2 0/3] Introduce usb charger framework to deal with the
 usb gadget power negotation

On Mon, Aug 17, 2015 at 02:02:08PM +0800, Baolin Wang wrote:
> On 17 August 2015 at 09:15, Li Jun <b47624@...escale.com> wrote:
> > On Fri, Aug 14, 2015 at 07:04:56PM +0800, Baolin Wang wrote:
> >> On 14 August 2015 at 16:55, Li Jun <b47624@...escale.com> wrote:
> >> > Hi Baolin,
> >> >
> >> > On Fri, Aug 14, 2015 at 05:47:43PM +0800, Baolin Wang wrote:
> >> >> Currently the Linux kernel does not provide any standard integration of this
> >> >> feature that integrates the USB subsystem with the system power regulation
> >> >> provided by PMICs meaning that either vendors must add this in their kernels
> >> >> or USB gadget devices based on Linux (such as mobile phones) may not behave
> >> >> as they should.
> >> >>
> >> >> Providing a standard framework for doing this in the kernel.
> >> >>
> >> >
> >> > Why not add power supply class support into this?
> >> >
> >>
> >> Hi Jun,
> >>
> >> We don't need the power supply class support into the usb charger,
> > I suppose usb charger is also a power supply for the system, we can use power
> > supply class framework for notify mechanism and get/set many attributes(maybe
> > also the current limit), I see those usb charger drivers under ./driver/power/
> > are designed with power supply supported.
> >
> 
> I don't think so. The usb charger is rely on the usb gadget, which is
> not a complete power supply device and it combines the usb and the
> power supply. Thus we make it into usb gadget system. Thanks.
> 
Why it cannot be a complete power supply device? I was thinking this
framework can cover it, I have no doubt on putting this framework
into gadget system, but still can't understand why we don't need
power supply class at all for a usb charger, or you think introduce
power supply into usb gadget is not a right direction from code structure
point view?

Li Jun
> > Li Jun
> >> just introduce the notify mechanism for power to set the current limit
> >> when notifying some events from usb charger. Maybe I misunderstand
> >> your meanings, please describe it detailedly. Thanks for your
> >> comments.
> >>
> >> > Li Jun
> >> >
> >>
> >>
> >>
> >> --
> >> Baolin.wang
> >> Best Regards
> 
> 
> 
> -- 
> Baolin.wang
> Best Regards
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