linux-kernel - Re: [PATCH v12 2/4] gadget: Support for the usb charger framework

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Date:	Wed, 29 Jun 2016 16:31:12 +0800
From:	Baolin Wang <baolin.wang@...aro.org>
To:	Felipe Balbi <balbi@...nel.org>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	Sebastian Reichel <sre@...nel.org>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>, robh@...nel.org,
	Jun Li <jun.li@....com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Ruslan Bilovol <ruslan.bilovol@...il.com>,
	Peter Chen <peter.chen@...escale.com>,
	Alan Stern <stern@...land.harvard.edu>, r.baldyga@...sung.com,
	grygorii.strashko@...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 v12 2/4] gadget: Support for the usb charger framework

Hi Felipe,

On 29 June 2016 at 16:20, Felipe Balbi <balbi@...nel.org> wrote:
>
> Hi,
>
> Baolin Wang <baolin.wang@...aro.org> writes:
>>> Baolin Wang <baolin.wang@...aro.org> writes:
>>>> For supporting the usb charger, it adds the usb_charger_init() and
>>>> usb_charger_exit() functions for usb charger initialization and exit.
>>>>
>>>> It will report to the usb charger when the gadget state is changed,
>>>> then the usb charger can do the power things.
>>>>
>>>> Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
>>>> Reviewed-by: Li Jun <jun.li@....com>
>>>> Tested-by: Li Jun <jun.li@....com>
>>>
>>> Before anything, I must say that I really liked this patch. It's
>>> minimaly invasive to udc core and does all the necessary changes. If it
>>> wasn't for the extra charger class, this would've been perfect.
>>>
>>> Can't you just tie a charger to a UDC and avoid the charger class
>>> completely?
>>>
>>>>  static inline int usb_gadget_vbus_draw(struct usb_gadget *gadget, unsigned mA)
>>>>  {
>>>> +     if (gadget->charger)
>>>
>>> I guess you could do this check inside
>>> usb_gadget_set_cur_limit_by_type() itself.
>>
>> We will access the 'gadget->charger->type' member when issuing
>> usb_gadget_set_cur_limit_by_type(), so I think I should leave the
>> check here in next new version.
>
> Here's what I mean:
>
> int usb_charger_set_cur_limit(struct usb_gadget *gadget, unsigned int mA)
> {
>         struct usb_charger *charger;
>         enum usb_charger_type type;
>
>         if (!gadget->charger)
>                 return 0;
>
>         charger = gadget->charger;
>         type = charger->type;
>
>         return __usb_charger_set_cur_limit(charger, type, mA);
> }

But that means we need to export  both 'usb_charger_set_cur_limit()'
function and '__usb_charger_set_cur_limit()' function in charger.c
file. Cause some user may want to set the current limitation by one
charger type parameter (may be not from charger->type), like by
issuing '__usb_charger_set_cur_limit(charger, SDP_TYPE, mA)'. How do
you think about this situation? Thanks.

>
> static inline int usb_gadget_vbus_draw(struct usb_gadget *gadget, unsigned mA)
> {
>         usb_charger_set_cur_limit(gadget,  mA);
>
>         if (!gadget->ops->vbus_draw)
>                 return -EOPNOTSUPP;
>         return gadget->ops->vbus_draw(gadget, mA);
> }
>
> --
> balbi



-- 
Baolin.wang
Best Regards