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

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Date:	Wed, 29 Jun 2016 16:38:42 +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

On 29 June 2016 at 16:34, Felipe Balbi <balbi@...nel.org> wrote:
>
> Hi,
>
> 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.
>
> if we have that requirement, that's totally fine. Just rename
> __usb_charger_set_cur_limit() back to
> _usb_charger_set_cur_limit_by_type() and expose both. But
> set_cur_limit_by_type can assume its arguments are valid at all times.

Make sense. I'll fix this issue in v14 version. Thanks.

-- 
Baolin.wang
Best Regards