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

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Date:	Wed, 29 Jun 2016 11:34:21 +0300
From:	Felipe Balbi <balbi@...nel.org>
To:	Baolin Wang <baolin.wang@...aro.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,

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.

-- 
balbi

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