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SubjectRe: [PATCH] usb: common: usb-conn-gpio: Register charger
Hi Chunfeng,

Le jeu., janv. 9, 2020 at 10:27, Chunfeng Yun
<chunfeng.yun@mediatek.com> a écrit :
> Hi Paul,
>
> On Wed, 2020-01-08 at 14:26 -0300, Paul Cercueil wrote:
>> Hi Greg,
>>
>>
>> Le mer., janv. 8, 2020 at 17:53, Greg Kroah-Hartman
>> <gregkh@linuxfoundation.org> a écrit :
>> > On Tue, Jan 07, 2020 at 01:29:01AM +0100, Paul Cercueil wrote:
>> >> Register a power supply charger, whose online state depends on
>> >> whether
>> >> the USB role is set to device or not.
>> >
>> > That says _what_ you are doing, but I have no idea _why_ you want
>> to
>> > do
>> > this.
>> >
>> > What is this going to cause to have happen? What new userspace
>> api is
>> > going to result? What will a user do with this?
>>
>> This is useful when the USB role is the only way to know if the
>> device
>> is charging from USB.
> There is no charger IC on your platform?

Correct.

>
>>
>> The API is the standard power supply charger API, you get a
>> /sys/class/power_supply/xxx/online node which tells you the state of
>> the charger.
>>
>> The sole purpose of this is to give userspace applications a way to
>> know whether or not the charger is plugged.
>>
>> > Is this going to always show up, no matter if the role is not even
>> > relevant for a power supply?
>>
>> I guess it'd always show up, yes. In which case would the role not
>> be
>> relevant for a power supply?
> Do you also need it if the platform don't have battery?

I guess not. Would you prefer it to be disabled by default? If so, what
would be the way to have it enabled? A flag in devicetree?

>
>> Is gpio-b-connector not always used for
>> OTG connectors?
> It also supports device only mode, usually uses vBus pin to
> enable/disable controller

Yes, that would work too. The problem would be a host-only
gpio-b-connector.

-Paul


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