Re: [PATCH] usb: common: usb-conn-gpio: Register charger

[Paul Cercueil]

Hi Chunfeng,

Le jeu., janv. 9, 2020 at 10:27, Chunfeng Yun 
<chunfeng.yun@xxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxx> 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