linux-kernel - Re: [RESEND PATCH] usb: common: usb-conn-gpio: Register optional charger

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Date:   Sun, 26 Jul 2020 10:39:22 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     Chunfeng Yun <chunfeng.yun@...iatek.com>, od@...c.me,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH] usb: common: usb-conn-gpio: Register optional
 charger

On Sat, Jul 25, 2020 at 07:51:14PM +0200, Paul Cercueil wrote:
> Hi Greg,
> 
> Le mar. 21 juil. 2020 à 13:41, Greg Kroah-Hartman
> <gregkh@...uxfoundation.org> a écrit :
> > On Mon, Jun 22, 2020 at 12:48:07AM +0200, Paul Cercueil wrote:
> > >  Register a power supply charger, if the Kconfig option
> > >  USB_CONN_GPIO_CHARGER is set, whose online state depends on whether
> > >  the USB role is set to device or not.
> > > 
> > >  This is useful when the USB role is the only way to know if the
> > > device
> > >  is charging from USB. 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.
> > > 
> > >  Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> > >  ---
> > >   drivers/usb/common/Kconfig         | 11 +++++++
> > >   drivers/usb/common/usb-conn-gpio.c | 47
> > > ++++++++++++++++++++++++++++++
> > >   2 files changed, 58 insertions(+)
> > > 
> > >  diff --git a/drivers/usb/common/Kconfig b/drivers/usb/common/Kconfig
> > >  index d611477aae41..5405ae96c68f 100644
> > >  --- a/drivers/usb/common/Kconfig
> > >  +++ b/drivers/usb/common/Kconfig
> > >  @@ -49,3 +49,14 @@ config USB_CONN_GPIO
> > > 
> > >   	  To compile the driver as a module, choose M here: the module
> > > will
> > >   	  be called usb-conn-gpio.ko
> > >  +
> > >  +if USB_CONN_GPIO
> > >  +
> > >  +config USB_CONN_GPIO_CHARGER
> > >  +	bool "USB charger support"
> > >  +	select POWER_SUPPLY
> > >  +	help
> > >  +	  Register a charger with the power supply subsystem. This will
> > > allow
> > >  +	  userspace to know whether or not the device is charging from
> > > USB.
> > 
> > Why make this an option at all?  Why wouldn't we always want this here?
> > 
> > As this is a charger, exporting that information to userspace should
> > probably always happen, right?
> 
> I wanted to avoid the hardcoded dependency on CONFIG_POWER_SUPPLY.
> 
> I can very well make that non-optional.

As the whole reason for this driver is to be a power supply, make it
depend on the power supply core please.

thanks,

greg k-h