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

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Message-ID: <20200721114101.GA1761915@kroah.com>
Date:   Tue, 21 Jul 2020 13:41:01 +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 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?

thanks,

greg k-h