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

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Date:   Sat, 25 Jul 2020 19:51:14 +0200
From:   Paul Cercueil <paul@...pouillou.net>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
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

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.

Cheers,
-Paul

> thanks,
> 
> greg k-h