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

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Message-ID: <20200108175834.GC2546185@kroah.com>
Date:   Wed, 8 Jan 2020 18:58:34 +0100
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-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: common: usb-conn-gpio: Register charger

On Wed, Jan 08, 2020 at 02:26:10PM -0300, Paul Cercueil wrote:
> Hi Greg,
> 
> 
> Le mer., janv. 8, 2020 at 17:53, Greg Kroah-Hartman
> <gregkh@...uxfoundation.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.
> 
> 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.

Ok, this is all good info that should go into the changelog text for
when you resend this.

> > 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? Is gpio-b-connector not always used for OTG
> connectors?

I do not know, I thought OTG was dead :)

thanks,

greg k-h