linux-kernel - Re: [PATCH v4 3/3] Documentation: power: rt9471: Document exported sysfs entries

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Message-ID: <20220912112955.cpbzov6h7am4m37b@mercury.elektranox.org>
Date:   Mon, 12 Sep 2022 13:29:55 +0200
From:   Sebastian Reichel <sebastian.reichel@...labora.com>
To:     cy_huang <u0084500@...il.com>
Cc:     robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        mazziesaccount@...il.com, alina_yu@...htek.com,
        cy_huang@...htek.com, alinayu829@...il.com,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 3/3] Documentation: power: rt9471: Document exported
 sysfs entries

Hi,

On Mon, Sep 12, 2022 at 01:12:01PM +0200, Sebastian Reichel wrote:
> On Mon, Aug 29, 2022 at 11:06:31AM +0800, cy_huang wrote:
> > From: ChiYuan Huang <cy_huang@...htek.com>
> > 
> > Document the settings exported by rt9471 charger driver through sysfs entries:
> > - sysoff_enable
> > - charge_term_enable
> > - port_detect_enable
> > 
> > Signed-off-by: ChiYuan Huang <cy_huang@...htek.com>
> > ---
> >  Documentation/ABI/testing/sysfs-class-power | 44 +++++++++++++++++++++++++++++
> >  1 file changed, 44 insertions(+)

I forgot to mention: custom driver properties are described in their
own files, see Documentation/ABI/testing/sysfs-class-power-*. But
are to be avoided if possible. So first of all I want to make sure
you actually need any of these.

-- Sebastian

> > 
> > diff --git a/Documentation/ABI/testing/sysfs-class-power b/Documentation/ABI/testing/sysfs-class-power
> > index a9ce63c..1f8afe5 100644
> > --- a/Documentation/ABI/testing/sysfs-class-power
> > +++ b/Documentation/ABI/testing/sysfs-class-power
> > @@ -768,3 +768,47 @@ Description:
> >  
> >  		Access: Read
> >  		Valid values: 1-31
> > +
> > +What:		/sys/class/power_supply/rt9471-*/sysoff_enable
> > +Date:		Sep 2022
> > +KernelVersion:	6.1
> > +Contact:	ChiYuan Huang <cy_huang@...htek.com>
> > +Description:
> > +		This entry allows enabling the sysoff mode of rt9471 charger devices.
> > +		If enabled and the input is removed, the internal battery FET is turned
> > +		off to reduce the leakage from the BAT pin. See device datasheet for details.
> > +
> > +		Access: Read, Write
> > +		Valid values:
> > +		- 1: enabled
> > +		- 0: disabled
> 
> This is not a very good description of what the control does. When
> do you expect users to control this?
> 
> > +What:		/sys/class/power_supply/rt9471-*/charge_term_enable
> > +Date:		Sep 2022
> > +KernelVersion:	6.1
> > +Contact:	ChiYuan Huang <cy_huang@...htek.com>
> > +Description:
> > +		This entry allows enabling the charge termination function of rt9471 charger
> > +		devices. If enabled, the battery charging current, and the battery voltage
> > +		reachs charge termination condition, the internal battery FET will be turned off
> > +		to optimize the battery life. See device datasheet for details.
> > +
> > +		Access: Read, Write
> > +		Valid values:
> > +		- 1: enabled
> > +		- 0: disabled
> 
> Just write 0 to .../charge_term_current to disable it.
> No need for a custom property.
> 
> > +What:		/sys/class/power_supply/rt9471-*/port_detect_enable
> > +Date:		Sep 2022
> > +KernelVersion:	6.1
> > +Contact:	ChiYuan Huang <cy_huang@...htek.com>
> > +Description:
> > +		This entry allows enabling the USB BC12 port detect function of rt9471 charger
> > +		devices. If enabled and VBUS is inserted, device will start to do the BC12
> > +		port detect and report the usb port type when port detect is done. See
> > +		datasheet for details.
> > +
> > +		Access: Read, Write
> > +		Valid values:
> > +		- 1: enabled
> > +		- 0: disabled
> 
> Why would one want to disable this?
> Can't the driver just enable it unconditionally?
> 
> -- Sebastian



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