linux-kernel - Re: [PATCH 3/6] dt-bindings: HID: i2c-hid: elan: add 'no-reset-on-power-off' property

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Date: Fri, 3 May 2024 11:25:04 +0200
From: Johan Hovold <johan@...nel.org>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Johan Hovold <johan+linaro@...nel.org>, Jiri Kosina <jikos@...nel.org>,
	Benjamin Tissoires <benjamin.tissoires@...hat.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Douglas Anderson <dianders@...omium.org>,
	linux-input@...r.kernel.org, devicetree@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] dt-bindings: HID: i2c-hid: elan: add
 'no-reset-on-power-off' property

On Fri, May 03, 2024 at 11:11:16AM +0200, Krzysztof Kozlowski wrote:
> On 02/05/2024 11:56, Johan Hovold wrote:
> > On Thu, Apr 25, 2024 at 11:39:24AM +0200, Krzysztof Kozlowski wrote:

> >> It seems it is common problem. LEDs have property
> >> "retain-state-shutdown", to indicate that during system shutdown we
> >> should not touch them (like power off). Would some variant be applicable
> >> here? First, do we talk here about power off like system shutdown or
> >> runtime PM, thus suspend?
> > 
> > A name like 'retain-state-shutdown' would also be too specific as what
> > I'm describing here is that the reset line should be (or can be) left
> > deasserted whenever the OS wants to power off the device.
> 
> I don't think it is more specific than yours. It is actually more
> generic. First, shutdown=poweroff, so that part is the same.

My point is that 'shutdown' is a specific OS concept (i.e. turning the
whole system off), while powering off a *device* can be done for a
number of reasons including closing a character device, suspend and
system-wide shutdown.

The policy decision of when to power off a device is left up to kernel
(e.g. if a device needs to be kept on as it is currently configured as a
wakeup device).

Johan