linux-kernel - Re: Re: [PATCH v4 1/3] dt-bindings: HID: i2c-hid: Document reset-related properties

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Date: Thu, 1 Feb 2024 16:08:05 -0600
From: Bjorn Andersson <andersson@...nel.org>
To: Johan Hovold <johan@...nel.org>
Cc: Bjorn Andersson <quic_bjorande@...cinc.com>, 
	Dmitry Torokhov <dmitry.torokhov@...il.com>, Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Benjamin Tissoires <benjamin.tissoires@...hat.com>, Jiri Kosina <jikos@...nel.org>, 
	Konrad Dybcio <konrad.dybcio@...aro.org>, Johan Hovold <johan+linaro@...nel.org>, 
	linux-arm-msm@...r.kernel.org, linux-input@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Konrad Dybcio <konrad.dybcio@...ainline.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>, Rob Herring <robh@...nel.org>
Subject: Re: Re: [PATCH v4 1/3] dt-bindings: HID: i2c-hid: Document
 reset-related properties

On Thu, Feb 01, 2024 at 11:05:47AM +0100, Johan Hovold wrote:
> On Wed, Jan 31, 2024 at 07:07:26PM -0800, Bjorn Andersson wrote:
> > Some I2C HID devices has a reset pin and requires that some specified
> > time elapses after this reset pin is deasserted, before communication
> > with the device is attempted.
> > 
> > The Linux implementation is looking for these in the "reset-gpios" and
> > "post-reset-deassert-delay-ms" properties already, so use these property
> > names.
> > 
> > Reviewed-by: Johan Hovold <johan+linaro@...nel.org>
> > Acked-by: Rob Herring <robh@...nel.org>
> > Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>
> > ---
> >  Documentation/devicetree/bindings/input/hid-over-i2c.yaml | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/input/hid-over-i2c.yaml b/Documentation/devicetree/bindings/input/hid-over-i2c.yaml
> > index 138caad96a29..f07ff4cb3d26 100644
> > --- a/Documentation/devicetree/bindings/input/hid-over-i2c.yaml
> > +++ b/Documentation/devicetree/bindings/input/hid-over-i2c.yaml
> > @@ -50,6 +50,12 @@ properties:
> >      description: Time required by the device after enabling its regulators
> >        or powering it on, before it is ready for communication.
> >  
> > +  post-reset-deassert-delay-ms:
> > +    description: Time required by the device after reset has been deasserted,
> > +      before it is ready for communication.
> 
> I know that Rob reluctantly acked this, but re-reading the commit
> message for the commit that added support for the reset gpio to the
> driver, and added a comment about this not having been added to the
> devicetree binding, it becomes obvious that the latter was done on
> purpose and that we probably should not be adding the
> 'post-reset-deassert-delay-ms' property after all:
> 
> 	For now the new "post-reset-deassert-delay-ms" property is only
> 	used on x86/ACPI (non devicetree) devs. IOW it is not used in
> 	actual devicetree files and the same goes for the reset GPIO.
> 	The devicetree-bindings maintainers have requested properties
> 	like these to not be added to the devicetree-bindings, so the
> 	new property + GPIO are deliberately not added to the existing
> 	devicetree-bindings.
> 
> 	2be404486c05 ("HID: i2c-hid-of: Add reset GPIO support to i2c-hid-of")
> 
> So perhaps we should just do this properly and add a new compatible
> property for X13s touchscreen which can be used to determine these
> delays (e.g. for cases where some default values are insufficient).
> 

So we should add a new binding, with a device-specific compatible and
add a reset-gpios only for that (and not the generic hid-over-i2c
binding), and then in the i2c-hid driver encode the two delays?

I can try to rewrite these patches, if you can provide me with a
compatible.

Regards,
Bjorn