Re: [PATCH 03/40] dt-bindings: touchscreen: ti,am3359-tsc: New yaml description

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 2 Sep 2021 19:45:36 +0200
Miquel Raynal <miquel.raynal@bootlin.com> wrote:

> Hi Jonathan,
> 
> Jonathan Cameron <jic23@kernel.org> wrote on Mon, 30 Aug 2021 14:36:10
> +0100:
> 
> > On Wed, 25 Aug 2021 17:24:41 +0200
> > Miquel Raynal <miquel.raynal@bootlin.com> wrote:
> >   
> > > This touchscreen controller is already described in a text file:
> > > Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
> > > 
> > > After introducing a proper description of the MFD, this is the second
> > > step. The file cannot be removed yet as it also contains an ADC
> > > description.
> > > 
> > > Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> > > ---
> > >  .../input/touchscreen/ti,am3359-tsc.yaml      | 89 +++++++++++++++++++
> > >  1 file changed, 89 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/input/touchscreen/ti,am3359-tsc.yaml
> > > 
> > > diff --git a/Documentation/devicetree/bindings/input/touchscreen/ti,am3359-tsc.yaml b/Documentation/devicetree/bindings/input/touchscreen/ti,am3359-tsc.yaml
> > > new file mode 100644
> > > index 000000000000..2d4ce6d04f53
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/input/touchscreen/ti,am3359-tsc.yaml
> > > @@ -0,0 +1,89 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/input/touchscreen/ti,am3359-tsc.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: TI AM3359 Touchscreen controller
> > > +
> > > +maintainers:
> > > +  - Miquel Raynal <miquel.raynal@bootlin.com>
> > > +
> > > +properties:
> > > +  compatible:
> > > +    const: ti,am3359-tsc
> > > +
> > > +  ti,wires:
> > > +    description: Wires refer to application modes i.e. 4/5/8 wire touchscreen
> > > +      support on the platform.
> > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > +    enum: [4, 5, 8]
> > > +
> > > +  ti,x-plate-resistance:
> > > +    description: X plate resistance
> > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > +
> > > +  ti,coordinate-readouts:
> > > +    description: The sequencer supports a total of 16 programmable steps. Each
> > > +      step is used to read a single coordinate. A single readout is enough but
> > > +      multiple reads can increase the quality. A value of 5 means, 5 reads for
> > > +      X, 5 for Y and 2 for Z (always). This utilises 12 of the 16 software steps
> > > +      available. The remaining 4 can be used by the ADC.
> > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > +    minimum: 1
> > > +    maximum: 6
> > > +
> > > +  ti,wire-config:
> > > +    description: Different boards could have a different order for connecting
> > > +      wires on touchscreen. We need to provide an 8-bit number where the
> > > +      first four bits represent the analog lines and the next 4 bits represent
> > > +      positive/negative terminal on that input line. Notations to represent the
> > > +      input lines and terminals respectively are as follows, AIN0 = 0, AIN1 = 1
> > > +      and so on untill AIN7 = 7. XP = 0, XN = 1, YP = 2, YN = 3.
> > > +    $ref: /schemas/types.yaml#/definitions/uint32-array
> > > +    minItems: 4
> > > +    maxItems: 8
> > > +
> > > +  ti,charge-delay:
> > > +    description: Length of touch screen charge delay step in terms of ADC clock
> > > +      cycles. Charge delay value should be large in order to avoid false pen-up
> > > +      events. This value effects the overall sampling speed, hence need to be
> > > +      kept as low as possible, while avoiding false pen-up event. Start from a
> > > +      lower value, say 0x400, and increase value until false pen-up events are
> > > +      avoided. The pen-up detection happens immediately after the charge step,
> > > +      so this does in fact function as a hardware knob for adjusting the amount
> > > +      of "settling time".
> > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > +
> > > +required:
> > > +  - compatible
> > > +  - ti,wires    
> > 
> > Are these all required?  Seems like the driver will work fine without some
> > of them and isn't doing appropriate error checking for their presence..  
> 
> Well, I don't have a touchscreen so I can't actually verify that it
> works without these properties. The logic here is to simply translate
> the .txt file and the .txt file states that these properties are
> mandatory. But of course if people have one and can test, it would be
> good to either add the proper checks to the driver or drop these
> properties from the required list. But as far as I am concerned, it is
> too risky to do this kind of blind change in a binding file...

Fair enough!
> 
> Thanks,
> Miquèl