Re: [PATCH 2/3] dt-bindings: input: touchscreen: add Nsiway NS2009

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

Hi Miotsuki,

On Fri, Oct 09, 2026 at 02:47:43PM +0000, Miotsuki Mizuno wrote:
> Describe the Nsiway NS2009 four-wire resistive touchscreen controller
> and the properties used by its polling driver.
>
> The controller returns 12-bit ADC coordinates. Use the common touchscreen
> properties for coordinate ranges and orientation, and allow boards to set
> the raw Z1 contact threshold through touchscreen-min-pressure. Limit that
> threshold to 1..4095 because zero cannot distinguish a released contact.
>
> Document the historical default of 80 and a board override of 150 in the
> example. The Z1 threshold is for contact detection, not calibrated
> pressure.
>
> Signed-off-by: Mizuno Miotsuki <founder@crepuse.com>
> ---
...
> +description: |
> +  The NS2009 is a four-wire resistive touchscreen controller connected over
> +  I2C. This binding describes polling operation without a pen interrupt.
> +  Coordinates are 12-bit ADC readings, not display pixel coordinates.

Devicetree bindings should describe the hardware itself rather than the
subset of features currently used by the Linux driver. According to the
NS2009 datasheet, the controller has several hardware signals and
capabilities that should be covered in the binding from the start (even
if the initial driver operates in polling mode):

  - interrupts (maxItems: 1) and wakeup-source: the controller provides
    an active-low pen interrupt output, which can remain optional for
    boards where the line is left unconnected.
  - vdd-supply and vref-supply: main power supply and external reference
    voltage regulators.
  - touchscreen-x-plate-ohms (along with touchscreen-max-pressure and
    touchscreen-fuzz-pressure): the NS2009 supports touch resistance
    calculation from Z1/Z2 and X-plate resistance.

Could you expand the binding description and properties (and show an
interrupt/supply example as well) so we do not have to revisit the
binding when IRQ or pressure support is added later?

Thanks.

-- 
Dmitry