Re: [PATCH v3 3/6] dt-bindings: add binding for Sitronix ST7586 display panels

[Noralf TrÃnnes]

Den 04.08.2017 18.51, skrev David Lechner:
> On 08/04/2017 04:48 AM, Noralf TrÃnnes wrote:
> > Den 04.08.2017 00.33, skrev David Lechner:
> > > This adds a new binding for Sitronix ST7586 display panels.
> > >
> > > Using lego as the vendor prefix in the compatible string because the 
> > > display
> > > panel I am working with is an integral part of the LEGO MINDSTORMS EV3.
> >
> > Is this display available outside of this Lego part?
> No, it is not.
>
> > If not you can remove the properties you don't need for this particular
> > display setup. Another st7586 display with a different panel would need
> > a different initialization sequence and compatible string, so we can
> > add properties when/if that happens.
>
> OK. so I will drop power-supply and backlight.

And the dc/reset gpios should be required properties since your display
won't work without them (or rather they're hardwired that way).

> Should I remove these from the driver as well? There are some panels 
> out there that could use them.[1]
>
> [1]: 
> http://www.buydisplay.com/download/manual/ERC240160-1_Series_Datasheet.pdf

Yes, because that display won't work with the driver as-is, so it's
really dead code. If someone wants to add support for that display,
they'll add the necessary code. When maintaining code for 10-20 years,
it's important to not add code that 'might' be used in the future.
Let the future take care of itself and keep the codebase slim :-)

Noralf.

> > Noralf.
> >
> > > Signed-off-by: David Lechner <david@xxxxxxxxxxxxxx>
> > > ---
> > >   .../bindings/display/sitronix,st7586.txt           | 26 
> > > ++++++++++++++++++++++
> > >   1 file changed, 26 insertions(+)
> > >   create mode 100644 
> > > Documentation/devicetree/bindings/display/sitronix,st7586.txt
> > >
> > > diff --git 
> > > a/Documentation/devicetree/bindings/display/sitronix,st7586.txt 
> > > b/Documentation/devicetree/bindings/display/sitronix,st7586.txt
> > > new file mode 100644
> > > index 0000000..dfb0b7b
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/display/sitronix,st7586.txt
> > > @@ -0,0 +1,26 @@
> > > +Sitronix ST7586 display panel
> > > +
> > > +Required properties:
> > > +- compatible:    "lego,ev3-lcd".
> > > +
> > > +The node for this driver must be a child node of a SPI controller, 
> > > hence
> > > +all mandatory properties described in ../spi/spi-bus.txt must be 
> > > specified.
> > > +
> > > +Optional properties:
> > > +- dc-gpios:    D/C pin. The presence/absence of this GPIO determines
> > > +        the panel interface operation mode (IF[3:1] pins):
> > > +        - present: IF=011 4-wire 8-bit data serial interface
> > > +        - absent:  IF=010 3-wire 9-bit data serial interface
> > > +- reset-gpios:    Reset pin
> > > +- power-supply:    A regulator node for the supply voltage.
> > > +- backlight:    phandle of the backlight device attached to the panel
> > > +- rotation:    panel rotation in degrees counter clockwise 
> > > (0,90,180,270)
> > > +
> > > +Example:
> > > +    display@0{
> > > +        compatible = "lego,ev3-lcd";
> > > +        reg = <0>;
> > > +        spi-max-frequency = <10000000>;
> > > +        dc-gpios = <&gpio 43 GPIO_ACTIVE_HIGH>;
> > > +        reset-gpios = <&gpio 80 GPIO_ACTIVE_HIGH>;
> > > +    };