linux-kernel - Re: [PATCH v2 4/5] dt-bindings: auxdisplay: Add bindings for Hitachi HD44780

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Message-ID: <CAL_Jsq+80ut=9eGK8v2e6pW_q0yPCV-Hk25C=KeE3xZVc5ooeg@mail.gmail.com>
Date:   Mon, 20 Mar 2017 12:00:14 -0500
From:   Rob Herring <robh@...nel.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Miguel Ojeda Sandonis <miguel.ojeda.sandonis@...il.com>,
        Willy Tarreau <willy@...roxy.com>,
        Ksenija Stanojevic <ksenija.stanojevic@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Mark Rutland <mark.rutland@....com>,
        Akira Tsukamoto <akira.tsukamoto@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 4/5] dt-bindings: auxdisplay: Add bindings for Hitachi HD44780

On Mon, Mar 20, 2017 at 10:27 AM, Geert Uytterhoeven
<geert@...ux-m68k.org> wrote:
> Hi Rob, Greg,
>
> On Mon, Mar 20, 2017 at 4:15 PM, Rob Herring <robh@...nel.org> wrote:
>> On Fri, Mar 10, 2017 at 03:15:20PM +0100, Geert Uytterhoeven wrote:
>>> Add DT bindings for an Hitachi HD44780 Character LCD Controller where
>>> its M6800 bus interface is connected to GPIOs.
>>>
>>> Memory-mapped configurations are not yet supported.
>>>
>>> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
>
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/auxdisplay/hit,hd44780.txt
>
>>> +Required properties:
>>> +  - compatible: Must contain "hit,hd44780",
>>> +  - data-gpios: Must contain an array of either 4 or 8 GPIO specifiers,
>>> +    referring to the GPIO pins connected to the data signal lines DB0-DB7
>>> +    (8-bit mode) or DB4-DB7 (4-bit mode) of the LCD Controller's bus interface,
>>> +  - enable-gpios: Must contain a GPIO specifier, referring to the GPIO pin
>>> +    connected to the "E" (Enable) signal line of the LCD Controller's bus
>>> +    interface,
>>> +  - rs-gpios: Must contain a GPIO specifier, referring to the GPIO pin
>>> +    connected to the "RS" (Register Select) signal line of the LCD Controller's
>>> +    bus interface,
>>> +  - display-height: Height of the display, in character cells,
>>> +  - display-width: Width of the display, in character cells.
>>
>> display-{width,height}-chars
>
> Makes sense.
>
> Greg: As this is already in char-misc-next, shall I send an update for
> the bindings
> and the driver?
>
>>> +Optional properties:
>>> +  - rw-gpios: Must contain a GPIO specifier, referring to the GPIO pin
>>> +    connected to the "RW" (Read/Write) signal line of the LCD Controller's bus
>>> +    interface,
>>> +  - backlight-gpios: Must contain a GPIO specifier, referring to the GPIO pin
>>> +    used for enabling the LCD's backlight,
>>
>> Active state?
>
> That's typically handled via the last cell of the GPIO specifier, cfr.
> GPIO_ACTIVE_HIGH / GPIO_ACTIVE_LOW in <dt-bindings/gpio/gpio.h>.

Yes, I know. I want to be able to read the binding and validate the
dts file, so I need to know what is the correct flag.

Rob