linux-kernel - Re: [PATCH 12/13] dt-bindings: auxdisplay: Add bindings for Hitachi HD44780

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Message-ID: <20170209011130.t63w45ud55332uhy@rob-hp-laptop>
Date:   Wed, 8 Feb 2017 19:11:30 -0600
From:   Rob Herring <robh@...nel.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Miguel Ojeda Sandonis <miguel.ojeda.sandonis@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Willy Tarreau <willy@...roxy.com>,
        Ksenija Stanojevic <ksenija.stanojevic@...il.com>,
        Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>, devicetree@...r.kernel.org
Subject: Re: [PATCH 12/13] dt-bindings: auxdisplay: Add bindings for Hitachi
 HD44780

On Mon, Feb 06, 2017 at 03:38:14PM +0100, Geert Uytterhoeven wrote:
> Add DT bindings for an Hitachi HD44780 Character LCD Controller where
> its M6800 bus interface is connected to GPIOs.

Really, you should have a bit-bang M6800 bus driver and binding and then 
the binding for the LCD ctrl looks the same whether you are bit-banging 
it or not.

That's a bit more work though. Maybe you could split the binding like 
this, but keep a monolithic driver for now. The driver can just fetch 
the GPIOs from the parent (bus controller) node. And you'd have to work 
out probing the driver.

> Memory-mapped configurations are not yet supported.

I guess this would require faulting on some address and then bit-banging 
the access. That sounds fun...

Rob