linux-kernel - Re: [PATCH] video: hd44780: Add hd44780 lcd display driver

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Message-ID: <CAMuHMdUn-wx7YC=QWazb4e-vJGts8iXbkC64NYiEjha-kQPKLg@mail.gmail.com>
Date:   Wed, 6 Dec 2017 16:04:10 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Lars Poeschel <poeschel@...onage.de>
Cc:     David Airlie <airlied@...ux.ie>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Manuel Schölling <manuel.schoelling@....de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Stafford Horne <shorne@...il.com>,
        Christophe Leroy <christophe.leroy@....fr>,
        Randy Dunlap <rdunlap@...radead.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Sean Paul <seanpaul@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linux Fbdev development list <linux-fbdev@...r.kernel.org>
Subject: Re: [PATCH] video: hd44780: Add hd44780 lcd display driver

Hi Lars,

On Wed, Dec 6, 2017 at 2:52 PM, Lars Poeschel <poeschel@...onage.de> wrote:
> This adds a console driver for hd44780 based character lcd displays and
> clones. The driver currently supports 20x4 character displays with
> character ROMs A00 and A02.
> The hardware wirings to the display have to be supplied to the kernel in
> the devicetree. The binding doc has the necessary information.
> There are also tons of these cheap displays sold with a serial
> interface. Many of them use a simple pcf8574 gpio expanders. An example
> for using that kind of display is also in the binding doc.
>
> Signed-off-by: Lars Poeschel <poeschel@...onage.de>

Thanks for your patch!

> ---
>  .../bindings/video/console/hd44780con.txt          |  42 ++
>  drivers/video/console/Kconfig                      |  13 +
>  drivers/video/console/Makefile                     |   1 +
>  drivers/video/console/hd44780con.c                 | 676 +++++++++++++++++++++

I'm wondering if you could implement this on top of the existing charlcd
framework:

    drivers/auxdisplay/charlcd.c
    include/misc/charlcd.h

which can use the existing hd44780 backend:

    Documentation/devicetree/bindings/auxdisplay/hit,hd44780.txt
    drivers/auxdisplay/hd44780.c

That way it can be used on other character LCDs, like the one supported by
drivers/auxdisplay/panel.c.

Thanks!

P.S. I did something similar a long time ago, cfr.
     https://github.com/geertu/hd44780/blob/master/lcdcon.c

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds