From: Lars Poeschel <poeschel@lemonage.de>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: David Airlie <airlied@linux.ie>, Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        Manuel =?ISO-8859-1?Q?Sch=F6lling?= <manuel.schoelling@gmx.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        Stafford Horne <shorne@gmail.com>,
        Christophe Leroy <christophe.leroy@c-s.fr>,
        Randy Dunlap <rdunlap@infradead.org>,
        Kate Stewart <kstewart@linuxfoundation.org>,
        Philippe Ombredanne <pombredanne@nexb.com>,
        Sean Paul <seanpaul@chromium.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        DRI Development <dri-devel@lists.freedesktop.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Linux Fbdev development list <linux-fbdev@vger.kernel.org>
Subject: Re: [PATCH] video: hd44780: Add hd44780 lcd display driver
Date: Thu, 07 Dec 2017 09:33:21 +0100
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On Wed, Dec 6, 2017 at 16:04:10 CET Geert Uytterhoeven wrote:
> Hi Lars,
> 
> On Wed, Dec 6, 2017 at 2:52 PM, Lars Poeschel <poeschel@lemonage.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@lemonage.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.

Oh! Yes, this is a very interesting idea! This would involve multiple steps 
until this would be useful for me, but I will definitely have a look at this!
So, please drop my patch for now. If for some reason in the future I find, 
that it should go upstream, I will submit it again.

BTW thanks for the hint about the hd44780 charlcd backend. I did not know 
about this. My hd44780 console driver is quite a bit old. I just found time to 
clean up, rebase, test and submit it now.

Regards,
Lars