Hi Sam,
On Mon, Jan 20, 2020 at 7:48 PM Sam Ravnborg <sam@xxxxxxxxxxxx> wrote:
> On Mon, Jan 20, 2020 at 11:10:37AM +0100, Geert Uytterhoeven wrote:
> > On Thu, Aug 2, 2018 at 9:46 PM Sam Ravnborg <sam@xxxxxxxxxxxx> wrote:
> > > The pardata supports implement a simple bus for devices
> > > that are connected using a parallel bus driven by GPIOs.
> > > The is often used in combination with simple displays
> > > that is often seen in older embedded designs.
> > > There is a demand for this support also in the linux
> > > kernel for HW designs that uses these kind of displays.
> > >
> > > The pardata bus uses a platfrom_driver that when probed
> > > creates devices for all child nodes in the DT,
> > > which are then supposed to be handled by pardata_drivers.
> > >
> > > Signed-off-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
> >
> > > --- /dev/null
> > > +++ b/Documentation/driver-api/pardata.rst
> > > @@ -0,0 +1,60 @@
> > > +.. SPDX-License-Identifier: GPL-2.0
> > > +
> > > +=========================
> > > +Parallel Data Bus/Drivers
> > > +=========================
> > > +
> > > +Displays may be connected using a simple parallel bus.
> > > +This is often seen in embedded systems with a simple MCU, but is also
> > > +used in Linux based systems to a small extent.
> > > +
> > > +The bus looks like this:
> > > +
> > > +.. code-block:: none
> > > +
> > > + ----+
> > > + | DB0-DB7 or DB4-DB7 +----
> > > + ===/========================
> > > + | E - enable | D
> > > + ---------------------------- I
> > > + C | Reset | S
> > > + P ---------------------------- P
> > > + U | Read/Write (one or two) | L
> > > + ---------------------------- A
> > > + | RS - instruction/data | Y
> > > + ----------------------------
> > > + | +----
> > > + ----+
> >
> > Oh, cool! Looks like this can be used by the hd44780 driver.
> >
> > Documentation/devicetree/bindings/auxdisplay/hit,hd44780.txt
> > drivers/auxdisplay/hd44780.c
>
> This patchset was from a time when I knew next to nothing about DRM.
> Now I am just confused on a different level :-)
The more you know, the more you realize what you don't know ;-)
> It is on my TODO list to make a mipi-dbi driver that in the future
> replaces the auxdisplay driver for hd44780.
Please note that hd44780 is a character controller.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
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
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