Hi Geert.
On Mon, Jan 20, 2020 at 11:10:37AM +0100, Geert Uytterhoeven wrote:
Hi Sam,
(stumbled on this accidentally)
On Thu, Aug 2, 2018 at 9:46 PM Sam Ravnborg sam@ravnborg.org 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@ravnborg.org
--- /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---------------------------- IC | Reset | SP ---------------------------- PU | 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 :-)
It is on my TODO list to make a mipi-dbi driver that in the future replaces the auxdisplay driver for hd44780. But that TODO list have a growing tendency. It seems that pretending to be co-maintainer on panel/ stuff alone can take up most of my DRM time.
I hope Paul will contribute the i8080 support to drm_mipi_dbi, at least he mentioned he planned to work on this.
Sam