[PATCH 00/13] Add HD44780 Character LCD support

From: Geert Uytterhoeven
Date: Mon Feb 06 2017 - 09:41:38 EST


Hi all,

Character LCDs are currently typically driven from userspace, either
directly through bit-banging, or via some kind of serial (UART/i2c)
interface.

This patch series adds kernel support for character LCDs using an
Hitachi HD44780 Character LCD Controller where its M6800 bus interface
is connected to GPIOs. It does so after extracting the character LCD
core support from the existing Parallel port LCD/Keypad Panel driver
into its own subdriver.

- Patch 1 fixes a bug in the existing panel driver,
- Patches 2-8 perform clean ups and improvements to the panel driver,
- Patch 9 extract the character LCD core support from the panel driver
into an auxdisplay charlcd subdriver,
- Patches 10-11 add new features to the character LCD core driver
(4-bit interface support and support for displays with more than 2
lines),
- Patch 12 adds DT bindings for describing HD44780 Character LCDs,
- Patch 13 adds a driver for HD44780 Character LCDs connected to
GPIOs, using the new character LCD core.

Note that Linux has other support for HD44780 Character LCDs, but none of
it is generic:
- drivers/misc/arm-charlcd.c involves a custom IP block for interfacing
to the LCD controller,
- drivers/parisc/led.c is tightly coupled to LED handling on various HP
PA-RISC machines.

This has been tested using a 20x4 character LCD with backlight, using both
8-bit and 4-bit wiring to one or two 74HC595 shift registers connected to
an SPI master controller.

Regression testing on original "panel" hardware would be appreciated.

Thanks for your comments!

Geert Uytterhoeven (13):
misc: panel: Fix LCD_FLAG_F/LCD_FLAG_N exchange
misc: panel: Remove PANEL_VERSION
misc: panel: Remove unused LCD_FLAG_S and LCD_FLAG_ID
misc: panel: Remove reference to misc device support
misc: panel: Move all suboptions into a big if section
misc: panel: Remove always-true check from panel_detach()
misc: panel: Add lcd_home() helper
misc: panel: Abstract temporary backlight handling
auxdisplay: charlcd: Extract character LCD core from misc/panel
auxdisplay: charlcd: Add support for 4-bit interfaces
auxdisplay: charlcd: Add support for displays with more than two lines
dt-bindings: auxdisplay: Add bindings for Hitachi HD44780
auxdisplay: Add HD44780 Character LCD support

.../devicetree/bindings/auxdisplay/hit,hd44780.txt | 44 ++
drivers/auxdisplay/Kconfig | 14 +
drivers/auxdisplay/Makefile | 2 +
drivers/auxdisplay/charlcd.c | 818 ++++++++++++++++++++
drivers/auxdisplay/hd44780.c | 326 ++++++++
drivers/misc/Kconfig | 45 +-
drivers/misc/panel.c | 852 +++------------------
include/misc/charlcd.h | 42 +
8 files changed, 1374 insertions(+), 769 deletions(-)
create mode 100644 Documentation/devicetree/bindings/auxdisplay/hit,hd44780.txt
create mode 100644 drivers/auxdisplay/charlcd.c
create mode 100644 drivers/auxdisplay/hd44780.c
create mode 100644 include/misc/charlcd.h

--
1.9.1

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