[PATCH v2 4/5] dt-bindings: auxdisplay: Add bindings for Hitachi HD44780

[Geert Uytterhoeven]

Add DT bindings for an Hitachi HD44780 Character LCD Controller where
its M6800 bus interface is connected to GPIOs.

Memory-mapped configurations are not yet supported.

Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
---
Memory-mapped configurations can be supported by amending the binding to
make mandatory either the {data,enable,rs}-gpios properties, or a "reg"
(and optional "reg-names") property.

As the driver doesn't support this yet, and there are different ways to
organize the register map (some wirings use different addresses for
reading and writing, to simplify bus glue logic), this is left for a
future improvement.

v2:
  - Added rationale below "---".
---
 .../devicetree/bindings/auxdisplay/hit,hd44780.txt | 44 ++++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/auxdisplay/hit,hd44780.txt

diff --git a/Documentation/devicetree/bindings/auxdisplay/hit,hd44780.txt b/Documentation/devicetree/bindings/auxdisplay/hit,hd44780.txt
new file mode 100644
index 0000000000000000..ee4054da458d412f
--- /dev/null
+++ b/Documentation/devicetree/bindings/auxdisplay/hit,hd44780.txt
@@ -0,0 +1,44 @@
+DT bindings for the Hitachi HD44780 Character LCD Controller
+
+The Hitachi HD44780 Character LCD Controller is commonly used on character LCDs
+that can display one or more lines of text. It exposes an M6800 bus interface,
+which can be used in either 4-bit or 8-bit mode.
+
+Required properties:
+  - compatible: Must contain "hit,hd44780",
+  - data-gpios: Must contain an array of either 4 or 8 GPIO specifiers,
+    referring to the GPIO pins connected to the data signal lines DB0-DB7
+    (8-bit mode) or DB4-DB7 (4-bit mode) of the LCD Controller's bus interface,
+  - enable-gpios: Must contain a GPIO specifier, referring to the GPIO pin
+    connected to the "E" (Enable) signal line of the LCD Controller's bus
+    interface,
+  - rs-gpios: Must contain a GPIO specifier, referring to the GPIO pin
+    connected to the "RS" (Register Select) signal line of the LCD Controller's
+    bus interface,
+  - display-height: Height of the display, in character cells,
+  - display-width: Width of the display, in character cells.
+
+Optional properties:
+  - rw-gpios: Must contain a GPIO specifier, referring to the GPIO pin
+    connected to the "RW" (Read/Write) signal line of the LCD Controller's bus
+    interface,
+  - backlight-gpios: Must contain a GPIO specifier, referring to the GPIO pin
+    used for enabling the LCD's backlight,
+  - internal-buffer-width: Internal buffer width (default is 40 for displays
+    with 1 or 2 lines, and display-width for displays with more than 2 lines).
+
+Example:
+
+	auxdisplay {
+		compatible = "hit,hd44780";
+
+		data-gpios = <&hc595 0 GPIO_ACTIVE_HIGH>,
+			     <&hc595 1 GPIO_ACTIVE_HIGH>,
+			     <&hc595 2 GPIO_ACTIVE_HIGH>,
+			     <&hc595 3 GPIO_ACTIVE_HIGH>;
+		enable-gpios = <&hc595 4 GPIO_ACTIVE_HIGH>;
+		rs-gpios = <&hc595 5 GPIO_ACTIVE_HIGH>;
+
+		display-height = <2>;
+		display-width = <16>;
+	};
-- 
2.7.4