Hi,

I came across this searching for other proposed device tree bindings
based on what I wanted to do for Tegra.

Comments below.

On Mon, Oct 10, 2011 at 9:29 AM, Thomas Abraham
[off-list ref] wrote:

+- Keys represented as child nodes: Each key connected to the keypad
+  controller is represented as a child node to the keypad controller
+  device node and should include the following properties.
+  - keypad,row: the row number to which the key is connected.
+  - keypad,column: the column number to which the key is connected.
+  - linux,code: the key-code to be reported when the key is pressed
+    and released.

[...]

+               key_1 {
+                       keypad,row = <0>;
+                       keypad,column = <3>;
+                       linux,code = <2>;
+               };
+
+               key_2 {
+                       keypad,row = <0>;
+                       keypad,column = <4>;
+                       linux,code = <3>;
+               };
+
+               key_3 {
+                       keypad,row = <0>;
+                       keypad,column = <5>;
+                       linux,code = <4>;
+               };

The above is good if all you want to specify is a few keys. If you
want a full keyboard specification, it gets very verbose.

I would prefer a simpler binding, something along the lines of:

linux,keymap = < row col code ... >;

Where it's just an array of the above, so your example would be:
linux,keymap = < 0 3 2
                 0 4 3
                 0 5 4 >;

Same amount of data, it would be more or less as easy to read but a
_much_ more compact representation when you need to provide 100+ keys.


-Olof