[PATCH] Input: keyboard - add device tree bindings for simple key matrixes

[Olof Johansson]

On Wed, Dec 28, 2011 at 11:01 PM, Stephen Warren <swarren at nvidia.com> wrote:
> Olof Johansson wrote at Wednesday, December 28, 2011 11:34 PM:
>> On Wed, Dec 28, 2011 at 10:16 PM, Stephen Warren <swarren at nvidia.com> wrote:
>> > Olof Johansson wrote at Wednesday, December 28, 2011 3:53 PM:
>> >> From: Dmitry Torokhov <dmitry.torokhov at gmail.com>
>> >>
>> >> This adds a basic device tree binding for simple key matrix data.
>> >>
>> >> Signed-off-by: Olof Johansson <olof at lixom.net>
>> >> ---
>> >>
>> >> Based on email exchange this morning, this is a first cut at a shared
>> >> definition and helper function to parse and fill in the keymap data.
>> >>
>> >> Instead of doing the direct parsing into the final keymap format, I
>> >> chose to fill in the pdata-equivalent since that is how the OF pdata
>> >> fillers work right now if code is to be kept common with the legacy
>> >> platform_device probe interface.
>> >>
>> >> This is a prerequisite for a revised version of the tegra-kbc device
>> >> tree support that I will repost separately once this interface is stable.
>> > ...
>> >> diff --git a/Documentation/devicetree/bindings/input/matrix-keymap.txt
>> > ...
>> >> +For simple keyboards with just a few buttons, you can specify each key
>> >> +as a subnode of the keyboard controller, with 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.
>> >> +
>> >> +Example:
>> >> +
>> >> +     key_1 {
>> >> +             keypad,row = <0>;
>> >> +             keypad,column = <3>;
>> >> +             linux,code = <2>;
>> >> +     };
>> >> +
>> >> +
>> >> +For a more complex keyboard, such as a full laptop, a more compact
>> >> +binding can be used instead, with the following property directly in
>> >> +the keyboard controller node:
>> >> +
>> >> +- linux,keymap: an array of 3-cell entries containing the equivalent
>> >> +  of the three separate properties above: row, column and linux
>> >> +  key-code.
>> >
>> > Why allow two completely different bindings? Is there some deficiency
>> > to the compact binding that means it isn't suitable for all cases?
>>
>> The main reason is that the samsung keyboard driver already implements
>> the more verbose one, and allowing that binding to coexist while also
>> providing a more compact one seems like the right thing to do.
>
> Can we deprecate the Samsung format, and only allow it for that Samsung
> device (and allow both there), and require a single format for any other
> keyboard?

I'm definitely ok with that. Thomas, Grant, Rob? The code in question
is queued for 3.3, so it hasn't been out in a real release yet.

Adding Kukjin as well since it's getting merged through his tree.

> The issue here is that U-Boot wants to stay small, and having to allow
> two alternative methods to specify a keyboard is going to bloat the code;
> I expect some pushback adding DT support for just one binding by the time
> they see all the DT parsing code that's needed to do it all right.

The bloat is pretty minimal, since the parsing is simple. But yeah, I
see your point.


-Olof