[PATCH v3 1/4] devicetree: bindings: Update gpio-keys-polled with support for abs/rel axis

[Hans de Goede]

The devicetree binding for gpio-keys-polled already allows specifying
what type of events (key / rel / abs) a button generates when pressed.

But for rel / abs axis we also need to specify which value this specific
gpio represents.

One usecase is digital joysticks / direction-pads which are hooked up to
gpio, in this case we've left and right buttons which we want to map to
EV_ABS, ABS_X and we want generate events for left with a value of -1 and
for right with a value of +1 (and similar for up / down and ABS_Y).

Signed-off-by: Hans de Goede <hdegoede at redhat.com>
Acked-by: Rob Herring <robh at kernel.org>
---
Changes in v2:
-Add Rob's ack
-s/send/sent/
-Make the remarks of axis reporting a value of 0 when all buttons tied to
 that axis are released also apply to EV_REL axis
Changes in v3:
-Document that linux,input-value is a *signed* 32 bit variable and an example
 how to specify a negative value
---
 Documentation/devicetree/bindings/input/gpio-keys-polled.txt | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/input/gpio-keys-polled.txt b/Documentation/devicetree/bindings/input/gpio-keys-polled.txt
index 5b91f5a..97e2467 100644
--- a/Documentation/devicetree/bindings/input/gpio-keys-polled.txt
+++ b/Documentation/devicetree/bindings/input/gpio-keys-polled.txt
@@ -13,11 +13,18 @@ Subnode properties:
 
 	- gpios: OF device-tree gpio specification.
 	- label: Descriptive name of the key.
-	- linux,code: Keycode to emit.
+	- linux,code: Key / Axis code to emit.
 
 Optional subnode-properties:
 	- linux,input-type: Specify event type this button/key generates.
 	  If not specified defaults to <1> == EV_KEY.
+	- linux,input-value: If linux,input-type is EV_ABS or EV_REL then this
+	  value is sent for events this button generates when pressed.
+	  EV_ABS/EV_REL axis will generate an event with a value of 0 when
+	  all buttons with linux,input-type == type and linux,code == axis
+	  are released. This value is interpreted as a signed 32 bit value,
+	  e.g. to make a button generate a value of -1 use:
+	  linux,input-value = <0xffffffff>; /* -1 */
 	- debounce-interval: Debouncing interval time in milliseconds.
 	  If not specified defaults to 5.
 	- wakeup-source: Boolean, button can wake-up the system.
-- 
2.4.3