Input: add input driver for polled GPIO buttons

The existing gpio-keys driver can be usable only for GPIO lines with
interrupt support. Several devices have buttons connected to a GPIO
line which is not capable to generate interrupts. This patch adds a
new input driver using the generic GPIO layer and the input-polldev
to support such buttons.

[Ben Gardiner <bengardiner@nanometrics.ca: fold code to use more
 of the original gpio_keys infrastructure; cleanups and other
 improvements.]

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Signed-off-by: Ben Gardiner <bengardiner@nanometrics.ca>
Tested-by: Ben Gardiner <bengardiner@nanometrics.ca>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/drivers/input/keyboard/Kconfig b/drivers/input/keyboard/Kconfig
index b8c51b9..3a87f3b 100644
--- a/drivers/input/keyboard/Kconfig
+++ b/drivers/input/keyboard/Kconfig
@@ -179,6 +179,22 @@
 	  To compile this driver as a module, choose M here: the
 	  module will be called gpio_keys.
 
+config KEYBOARD_GPIO_POLLED
+	tristate "Polled GPIO buttons"
+	depends on GENERIC_GPIO
+	select INPUT_POLLDEV
+	help
+	  This driver implements support for buttons connected
+	  to GPIO pins that are not capable of generating interrupts.
+
+	  Say Y here if your device has buttons connected
+	  directly to such GPIO pins.  Your board-specific
+	  setup logic must also provide a platform device,
+	  with configuration data saying which GPIOs are used.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called gpio_keys_polled.
+
 config KEYBOARD_TCA6416
 	tristate "TCA6416 Keypad Support"
 	depends on I2C