Input: add support for generic GPIO-based matrix keypad

Original patch by Marek Vasut, modified by Eric in:

1. use delayed work to simplify the debouncing
2. combine col_polarity/row_polarity into a single active_low field
3. use a generic bit array based XOR algorithm to detect key
   press/release, which should make the column assertion time
   shorter and code a bit cleaner
4. remove the ALT_FN handling, which is no way generic, the ALT_FN
   key should be treated as no different from other keys, and
   translation will be done by user space by commands like 'loadkeys'.
5. explicitly disable row IRQs and flush potential pending work,
   and schedule an immediate scan after resuming as suggested
   by Uli Luckas
6. incorporate review comments from many others

Patch tested on Littleton/PXA310 (though PXA310 has a dedicate keypad
controller, I have to configure those pins as generic GPIO to use this
driver, works quite well, though), and Sharp Zaurus model SL-C7x0
and SL-C1000.

[dtor@mail.ru: fix error unwinding path, support changing keymap
 from userspace]
Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
Reviewed-by: Trilok Soni <soni.trilok@gmail.com>
Reviewed-by: Uli Luckas <u.luckas@road.de>
Reviewed-by: Russell King <linux@arm.linux.org.uk>
Reviewed-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Eric Miao <eric.miao@marvell.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/keyboard/Kconfig

@@ -158,7 +158,16 @@ config KEYBOARD_GPIO
 	  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.
+	  module will be called gpio_keys.
+
+config KEYBOARD_MATRIX
+	tristate "GPIO driven matrix keypad support"
+	depends on GENERIC_GPIO
+	help
+	  Enable support for GPIO driven matrix keypad.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called matrix_keypad.
 
 config KEYBOARD_HIL_OLD
 	tristate "HP HIL keyboard support (simple driver)"
@@ -254,7 +263,7 @@ config KEYBOARD_PXA27x
 	tristate "PXA27x/PXA3xx keypad support"
 	depends on PXA27x || PXA3xx
 	help
-	  Enable support for PXA27x/PXA3xx keypad controller
+	  Enable support for PXA27x/PXA3xx keypad controller.
 
 	  To compile this driver as a module, choose M here: the
 	  module will be called pxa27x_keypad.

drivers/input/keyboard/Makefile

@@ -20,6 +20,7 @@ obj-$(CONFIG_KEYBOARD_LKKBD)		+= lkkbd.o
 obj-$(CONFIG_KEYBOARD_LM8323)		+= lm8323.o
 obj-$(CONFIG_KEYBOARD_LOCOMO)		+= locomokbd.o
 obj-$(CONFIG_KEYBOARD_MAPLE)		+= maple_keyb.o
+obj-$(CONFIG_KEYBOARD_MATRIX)		+= matrix_keypad.o
 obj-$(CONFIG_KEYBOARD_NEWTON)		+= newtonkbd.o
 obj-$(CONFIG_KEYBOARD_OMAP)		+= omap-keypad.o
 obj-$(CONFIG_KEYBOARD_PXA27x)		+= pxa27x_keypad.o