extcon: gpio: Add support for active-low presence to detect pins

This patch add 'gpio_active_low' field to 'struct gpio_extcon_data'
to check whether gpio active state is 1(high) or 0(low).
Signed-off-by: NGuenter Roeck <linux@roeck-us.net>
Signed-off-by: NChanwoo Choi <cw00.choi@samsung.com>

drivers/extcon/extcon-gpio.c

@@ -34,6 +34,7 @@
 struct gpio_extcon_data {
 	struct extcon_dev edev;
 	unsigned gpio;
+	bool gpio_active_low;
 	const char *state_on;
 	const char *state_off;
 	int irq;
@@ -49,6 +50,8 @@ static void gpio_extcon_work(struct work_struct *work)
 			     work);
 
 	state = gpio_get_value(data->gpio);
+	if (data->gpio_active_low)
+		state = !state;
 	extcon_set_state(&data->edev, state);
 }
 
@@ -96,6 +99,7 @@ static int gpio_extcon_probe(struct platform_device *pdev)
 
 	extcon_data->edev.name = pdata->name;
 	extcon_data->gpio = pdata->gpio;
+	extcon_data->gpio_active_low = pdata->gpio_active_low;
 	extcon_data->state_on = pdata->state_on;
 	extcon_data->state_off = pdata->state_off;
 	if (pdata->state_on && pdata->state_off)

include/linux/extcon/extcon-gpio.h

@@ -27,6 +27,9 @@
  * struct gpio_extcon_platform_data - A simple GPIO-controlled extcon device.
  * @name:		The name of this GPIO extcon device.
  * @gpio:		Corresponding GPIO.
+ * @gpio_active_low:	Boolean describing whether gpio active state is 1 or 0
+ *			If true, low state of gpio means active.
+ *			If false, high state of gpio means active.
  * @debounce:		Debounce time for GPIO IRQ in ms.
  * @irq_flags:		IRQ Flags (e.g., IRQF_TRIGGER_LOW).
  * @state_on:		print_state is overriden with state_on if attached.
@@ -41,6 +44,7 @@
 struct gpio_extcon_platform_data {
 	const char *name;
 	unsigned gpio;
+	bool gpio_active_low;
 	unsigned long debounce;
 	unsigned long irq_flags;