Extcon: support generic GPIO extcon driver

The generic GPIO extcon driver (an external connector device based on
GPIO control) and imported from Android kernel.

switch: switch class and GPIO drivers. (splitted)
Author: Mike Lockwood <lockwood@android.com>

switch: gpio: Don't call request_irq with interrupts disabled
Author: Arve Hjønnevåg <arve@android.com>

switch_gpio: Add missing #include <linux/interrupt.h>
Author: Mike Lockwood <lockwood@android.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

--
Changed from v7:
- Style updates mentioned by Stephen Boyd and Mark Brown
Changed from v5:
- Splitted at v5 from the main extcon patch.
- Added debounce time for irq handlers.
- Use request_any_context_irq instead of request_irq
- User needs to specify irq flags for GPIO interrupts (was fixed to
IRQF_TRIGGER_LOW before)
- Use module_platform_driver().
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/extcon/Kconfig

@@ -14,4 +14,11 @@ if EXTCON
 
 comment "Extcon Device Drivers"
 
+config EXTCON_GPIO
+	tristate "GPIO extcon support"
+	depends on GENERIC_GPIO
+	help
+	  Say Y here to enable GPIO based extcon support. Note that GPIO
+	  extcon supports single state per extcon instance.
+
 endif # MULTISTATE_SWITCH

drivers/extcon/Makefile

@@ -3,3 +3,4 @@
 #
 
 obj-$(CONFIG_EXTCON)		+= extcon_class.o
+obj-$(CONFIG_EXTCON_GPIO)	+= extcon_gpio.o

drivers/extcon/extcon_gpio.c

+/*
+ *  drivers/extcon/extcon_gpio.c
+ *
+ *  Single-state GPIO extcon driver based on extcon class
+ *
+ * Copyright (C) 2008 Google, Inc.
+ * Author: Mike Lockwood <lockwood@android.com>
+ *
+ * Modified by MyungJoo Ham <myungjoo.ham@samsung.com> to support extcon
+ * (originally switch class is supported)
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+*/
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/extcon.h>
+#include <linux/workqueue.h>
+#include <linux/gpio.h>
+#include <linux/extcon.h>
+#include <linux/extcon/extcon_gpio.h>
+
+struct gpio_extcon_data {
+	struct extcon_dev edev;
+	unsigned gpio;
+	const char *state_on;
+	const char *state_off;
+	int irq;
+	struct delayed_work work;
+	unsigned long debounce_jiffies;
+};
+
+static void gpio_extcon_work(struct work_struct *work)
+{
+	int state;
+	struct gpio_extcon_data	*data =
+		container_of(to_delayed_work(work), struct gpio_extcon_data,
+			     work);
+
+	state = gpio_get_value(data->gpio);
+	extcon_set_state(&data->edev, state);
+}
+
+static irqreturn_t gpio_irq_handler(int irq, void *dev_id)
+{
+	struct gpio_extcon_data *extcon_data = dev_id;
+
+	schedule_delayed_work(&extcon_data->work,
+			      extcon_data->debounce_jiffies);
+	return IRQ_HANDLED;
+}
+
+static ssize_t extcon_gpio_print_state(struct extcon_dev *edev, char *buf)
+{
+	struct gpio_extcon_data	*extcon_data =
+		container_of(edev, struct gpio_extcon_data, edev);
+	const char *state;
+	if (extcon_get_state(edev))
+		state = extcon_data->state_on;
+	else
+		state = extcon_data->state_off;
+
+	if (state)
+		return sprintf(buf, "%s\n", state);
+	return -EINVAL;
+}
+
+static int __devinit gpio_extcon_probe(struct platform_device *pdev)
+{
+	struct gpio_extcon_platform_data *pdata = pdev->dev.platform_data;
+	struct gpio_extcon_data *extcon_data;
+	int ret = 0;
+
+	if (!pdata)
+		return -EBUSY;
+	if (!pdata->irq_flags) {
+		dev_err(&pdev->dev, "IRQ flag is not specified.\n");
+		return -EINVAL;
+	}
+
+	extcon_data = devm_kzalloc(&pdev->dev, sizeof(struct gpio_extcon_data),
+				   GFP_KERNEL);
+	if (!extcon_data)
+		return -ENOMEM;
+
+	extcon_data->edev.name = pdata->name;
+	extcon_data->gpio = pdata->gpio;
+	extcon_data->state_on = pdata->state_on;
+	extcon_data->state_off = pdata->state_off;
+	if (pdata->state_on && pdata->state_off)
+		extcon_data->edev.print_state = extcon_gpio_print_state;
+	extcon_data->debounce_jiffies = msecs_to_jiffies(pdata->debounce);
+
+	ret = extcon_dev_register(&extcon_data->edev, &pdev->dev);
+	if (ret < 0)
+		goto err_extcon_dev_register;
+
+	ret = gpio_request_one(extcon_data->gpio, GPIOF_DIR_IN, pdev->name);
+	if (ret < 0)
+		goto err_request_gpio;
+
+	INIT_DELAYED_WORK(&extcon_data->work, gpio_extcon_work);
+
+	extcon_data->irq = gpio_to_irq(extcon_data->gpio);
+	if (extcon_data->irq < 0) {
+		ret = extcon_data->irq;
+		goto err_detect_irq_num_failed;
+	}
+
+	ret = request_any_context_irq(extcon_data->irq, gpio_irq_handler,
+				      pdata->irq_flags, pdev->name,
+				      extcon_data);
+	if (ret < 0)
+		goto err_request_irq;
+
+	/* Perform initial detection */
+	gpio_extcon_work(&extcon_data->work.work);
+
+	return 0;
+
+err_request_irq:
+err_detect_irq_num_failed:
+	gpio_free(extcon_data->gpio);
+err_request_gpio:
+	extcon_dev_unregister(&extcon_data->edev);
+err_extcon_dev_register:
+	devm_kfree(&pdev->dev, extcon_data);
+
+	return ret;
+}
+
+static int __devexit gpio_extcon_remove(struct platform_device *pdev)
+{
+	struct gpio_extcon_data *extcon_data = platform_get_drvdata(pdev);
+
+	cancel_delayed_work_sync(&extcon_data->work);
+	gpio_free(extcon_data->gpio);
+	extcon_dev_unregister(&extcon_data->edev);
+	devm_kfree(&pdev->dev, extcon_data);
+
+	return 0;
+}
+
+static struct platform_driver gpio_extcon = {
+	.probe		= gpio_extcon_probe,
+	.remove		= __devexit_p(gpio_extcon_remove),
+	.driver		= {
+		.name	= "extcon-gpio",
+		.owner	= THIS_MODULE,
+	},
+};
+
+module_platform_driver(gpio_extcon);
+
+MODULE_AUTHOR("Mike Lockwood <lockwood@android.com>");
+MODULE_DESCRIPTION("GPIO extcon driver");
+MODULE_LICENSE("GPL");

include/linux/extcon/extcon_gpio.h

+/*
+ *  External connector (extcon) class generic GPIO driver
+ *
+ * Copyright (C) 2012 Samsung Electronics
+ * Author: MyungJoo Ham <myungjoo.ham@samsung.com>
+ *
+ * based on switch class driver
+ * Copyright (C) 2008 Google, Inc.
+ * Author: Mike Lockwood <lockwood@android.com>
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+*/
+#ifndef __EXTCON_GPIO_H__
+#define __EXTCON_GPIO_H__ __FILE__
+
+#include <linux/extcon.h>
+
+/**
+ * struct gpio_extcon_platform_data - A simple GPIO-controlled extcon device.
+ * @name	The name of this GPIO extcon device.
+ * @gpio	Corresponding GPIO.
+ * @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. If Null,
+ *		default method of extcon class is used.
+ * @state_off	print_state is overriden with state_on if dettached. If Null,
+ *		default method of extcon class is used.
+ *
+ * Note that in order for state_on or state_off to be valid, both state_on
+ * and state_off should be not NULL. If at least one of them is NULL,
+ * the print_state is not overriden.
+ */
+struct gpio_extcon_platform_data {
+	const char *name;
+	unsigned gpio;
+	unsigned long debounce;
+	unsigned long irq_flags;
+
+	/* if NULL, "0" or "1" will be printed */
+	const char *state_on;
+	const char *state_off;
+};
+
+#endif /* __EXTCON_GPIO_H__ */