extcon: adc_jack: adc-jack driver to support 3.5 pi or simliar devices

External connector devices that decides connection information based on
ADC values may use adc-jack device driver. The user simply needs to
provide a table of adc range and connection states. Then, extcon
framework will automatically notify others.

Changes in V1:
added Lars-Peter Clausen suggested changes:
Using macros to get rid of boiler plate code such as devm_kzalloc
and module_platform_driver.Other changes suggested are related to
coding guidelines.

Changes in V2:
Removed some unnecessary checks and changed the way we are un-regitering
extcon and freeing the irq while removing.

Changes in V3:
Renamed the files to comply with extcon naming.

Changes in V4:
Added the cancel_work_sync during removing of driver.

Changes in V5:
Added the dependency of IIO in Kconfig.

Changes in V6:
Some nitpicks related to naming.

Changes in this version:
V6 patch version patch broke the build:
ERROR: "extcon_cable_name" [drivers/extcon/extcon-adc-jack.ko] undefined!

Fixed it in this version.
Acked-by: Jonathan Cameron <jic23@kernel.org>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: anish kumar <anish.singh@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/extcon/Kconfig

@@ -21,6 +21,12 @@ config EXTCON_GPIO
 	  Say Y here to enable GPIO based extcon support. Note that GPIO
 	  extcon supports single state per extcon instance.
 
+config EXTCON_ADC_JACK
+	tristate "ADC Jack extcon support"
+	depends on IIO
+	help
+	  Say Y here to enable extcon device driver based on ADC values.
+
 config EXTCON_MAX77693
 	tristate "MAX77693 EXTCON Support"
 	depends on MFD_MAX77693

drivers/extcon/Makefile

@@ -4,6 +4,7 @@
 
 obj-$(CONFIG_EXTCON)		+= extcon-class.o
 obj-$(CONFIG_EXTCON_GPIO)	+= extcon-gpio.o
+obj-$(CONFIG_EXTCON_ADC_JACK)	+= extcon-adc-jack.o
 obj-$(CONFIG_EXTCON_MAX77693)	+= extcon-max77693.o
 obj-$(CONFIG_EXTCON_MAX8997)	+= extcon-max8997.o
 obj-$(CONFIG_EXTCON_ARIZONA)	+= extcon-arizona.o

drivers/extcon/extcon-adc-jack.c

+/*
+ * drivers/extcon/extcon-adc-jack.c
+ *
+ * Analog Jack extcon driver with ADC-based detection capability.
+ *
+ * Copyright (C) 2012 Samsung Electronics
+ * MyungJoo Ham <myungjoo.ham@samsung.com>
+ *
+ * Modified for calling to IIO to get adc by <anish.singh@samsung.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#include <linux/slab.h>
+#include <linux/device.h>
+#include <linux/platform_device.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/workqueue.h>
+#include <linux/iio/consumer.h>
+#include <linux/extcon/extcon-adc-jack.h>
+#include <linux/extcon.h>
+
+/**
+ * struct adc_jack_data - internal data for adc_jack device driver
+ * @edev        - extcon device.
+ * @cable_names - list of supported cables.
+ * @num_cables  - size of cable_names.
+ * @adc_conditions       - list of adc value conditions.
+ * @num_conditions       - size of adc_conditions.
+ * @irq         - irq number of attach/detach event (0 if not exist).
+ * @handling_delay      - interrupt handler will schedule extcon event
+ *                      handling at handling_delay jiffies.
+ * @handler     - extcon event handler called by interrupt handler.
+ * @chan       - iio channel being queried.
+ */
+struct adc_jack_data {
+	struct extcon_dev edev;
+
+	const char **cable_names;
+	int num_cables;
+	struct adc_jack_cond *adc_conditions;
+	int num_conditions;
+
+	int irq;
+	unsigned long handling_delay; /* in jiffies */
+	struct delayed_work handler;
+
+	struct iio_channel *chan;
+};
+
+static void adc_jack_handler(struct work_struct *work)
+{
+	struct adc_jack_data *data = container_of(to_delayed_work(work),
+			struct adc_jack_data,
+			handler);
+	u32 state = 0;
+	int ret, adc_val;
+	int i;
+
+	ret = iio_read_channel_raw(data->chan, &adc_val);
+	if (ret < 0) {
+		dev_err(data->edev.dev, "read channel() error: %d\n", ret);
+		return;
+	}
+
+	/* Get state from adc value with adc_conditions */
+	for (i = 0; i < data->num_conditions; i++) {
+		struct adc_jack_cond *def = &data->adc_conditions[i];
+		if (!def->state)
+			break;
+		if (def->min_adc <= adc_val && def->max_adc >= adc_val) {
+			state = def->state;
+			break;
+		}
+	}
+	/* if no def has met, it means state = 0 (no cables attached) */
+
+	extcon_set_state(&data->edev, state);
+}
+
+static irqreturn_t adc_jack_irq_thread(int irq, void *_data)
+{
+	struct adc_jack_data *data = _data;
+
+	schedule_delayed_work(&data->handler, data->handling_delay);
+	return IRQ_HANDLED;
+}
+
+static int __devinit adc_jack_probe(struct platform_device *pdev)
+{
+	struct adc_jack_data *data;
+	struct adc_jack_pdata *pdata = pdev->dev.platform_data;
+	int i, err = 0;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->edev.name = pdata->name;
+
+	if (!pdata->cable_names) {
+		err = -EINVAL;
+		dev_err(&pdev->dev, "error: cable_names not defined.\n");
+		goto out;
+	}
+
+	data->edev.supported_cable = pdata->cable_names;
+
+	/* Check the length of array and set num_cables */
+	for (i = 0; data->edev.supported_cable[i]; i++)
+		;
+	if (i == 0 || i > SUPPORTED_CABLE_MAX) {
+		err = -EINVAL;
+		dev_err(&pdev->dev, "error: pdata->cable_names size = %d\n",
+				i - 1);
+		goto out;
+	}
+	data->num_cables = i;
+
+	if (!pdata->adc_conditions ||
+			!pdata->adc_conditions[0].state) {
+		err = -EINVAL;
+		dev_err(&pdev->dev, "error: adc_conditions not defined.\n");
+		goto out;
+	}
+	data->adc_conditions = pdata->adc_conditions;
+
+	/* Check the length of array and set num_conditions */
+	for (i = 0; data->adc_conditions[i].state; i++)
+		;
+	data->num_conditions = i;
+
+	data->chan = iio_channel_get(dev_name(&pdev->dev),
+			pdata->consumer_channel);
+	if (IS_ERR(data->chan)) {
+		err = PTR_ERR(data->chan);
+		goto out;
+	}
+
+	data->handling_delay = msecs_to_jiffies(pdata->handling_delay_ms);
+
+	INIT_DELAYED_WORK_DEFERRABLE(&data->handler, adc_jack_handler);
+
+	platform_set_drvdata(pdev, data);
+
+	err = extcon_dev_register(&data->edev, &pdev->dev);
+	if (err)
+		goto out;
+
+	data->irq = platform_get_irq(pdev, 0);
+	if (!data->irq) {
+		dev_err(&pdev->dev, "platform_get_irq failed\n");
+		err = -ENODEV;
+		goto err_irq;
+	}
+
+	err = request_any_context_irq(data->irq, adc_jack_irq_thread,
+			pdata->irq_flags, pdata->name, data);
+
+	if (err) {
+		dev_err(&pdev->dev, "error: irq %d\n", data->irq);
+		err = -EINVAL;
+		goto err_irq;
+	}
+
+	goto out;
+
+err_irq:
+	extcon_dev_unregister(&data->edev);
+out:
+	return err;
+}
+
+static int __devexit adc_jack_remove(struct platform_device *pdev)
+{
+	struct adc_jack_data *data = platform_get_drvdata(pdev);
+
+	free_irq(data->irq, data);
+	cancel_work_sync(&data->handler.work);
+	extcon_dev_unregister(&data->edev);
+
+	return 0;
+}
+
+static struct platform_driver adc_jack_driver = {
+	.probe          = adc_jack_probe,
+	.remove         = __devexit_p(adc_jack_remove),
+	.driver         = {
+		.name   = "adc-jack",
+		.owner  = THIS_MODULE,
+	},
+};
+
+module_platform_driver(adc_jack_driver);

include/linux/extcon/extcon-adc-jack.h

+/*
+ * include/linux/extcon/extcon-adc-jack.h
+ *
+ * Analog Jack extcon driver with ADC-based detection capability.
+ *
+ * Copyright (C) 2012 Samsung Electronics
+ * MyungJoo Ham <myungjoo.ham@samsung.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#ifndef _EXTCON_ADC_JACK_H_
+#define _EXTCON_ADC_JACK_H_ __FILE__
+
+#include <linux/module.h>
+#include <linux/extcon.h>
+
+/**
+ * struct adc_jack_cond - condition to use an extcon state
+ * @state      - the corresponding extcon state (if 0, this struct denotes
+ *             the last adc_jack_cond element among the array)
+ * @min_adc    - min adc value for this condition
+ * @max_adc    - max adc value for this condition
+ *
+ * For example, if { .state = 0x3, .min_adc = 100, .max_adc = 200}, it means
+ * that if ADC value is between (inclusive) 100 and 200, than the cable 0 and
+ * 1 are attached (1<<0 | 1<<1 == 0x3)
+ *
+ * Note that you don't need to describe condition for "no cable attached"
+ * because when no adc_jack_cond is met, state = 0 is automatically chosen.
+ */
+struct adc_jack_cond {
+	u32 state; /* extcon state value. 0 if invalid */
+	u32 min_adc;
+	u32 max_adc;
+};
+
+/**
+ * struct adc_jack_pdata - platform data for adc jack device.
+ * @name       - name of the extcon device. If null, "adc-jack" is used.
+ * @consumer_channel - Unique name to identify the channel on the consumer
+ *                   side. This typically describes the channels used within
+ *                   the consumer. E.g. 'battery_voltage'
+ * @cable_names        - array of cable names ending with null.
+ * @adc_contitions     - array of struct adc_jack_cond conditions ending
+ *                     with .state = 0 entry. This describes how to decode
+ *                     adc values into extcon state.
+ * @irq_flags  - irq flags used for the @irq
+ * @handling_delay_ms  - in some devices, we need to read ADC value some
+ *                     milli-seconds after the interrupt occurs. You may
+ *                     describe such delays with @handling_delay_ms, which
+ *                     is rounded-off by jiffies.
+ */
+struct adc_jack_pdata {
+	const char *name;
+	const char *consumer_channel;
+	/*
+	 * The last entry should be NULL
+	 */
+	const char **cable_names;
+	/* The last entry's state should be 0 */
+	struct adc_jack_cond *adc_conditions;
+
+	unsigned long irq_flags;
+	unsigned long handling_delay_ms; /* in ms */
+};
+
+#endif /* _EXTCON_ADC_JACK_H */