Staging: IIO: Proof of concept gpio trigger

Simple example of how a gpio trigger driver would work.
Things to be added include interupt type control (high, low).
Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/trigger/Kconfig

@@ -12,4 +12,10 @@ config IIO_PERIODIC_RTC_TRIGGER
 	    Provides support for using periodic capable real time
 	    clocks as IIO triggers.
 
+config IIO_GPIO_TRIGGER
+	tristate "GPIO trigger"
+	depends on GENERIC_GPIO
+	help
+	    Provides support for using GPIO pins as IIO triggers.
+
 endif # IIO_TRIGGER

drivers/staging/iio/trigger/Makefile

@@ -2,4 +2,4 @@
 # Makefile for triggers not associated with iio-devices
 #
 obj-$(CONFIG_IIO_PERIODIC_RTC_TRIGGER) += iio-trig-periodic-rtc.o
-
+obj-$(CONFIG_IIO_GPIO_TRIGGER) += iio-trig-gpio.o
\ No newline at end of file

drivers/staging/iio/trigger/iio-trig-gpio.c

+/*
+ * Industrial I/O - gpio based trigger support
+ *
+ * Copyright (c) 2008 Jonathan Cameron
+ *
+ * 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.
+ *
+ * Currently this is more of a functioning proof of concept that a fully
+ * fledged trigger driver.
+ *
+ * TODO:
+ *
+ * Add board config elements to allow specification of startup settings.
+ * Add configuration settings (irq type etc)
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/interrupt.h>
+#include <linux/gpio.h>
+
+#include "../iio.h"
+#include "../trigger.h"
+
+LIST_HEAD(iio_gpio_trigger_list);
+DEFINE_MUTEX(iio_gpio_trigger_list_lock);
+
+struct iio_gpio_trigger_info {
+	struct mutex in_use;
+	int gpio;
+};
+/*
+ * Need to reference count these triggers and only enable gpio interrupts
+ * as appropriate.
+ */
+
+/* So what functionality do we want in here?... */
+/* set high / low as interrupt type? */
+
+static irqreturn_t iio_gpio_trigger_poll(int irq, void *private)
+{
+	iio_trigger_poll(private);
+	return IRQ_HANDLED;
+}
+
+DEVICE_ATTR(name, S_IRUGO, iio_trigger_read_name, NULL);
+
+static struct attribute *iio_gpio_trigger_attrs[] = {
+	&dev_attr_name.attr,
+	NULL,
+};
+
+static const struct attribute_group iio_gpio_trigger_attr_group = {
+	.attrs = iio_gpio_trigger_attrs,
+};
+
+static int iio_gpio_trigger_probe(struct platform_device *dev)
+{
+	int *pdata = dev->dev.platform_data;
+	struct iio_gpio_trigger_info *trig_info;
+	struct iio_trigger *trig, *trig2;
+	int i, irq, ret = 0;
+	if (!pdata) {
+		printk(KERN_ERR "No IIO gpio trigger platform data found\n");
+		goto error_ret;
+	}
+	for (i = 0;; i++) {
+		if (!gpio_is_valid(pdata[i]))
+			break;
+		trig = iio_allocate_trigger();
+		if (!trig) {
+			ret = -ENOMEM;
+			goto error_free_completed_registrations;
+		}
+
+		trig_info = kzalloc(sizeof(*trig_info), GFP_KERNEL);
+		if (!trig_info) {
+			ret = -ENOMEM;
+			goto error_put_trigger;
+		}
+		trig->control_attrs = &iio_gpio_trigger_attr_group;
+		trig->private_data = trig_info;
+		trig_info->gpio = pdata[i];
+		trig->owner = THIS_MODULE;
+		trig->name = kmalloc(IIO_TRIGGER_NAME_LENGTH, GFP_KERNEL);
+		if (!trig->name) {
+			ret = -ENOMEM;
+			goto error_free_trig_info;
+		}
+		snprintf((char *)trig->name,
+			 IIO_TRIGGER_NAME_LENGTH,
+			 "gpiotrig%d",
+			 pdata[i]);
+		ret = gpio_request(trig_info->gpio, trig->name);
+		if (ret)
+			goto error_free_name;
+
+		ret = gpio_direction_input(trig_info->gpio);
+		if (ret)
+			goto error_release_gpio;
+
+		irq = gpio_to_irq(trig_info->gpio);
+		if (irq < 0) {
+			ret = irq;
+			goto error_release_gpio;
+		}
+
+		ret = request_irq(irq, iio_gpio_trigger_poll,
+				  IRQF_TRIGGER_RISING,
+				  trig->name,
+				  trig);
+		if (ret)
+			goto error_release_gpio;
+
+		ret = iio_trigger_register(trig);
+		if (ret)
+			goto error_release_irq;
+
+		list_add_tail(&trig->alloc_list, &iio_gpio_trigger_list);
+
+	}
+	return 0;
+
+/* First clean up the partly allocated trigger */
+error_release_irq:
+	free_irq(irq, trig);
+error_release_gpio:
+	gpio_free(trig_info->gpio);
+error_free_name:
+	kfree(trig->name);
+error_free_trig_info:
+	kfree(trig_info);
+error_put_trigger:
+	iio_put_trigger(trig);
+error_free_completed_registrations:
+	/* The rest should have been added to the iio_gpio_trigger_list */
+	list_for_each_entry_safe(trig,
+				 trig2,
+				 &iio_gpio_trigger_list,
+				 alloc_list) {
+		trig_info = trig->private_data;
+		free_irq(gpio_to_irq(trig_info->gpio), trig);
+		gpio_free(trig_info->gpio);
+		kfree(trig->name);
+		kfree(trig_info);
+		iio_trigger_unregister(trig);
+	}
+
+error_ret:
+	return ret;
+}
+
+static int iio_gpio_trigger_remove(struct platform_device *dev)
+{
+	struct iio_trigger *trig, *trig2;
+	struct iio_gpio_trigger_info *trig_info;
+
+	mutex_lock(&iio_gpio_trigger_list_lock);
+	list_for_each_entry_safe(trig,
+				 trig2,
+				 &iio_gpio_trigger_list,
+				 alloc_list) {
+		trig_info = trig->private_data;
+		iio_trigger_unregister(trig);
+		free_irq(gpio_to_irq(trig_info->gpio), trig);
+		gpio_free(trig_info->gpio);
+		kfree(trig->name);
+		kfree(trig_info);
+		iio_put_trigger(trig);
+	}
+	mutex_unlock(&iio_gpio_trigger_list_lock);
+
+	return 0;
+}
+
+static struct platform_driver iio_gpio_trigger_driver = {
+	.probe = iio_gpio_trigger_probe,
+	.remove = iio_gpio_trigger_remove,
+	.driver = {
+		.name = "iio_gpio_trigger",
+		.owner = THIS_MODULE,
+	},
+};
+
+static int __init iio_gpio_trig_init(void)
+{
+	return platform_driver_register(&iio_gpio_trigger_driver);
+}
+module_init(iio_gpio_trig_init);
+
+static void __exit iio_gpio_trig_exit(void)
+{
+	platform_driver_unregister(&iio_gpio_trigger_driver);
+}
+module_exit(iio_gpio_trig_exit);
+
+MODULE_AUTHOR("Jonathan Cameron <jic23@cam.ac.uk>");
+MODULE_DESCRIPTION("Example gpio trigger for the iio subsystem");
+MODULE_LICENSE("GPL v2");