[RFC] gpio: consumer: new virtual driver

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index e382dfebad7c..ddae605341fd 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1796,6 +1796,13 @@  config GPIO_SIM
 	  This enables the GPIO simulator - a configfs-based GPIO testing
 	  driver.
 
+config GPIO_CONSUMER
+	tristate "GPIO Consumer Testing Module"
+	select CONFIGFS_FS
+	help
+	  This enables the configurable, configfs-based virtual GPIO consumer
+	  testing driver.
+
 endmenu
 
 endif
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index c3ac51d47aa9..268e8f65f3c8 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -46,6 +46,7 @@  obj-$(CONFIG_GPIO_BT8XX)		+= gpio-bt8xx.o
 obj-$(CONFIG_GPIO_CADENCE)		+= gpio-cadence.o
 obj-$(CONFIG_GPIO_CLPS711X)		+= gpio-clps711x.o
 obj-$(CONFIG_GPIO_SNPS_CREG)		+= gpio-creg-snps.o
+obj-$(CONFIG_GPIO_CONSUMER)		+= gpio-consumer.o
 obj-$(CONFIG_GPIO_CRYSTAL_COVE)		+= gpio-crystalcove.o
 obj-$(CONFIG_GPIO_CS5535)		+= gpio-cs5535.o
 obj-$(CONFIG_GPIO_DA9052)		+= gpio-da9052.o
diff --git a/drivers/gpio/gpio-consumer.c b/drivers/gpio/gpio-consumer.c
new file mode 100644
index 000000000000..fc6657e1af91
--- /dev/null
+++ b/drivers/gpio/gpio-consumer.c
@@ -0,0 +1,1004 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Configurable virtual GPIO consumer module.
+ *
+ * Copyright (C) 2023 Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/completion.h>
+#include <linux/configfs.h>
+#include <linux/device.h>
+#include <linux/gpio/consumer.h>
+#include <linux/gpio/machine.h>
+#include <linux/idr.h>
+#include <linux/interrupt.h>
+#include <linux/jiffies.h>
+#include <linux/kernel.h>
+#include <linux/limits.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/notifier.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/printk.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/timer.h>
+
+#include "gpiolib.h"
+
+#define GPIO_CONSUMER_MAX_PROPS 3
+
+enum gpio_consumer_function {
+	GPIO_CONSUMER_FUNCTION_ACTIVE = 0,
+	GPIO_CONSUMER_FUNCTION_TOGGLE,
+	GPIO_CONSUMER_FUNCTION_MONITOR,
+	__GPIO_CONSUMER_FUNCTION_LAST,
+};
+
+static const char *const gpio_consumer_function_strings[] = {
+	[GPIO_CONSUMER_FUNCTION_ACTIVE] = "active",
+	[GPIO_CONSUMER_FUNCTION_TOGGLE] = "toggle",
+	[GPIO_CONSUMER_FUNCTION_MONITOR] = "monitor",
+	NULL
+};
+
+struct gpio_consumer_irq_data {
+	struct device *dev;
+	struct gpio_desc *desc;
+};
+
+struct gpio_consumer_timer_data {
+	struct timer_list timer;
+	struct gpio_desc *desc;
+	int val;
+};
+
+static struct gpio_consumer_timer_data *to_timer_data(struct timer_list *timer)
+{
+	return container_of(timer, struct gpio_consumer_timer_data, timer);
+}
+
+static DEFINE_IDA(gpio_consumer_ida);
+
+static irqreturn_t gpio_consumer_on_irq(int irq, void *data)
+{
+	struct gpio_consumer_irq_data *irq_data = data;
+	struct gpio_desc *desc = irq_data->desc;
+	struct gpio_device *gdev = desc->gdev;
+	struct device *dev = irq_data->dev;
+	int val;
+
+	val = gpiod_get_value_cansleep(desc);
+	if (val < 0) {
+		dev_err(dev, "failed to read GPIO value: %d\n", val);
+		return IRQ_HANDLED;
+	}
+
+	dev_info(dev, "interrupt triggered on line %u of %s, new value: %d\n",
+		 gpio_chip_hwgpio(desc), dev_name(&gdev->dev), val);
+
+	return IRQ_HANDLED;
+}
+
+static void gpio_consumer_on_timer(struct timer_list *timer)
+{
+	struct gpio_consumer_timer_data *timer_data = to_timer_data(timer);
+
+	timer_data->val = timer_data->val == 0 ? 1 : 0;
+	gpiod_set_value_cansleep(timer_data->desc, timer_data->val);
+	mod_timer(&timer_data->timer, jiffies + msecs_to_jiffies(1000));
+}
+
+static void gpio_consumer_del_timer(void *data)
+{
+	struct timer_list *timer = data;
+
+	del_timer(timer);
+}
+
+static int gpio_consumer_probe(struct platform_device *pdev)
+{
+	struct gpio_consumer_timer_data *timer_data;
+	struct gpio_consumer_irq_data *irq_data;
+	enum gpio_consumer_function function;
+	const char *function_prop, **lines;
+	struct device *dev = &pdev->dev;
+	struct gpio_desc *desc;
+	enum gpiod_flags flags;
+	int ret, num_lines, i;
+
+	ret = device_property_read_string(dev, "gpio-virtual-consumer,function",
+					  &function_prop);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "Failed to read the consumer GPIO function\n");
+
+	ret = match_string(gpio_consumer_function_strings, -1, function_prop);
+	if (ret < 0)
+		return dev_err_probe(dev, -EINVAL,
+				     "Invalid consumer function: '%s'\n",
+				     function_prop);
+
+	function = ret;
+	num_lines = device_property_string_array_count(dev,
+					"gpio-virtual-consumer,lines");
+	if (num_lines < 0)
+		return dev_err_probe(dev, num_lines,
+				     "List of GPIO lines to request not found\n");
+
+	lines = devm_kcalloc(dev, num_lines, sizeof(*lines), GFP_KERNEL);
+	if (!lines)
+		return -ENOMEM;
+
+	ret = device_property_read_string_array(dev,
+						"gpio-virtual-consumer,lines",
+						lines, num_lines);
+	if (ret < 0)
+		return dev_err_probe(dev, ret,
+				     "Failed to read GPIO line names\n");
+
+	flags = function == GPIO_CONSUMER_FUNCTION_MONITOR ?
+					GPIOD_IN : GPIOD_OUT_HIGH;
+	for (i = 0; i < num_lines; i++) {
+		desc = devm_gpiod_get(dev, lines[i], flags);
+		if (IS_ERR(desc))
+			return dev_err_probe(dev, PTR_ERR(desc),
+					     "Failed to get GPIO '%s'\n",
+					     lines[i]);
+
+		if (function == GPIO_CONSUMER_FUNCTION_MONITOR) {
+			irq_data = devm_kzalloc(dev, sizeof(*irq_data),
+						GFP_KERNEL);
+			if (!irq_data)
+				return -ENOMEM;
+
+			irq_data->dev = dev;
+			irq_data->desc = desc;
+
+			ret = devm_request_threaded_irq(dev, gpiod_to_irq(desc),
+							NULL,
+							gpio_consumer_on_irq,
+							IRQF_TRIGGER_FALLING |
+							IRQF_TRIGGER_RISING |
+							IRQF_ONESHOT,
+							lines[i], irq_data);
+			if (ret)
+				return dev_err_probe(dev, ret,
+						"Failed to request GPIO line interrupt\n");
+		} else if (function == GPIO_CONSUMER_FUNCTION_TOGGLE) {
+			timer_data = devm_kzalloc(dev, sizeof(*timer_data),
+						  GFP_KERNEL);
+			if (!timer_data)
+				return -ENOMEM;
+
+			timer_data->desc = desc;
+			timer_data->val = 1;
+
+			timer_setup(&timer_data->timer,
+				    gpio_consumer_on_timer, 0);
+			mod_timer(&timer_data->timer,
+				  jiffies + msecs_to_jiffies(1000));
+
+			ret = devm_add_action_or_reset(dev,
+						       gpio_consumer_del_timer,
+						       &timer_data->timer);
+			if (ret)
+				return ret;
+		}
+	}
+
+	return 0;
+}
+
+static const struct of_device_id gpio_consumer_of_match[] = {
+	{ .compatible = "gpio-virtual-consumer" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, gpio_consumer_of_match);
+
+static struct platform_driver gpio_consumer_driver = {
+	.driver = {
+		.name = "gpio-virtual-consumer",
+		.of_match_table = gpio_consumer_of_match,
+	},
+	.probe = gpio_consumer_probe,
+};
+
+struct gpio_consumer_device {
+	struct config_group group;
+
+	struct platform_device *pdev;
+	int id;
+	struct mutex lock;
+
+	struct notifier_block bus_notifier;
+	struct completion probe_completion;
+	bool driver_bound;
+
+	struct gpiod_lookup_table *lookup_table;
+	enum gpio_consumer_function function;
+
+	struct list_head lookup_list;
+};
+
+static int gpio_consumer_bus_notifier_call(struct notifier_block *nb,
+					   unsigned long action, void *data)
+{
+	struct gpio_consumer_device *consumer;
+	struct device *dev = data;
+	char devname[32];
+
+	consumer = container_of(nb, struct gpio_consumer_device, bus_notifier);
+	snprintf(devname, sizeof(devname), "gpio-virtual-consumer.%d",
+		 consumer->id);
+
+	if (strcmp(dev_name(dev), devname) == 0) {
+		switch (action) {
+		case BUS_NOTIFY_BOUND_DRIVER:
+			consumer->driver_bound = true;
+			break;
+		case BUS_NOTIFY_DRIVER_NOT_BOUND:
+			consumer->driver_bound = false;
+			break;
+		default:
+			return NOTIFY_DONE;
+		}
+
+		complete(&consumer->probe_completion);
+		return NOTIFY_OK;
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct gpio_consumer_device *
+to_gpio_consumer_device(struct config_item *item)
+{
+	struct config_group *group = to_config_group(item);
+
+	return container_of(group, struct gpio_consumer_device, group);
+}
+
+static bool
+gpio_consumer_device_is_live_unlocked(struct gpio_consumer_device *dev)
+{
+	return !!dev->pdev;
+}
+
+struct gpio_consumer_lookup {
+	struct config_group group;
+
+	struct gpio_consumer_device *parent;
+	struct list_head siblings;
+
+	char *con_id;
+	char *key;
+	/* Can be negative to indicate lookup by name. */
+	int offset;
+
+	enum gpio_lookup_flags flags;
+};
+
+static struct gpio_consumer_lookup *
+to_gpio_consumer_lookup(struct config_item *item)
+{
+	struct config_group *group = to_config_group(item);
+
+	return container_of(group, struct gpio_consumer_lookup, group);
+}
+
+static ssize_t
+gpio_consumer_lookup_config_key_show(struct config_item *item, char *page)
+{
+	struct gpio_consumer_lookup *lookup = to_gpio_consumer_lookup(item);
+	struct gpio_consumer_device *dev = lookup->parent;
+	int ret;
+
+	mutex_lock(&dev->lock);
+	ret = sprintf(page, "%s\n", lookup->key);
+	mutex_unlock(&dev->lock);
+
+	return ret;
+}
+
+static ssize_t
+gpio_consumer_lookup_config_key_store(struct config_item *item,
+				      const char *page, size_t count)
+{
+	struct gpio_consumer_lookup *lookup = to_gpio_consumer_lookup(item);
+	struct gpio_consumer_device *dev = lookup->parent;
+	char *key, *stripped;
+
+	key = kstrndup(page, count, GFP_KERNEL);
+	if (!key)
+		return -ENOMEM;
+
+	stripped = strstrip(key);
+	memmove(key, stripped, strlen(stripped) + 1);
+
+	mutex_lock(&dev->lock);
+
+	if (gpio_consumer_device_is_live_unlocked(dev)) {
+		mutex_unlock(&dev->lock);
+		kfree(key);
+		return -EBUSY;
+	}
+
+	kfree(lookup->key);
+	lookup->key = key;
+
+	mutex_unlock(&dev->lock);
+
+	return count;
+}
+
+CONFIGFS_ATTR(gpio_consumer_lookup_config_, key);
+
+static ssize_t
+gpio_consumer_lookup_config_offset_show(struct config_item *item, char *page)
+{
+	struct gpio_consumer_lookup *lookup = to_gpio_consumer_lookup(item);
+	struct gpio_consumer_device *dev = lookup->parent;
+	unsigned int offset;
+
+	mutex_lock(&dev->lock);
+	offset = lookup->offset;
+	mutex_unlock(&dev->lock);
+
+	return sprintf(page, "%d\n", offset);
+}
+
+static ssize_t
+gpio_consumer_lookup_config_offset_store(struct config_item *item,
+					 const char *page, size_t count)
+{
+	struct gpio_consumer_lookup *lookup = to_gpio_consumer_lookup(item);
+	struct gpio_consumer_device *dev = lookup->parent;
+	int offset, ret;
+
+	ret = kstrtoint(page, 0, &offset);
+	if (ret)
+		return ret;
+
+	/* Use -1 to indicate lookup by name. */
+	if (offset > (U16_MAX - 1))
+		return -EINVAL;
+
+	mutex_lock(&dev->lock);
+
+	if (gpio_consumer_device_is_live_unlocked(dev)) {
+		mutex_unlock(&dev->lock);
+		return -EBUSY;
+	}
+
+	lookup->offset = offset;
+
+	mutex_unlock(&dev->lock);
+
+	return count;
+}
+
+CONFIGFS_ATTR(gpio_consumer_lookup_config_, offset);
+
+static enum gpio_lookup_flags
+gpio_consumer_lookup_get_flags(struct config_item *item)
+{
+	struct gpio_consumer_lookup *lookup = to_gpio_consumer_lookup(item);
+	struct gpio_consumer_device *dev = lookup->parent;
+	enum gpio_lookup_flags flags;
+
+	mutex_lock(&dev->lock);
+	flags = lookup->flags;
+	mutex_unlock(&dev->lock);
+
+	return flags;
+}
+
+static ssize_t
+gpio_consumer_lookup_config_drive_show(struct config_item *item, char *page)
+{
+	enum gpio_lookup_flags flags;
+	const char *repr;
+
+	flags = gpio_consumer_lookup_get_flags(item);
+
+	if (flags & GPIO_OPEN_DRAIN)
+		repr = "open-drain";
+	else if (flags & GPIO_OPEN_SOURCE)
+		repr = "open-source";
+	else
+		repr = "push-pull";
+
+	return sprintf(page, "%s\n", repr);
+}
+
+static ssize_t
+gpio_consumer_lookup_config_drive_store(struct config_item *item,
+					const char *page, size_t count)
+{
+	struct gpio_consumer_lookup *lookup = to_gpio_consumer_lookup(item);
+	struct gpio_consumer_device *dev = lookup->parent;
+
+	mutex_lock(&dev->lock);
+
+	if (gpio_consumer_device_is_live_unlocked(dev)) {
+		mutex_unlock(&dev->lock);
+		return -EBUSY;
+	}
+
+	if (sysfs_streq(page, "push-pull")) {
+		lookup->flags &= ~(GPIO_OPEN_DRAIN | GPIO_OPEN_SOURCE);
+	} else if (sysfs_streq(page, "open-drain")) {
+		lookup->flags &= ~GPIO_OPEN_SOURCE;
+		lookup->flags |= GPIO_OPEN_DRAIN;
+	} else if (sysfs_streq(page, "open-source")) {
+		lookup->flags &= ~GPIO_OPEN_DRAIN;
+		lookup->flags |= GPIO_OPEN_SOURCE;
+	} else {
+		count = -EINVAL;
+	}
+
+	mutex_unlock(&dev->lock);
+
+	return count;
+}
+
+CONFIGFS_ATTR(gpio_consumer_lookup_config_, drive);
+
+static ssize_t
+gpio_consumer_lookup_config_pull_show(struct config_item *item, char *page)
+{
+	enum gpio_lookup_flags flags;
+	const char *repr;
+
+	flags = gpio_consumer_lookup_get_flags(item);
+
+	if (flags & GPIO_PULL_UP)
+		repr = "pull-up";
+	else if (flags & GPIO_PULL_DOWN)
+		repr = "pull-down";
+	else if (flags & GPIO_PULL_DISABLE)
+		repr = "pull-disabled";
+	else
+		repr = "as-is";
+
+	return sprintf(page, "%s\n", repr);
+}
+
+static ssize_t
+gpio_consumer_lookup_config_pull_store(struct config_item *item,
+				       const char *page, size_t count)
+{
+	struct gpio_consumer_lookup *lookup = to_gpio_consumer_lookup(item);
+	struct gpio_consumer_device *dev = lookup->parent;
+
+	mutex_lock(&dev->lock);
+
+	if (gpio_consumer_device_is_live_unlocked(dev)) {
+		mutex_unlock(&dev->lock);
+		return -EBUSY;
+	}
+
+	if (sysfs_streq(page, "pull-up")) {
+		lookup->flags &= ~(GPIO_PULL_DOWN | GPIO_PULL_DISABLE);
+		lookup->flags |= GPIO_PULL_UP;
+	} else if (sysfs_streq(page, "pull-down")) {
+		lookup->flags &= ~(GPIO_PULL_UP | GPIO_PULL_DISABLE);
+		lookup->flags |= GPIO_PULL_DOWN;
+	} else if (sysfs_streq(page, "pull-disabled")) {
+		lookup->flags &= ~(GPIO_PULL_UP | GPIO_PULL_DOWN);
+		lookup->flags |= GPIO_PULL_DISABLE;
+	} else if (sysfs_streq(page, "as-is")) {
+		lookup->flags &= ~(GPIO_PULL_UP | GPIO_PULL_DOWN |
+				   GPIO_PULL_DISABLE);
+	} else {
+		count = -EINVAL;
+	}
+
+	mutex_unlock(&dev->lock);
+
+	return count;
+}
+
+CONFIGFS_ATTR(gpio_consumer_lookup_config_, pull);
+
+static ssize_t
+gpio_consumer_lookup_config_active_low_show(struct config_item *item,
+					    char *page)
+{
+	enum gpio_lookup_flags flags;
+
+	flags = gpio_consumer_lookup_get_flags(item);
+
+	return sprintf(page, "%s\n", flags & GPIO_ACTIVE_LOW ? "1" : "0");
+}
+
+static ssize_t
+gpio_consumer_lookup_config_active_low_store(struct config_item *item,
+					     const char *page, size_t count)
+{
+	struct gpio_consumer_lookup *lookup = to_gpio_consumer_lookup(item);
+	struct gpio_consumer_device *dev = lookup->parent;
+	bool active_low;
+	int ret;
+
+	ret = kstrtobool(page, &active_low);
+	if (ret)
+		return ret;
+
+	mutex_lock(&dev->lock);
+
+	if (gpio_consumer_device_is_live_unlocked(dev)) {
+		mutex_unlock(&dev->lock);
+		return -EBUSY;
+	}
+
+	if (active_low)
+		lookup->flags |= GPIO_ACTIVE_LOW;
+	else
+		lookup->flags &= ~GPIO_ACTIVE_LOW;
+
+	mutex_unlock(&dev->lock);
+
+	return count;
+}
+
+CONFIGFS_ATTR(gpio_consumer_lookup_config_, active_low);
+
+static ssize_t
+gpio_consumer_lookup_config_transitory_show(struct config_item *item,
+					    char *page)
+{
+	enum gpio_lookup_flags flags;
+
+	flags = gpio_consumer_lookup_get_flags(item);
+
+	return sprintf(page, "%s\n", flags & GPIO_TRANSITORY ? "1" : "0");
+}
+
+static ssize_t
+gpio_consumer_lookup_config_transitory_store(struct config_item *item,
+					     const char *page, size_t count)
+{
+	struct gpio_consumer_lookup *lookup = to_gpio_consumer_lookup(item);
+	struct gpio_consumer_device *dev = lookup->parent;
+	bool transitory;
+	int ret;
+
+	ret = kstrtobool(page, &transitory);
+	if (ret)
+		return ret;
+
+	mutex_lock(&dev->lock);
+
+	if (gpio_consumer_device_is_live_unlocked(dev)) {
+		mutex_unlock(&dev->lock);
+		return -EBUSY;
+	}
+
+	if (transitory)
+		lookup->flags |= GPIO_TRANSITORY;
+	else
+		lookup->flags &= ~GPIO_TRANSITORY;
+
+	mutex_unlock(&dev->lock);
+
+	return count;
+}
+
+CONFIGFS_ATTR(gpio_consumer_lookup_config_, transitory);
+
+static struct configfs_attribute *gpio_consumer_lookup_config_attrs[] = {
+	&gpio_consumer_lookup_config_attr_key,
+	&gpio_consumer_lookup_config_attr_offset,
+	&gpio_consumer_lookup_config_attr_drive,
+	&gpio_consumer_lookup_config_attr_pull,
+	&gpio_consumer_lookup_config_attr_active_low,
+	&gpio_consumer_lookup_config_attr_transitory,
+	NULL
+};
+
+static ssize_t gpio_consumer_device_config_live_show(struct config_item *item,
+						     char *page)
+{
+	struct gpio_consumer_device *dev = to_gpio_consumer_device(item);
+	bool live;
+
+	mutex_lock(&dev->lock);
+	live = gpio_consumer_device_is_live_unlocked(dev);
+	mutex_unlock(&dev->lock);
+
+	return sprintf(page, "%c\n", live ? '1' : '0');
+}
+
+static int
+gpio_consumer_make_lookup_table_unlocked(struct gpio_consumer_device *dev)
+{
+	struct gpio_consumer_lookup *lookup;
+	struct gpiod_lookup_table *table;
+	struct gpiod_lookup *curr;
+	size_t num_entries;
+	unsigned int i = 0;
+
+	num_entries = list_count_nodes(&dev->lookup_list);
+	table = kzalloc(sizeof(*table) + num_entries * sizeof(*table->table),
+			GFP_KERNEL);
+	if (!table)
+		return -ENOMEM;
+
+	table->dev_id = kasprintf(GFP_KERNEL, "gpio-virtual-consumer.%d",
+				  dev->id);
+	if (!table->dev_id) {
+		kfree(table);
+		return -ENOMEM;
+	}
+
+	list_for_each_entry(lookup, &dev->lookup_list, siblings) {
+		curr = &table->table[i];
+
+		curr->key = lookup->key;
+		curr->chip_hwnum = lookup->offset < 0 ?
+					U16_MAX : lookup->offset;
+		curr->con_id = lookup->con_id;
+		curr->flags = lookup->flags;
+	}
+
+	gpiod_add_lookup_table(table);
+	dev->lookup_table = table;
+
+	return 0;
+}
+
+static struct fwnode_handle *
+gpio_consumer_make_device_swnode(struct gpio_consumer_device *dev)
+{
+	struct property_entry properties[GPIO_CONSUMER_MAX_PROPS];
+	struct gpio_consumer_lookup *lookup;
+	struct fwnode_handle *swnode;
+	int prop_idx = 0, i = 0;
+	size_t num_lookups;
+	char **lines;
+
+	memset(properties, 0, sizeof(properties));
+
+	properties[prop_idx++] = PROPERTY_ENTRY_STRING(
+			"gpio-virtual-consumer,function",
+			gpio_consumer_function_strings[dev->function]);
+
+	num_lookups = list_count_nodes(&dev->lookup_list);
+	lines = kcalloc(num_lookups + 1, sizeof(*lines), GFP_KERNEL);
+	if (!lines)
+		return ERR_PTR(-ENOMEM);
+
+	list_for_each_entry(lookup, &dev->lookup_list, siblings)
+		lines[i++] = lookup->con_id;
+
+	properties[prop_idx++] = PROPERTY_ENTRY_STRING_ARRAY_LEN(
+		"gpio-virtual-consumer,lines", lines, num_lookups);
+
+	swnode = fwnode_create_software_node(properties, NULL);
+	kfree(lines);
+	return swnode;
+}
+
+static int
+gpio_consumer_device_activate_unlocked(struct gpio_consumer_device *dev)
+{
+	struct platform_device_info pdevinfo;
+	struct fwnode_handle *swnode;
+	struct platform_device *pdev;
+	int ret;
+
+	if (list_empty(&dev->lookup_list))
+		return -ENODATA;
+
+	swnode = gpio_consumer_make_device_swnode(dev);
+	if (IS_ERR(swnode))
+		return PTR_ERR(swnode);
+
+	memset(&pdevinfo, 0, sizeof(pdevinfo));
+	pdevinfo.name = "gpio-virtual-consumer";
+	pdevinfo.id = dev->id;
+	pdevinfo.fwnode = swnode;
+
+	ret = gpio_consumer_make_lookup_table_unlocked(dev);
+	if (ret) {
+		fwnode_remove_software_node(swnode);
+		return ret;
+	}
+
+	reinit_completion(&dev->probe_completion);
+	dev->driver_bound = false;
+	bus_register_notifier(&platform_bus_type, &dev->bus_notifier);
+
+	pdev = platform_device_register_full(&pdevinfo);
+	if (IS_ERR(pdev)) {
+		bus_unregister_notifier(&platform_bus_type, &dev->bus_notifier);
+		fwnode_remove_software_node(swnode);
+		return PTR_ERR(pdev);
+	}
+
+	wait_for_completion(&dev->probe_completion);
+	bus_unregister_notifier(&platform_bus_type, &dev->bus_notifier);
+
+	if (!dev->driver_bound) {
+		platform_device_unregister(pdev);
+		fwnode_remove_software_node(swnode);
+		return -ENXIO;
+	}
+
+	dev->pdev = pdev;
+
+	return 0;
+}
+
+static void
+gpio_consumer_device_deactivate_unlocked(struct gpio_consumer_device *dev)
+{
+	struct fwnode_handle *swnode;
+
+	swnode = dev_fwnode(&dev->pdev->dev);
+	platform_device_unregister(dev->pdev);
+	fwnode_remove_software_node(swnode);
+	dev->pdev = NULL;
+	kfree(dev->lookup_table);
+}
+
+static ssize_t
+gpio_consumer_device_config_live_store(struct config_item *item,
+				       const char *page, size_t count)
+{
+	struct gpio_consumer_device *dev = to_gpio_consumer_device(item);
+	bool live;
+	int ret;
+
+	ret = kstrtobool(page, &live);
+	if (ret)
+		return ret;
+
+	mutex_lock(&dev->lock);
+
+	if ((!live && !gpio_consumer_device_is_live_unlocked(dev)) ||
+	    (live && gpio_consumer_device_is_live_unlocked(dev)))
+		ret = -EPERM;
+	else if (live)
+		ret = gpio_consumer_device_activate_unlocked(dev);
+	else
+		gpio_consumer_device_deactivate_unlocked(dev);
+
+	mutex_unlock(&dev->lock);
+
+	return ret ?: count;
+}
+
+CONFIGFS_ATTR(gpio_consumer_device_config_, live);
+
+static ssize_t
+gpio_consumer_device_config_function_show(struct config_item *item, char *page)
+{
+	struct gpio_consumer_device *dev = to_gpio_consumer_device(item);
+	enum gpio_consumer_function function;
+	const char *repr;
+
+	mutex_lock(&dev->lock);
+	function = dev->function;
+	mutex_unlock(&dev->lock);
+
+	repr = gpio_consumer_function_strings[function];
+
+	return sprintf(page, "%s\n", repr);
+}
+
+static ssize_t
+gpio_consumer_device_config_function_store(struct config_item *item,
+					   const char *page, size_t count)
+{
+	struct gpio_consumer_device *dev = to_gpio_consumer_device(item);
+	int ret;
+
+	ret = sysfs_match_string(gpio_consumer_function_strings, page);
+	if (ret < 0)
+		return -EINVAL;
+
+	mutex_lock(&dev->lock);
+
+	if (gpio_consumer_device_is_live_unlocked(dev)) {
+		mutex_unlock(&dev->lock);
+		return -EBUSY;
+	}
+
+	dev->function = ret;
+
+	mutex_unlock(&dev->lock);
+
+	return count;
+}
+
+CONFIGFS_ATTR(gpio_consumer_device_config_, function);
+
+static struct configfs_attribute *gpio_consumer_device_config_attrs[] = {
+	&gpio_consumer_device_config_attr_live,
+	&gpio_consumer_device_config_attr_function,
+	NULL
+};
+
+static void gpio_consumer_lookup_config_group_release(struct config_item *item)
+{
+	struct gpio_consumer_lookup *lookup = to_gpio_consumer_lookup(item);
+	struct gpio_consumer_device *dev = lookup->parent;
+
+	mutex_lock(&dev->lock);
+	list_del(&lookup->siblings);
+	mutex_unlock(&dev->lock);
+
+	kfree(lookup->con_id);
+	kfree(lookup->key);
+	kfree(lookup);
+}
+
+static struct configfs_item_operations gpio_consumer_lookup_config_item_ops = {
+	.release	= gpio_consumer_lookup_config_group_release,
+};
+
+static const struct config_item_type gpio_consumer_lookup_config_group_type = {
+	.ct_item_ops	= &gpio_consumer_lookup_config_item_ops,
+	.ct_attrs	= gpio_consumer_lookup_config_attrs,
+	.ct_owner	= THIS_MODULE,
+};
+
+static struct config_group *
+gpio_consumer_device_make_lookup_group(struct config_group *group,
+				       const char *name)
+{
+	struct gpio_consumer_device *dev =
+			to_gpio_consumer_device(&group->cg_item);
+	struct gpio_consumer_lookup *lookup;
+
+	mutex_lock(&dev->lock);
+
+	if (gpio_consumer_device_is_live_unlocked(dev)) {
+		mutex_unlock(&dev->lock);
+		return ERR_PTR(-EBUSY);
+	}
+
+	lookup = kzalloc(sizeof(*lookup), GFP_KERNEL);
+	if (!lookup) {
+		mutex_unlock(&dev->lock);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	lookup->con_id = kstrdup(name, GFP_KERNEL);
+	if (!lookup->con_id) {
+		mutex_unlock(&dev->lock);
+		kfree(lookup);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	config_group_init_type_name(&lookup->group, name,
+				    &gpio_consumer_lookup_config_group_type);
+	lookup->flags = GPIO_LOOKUP_FLAGS_DEFAULT;
+	lookup->parent = dev;
+	list_add_tail(&lookup->siblings, &dev->lookup_list);
+
+	mutex_unlock(&dev->lock);
+
+	return &lookup->group;
+}
+
+static void gpio_consumer_device_config_group_release(struct config_item *item)
+{
+	struct gpio_consumer_device *dev = to_gpio_consumer_device(item);
+
+	mutex_lock(&dev->lock);
+	if (gpio_consumer_device_is_live_unlocked(dev))
+		gpio_consumer_device_deactivate_unlocked(dev);
+	mutex_unlock(&dev->lock);
+
+	mutex_destroy(&dev->lock);
+	ida_free(&gpio_consumer_ida, dev->id);
+	kfree(dev);
+}
+
+static struct configfs_item_operations gpio_consumer_device_config_item_ops = {
+	.release	= gpio_consumer_device_config_group_release,
+};
+
+static struct configfs_group_operations gpio_consumer_device_config_group_ops = {
+	.make_group	= gpio_consumer_device_make_lookup_group,
+};
+
+static const struct config_item_type gpio_consumer_device_config_group_type = {
+	.ct_group_ops	= &gpio_consumer_device_config_group_ops,
+	.ct_item_ops	= &gpio_consumer_device_config_item_ops,
+	.ct_attrs	= gpio_consumer_device_config_attrs,
+	.ct_owner	= THIS_MODULE,
+};
+
+static struct config_group *
+gpio_consumer_config_make_device_group(struct config_group *group,
+				       const char *name)
+{
+	struct gpio_consumer_device *dev;
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return ERR_PTR(-ENOMEM);
+
+	dev->id = ida_alloc(&gpio_consumer_ida, GFP_KERNEL);
+	if (dev->id < 0) {
+		kfree(dev);
+		return ERR_PTR(dev->id);
+	}
+
+	config_group_init_type_name(&dev->group, name,
+				    &gpio_consumer_device_config_group_type);
+	mutex_init(&dev->lock);
+	INIT_LIST_HEAD(&dev->lookup_list);
+	dev->bus_notifier.notifier_call = gpio_consumer_bus_notifier_call;
+	dev->function = GPIO_CONSUMER_FUNCTION_ACTIVE;
+	init_completion(&dev->probe_completion);
+
+	return &dev->group;
+}
+
+static struct configfs_group_operations gpio_consumer_config_group_ops = {
+	.make_group	= gpio_consumer_config_make_device_group,
+};
+
+static const struct config_item_type gpio_consumer_config_type = {
+	.ct_group_ops	= &gpio_consumer_config_group_ops,
+	.ct_owner	= THIS_MODULE,
+};
+
+static struct configfs_subsystem gpio_consumer_config_subsys = {
+	.su_group = {
+		.cg_item = {
+			.ci_namebuf	= "gpio-consumer",
+			.ci_type	= &gpio_consumer_config_type,
+		},
+	},
+};
+
+static int __init gpio_consumer_init(void)
+{
+	int ret;
+
+	ret = platform_driver_register(&gpio_consumer_driver);
+	if (ret) {
+		pr_err("Failed to register the gpio-consumer platform driver: %d\n",
+		       ret);
+		return ret;
+	}
+
+	config_group_init(&gpio_consumer_config_subsys.su_group);
+	mutex_init(&gpio_consumer_config_subsys.su_mutex);
+	ret = configfs_register_subsystem(&gpio_consumer_config_subsys);
+	if (ret) {
+		pr_err("Failed to register the '%s' configfs subsystem: %d\n",
+		       gpio_consumer_config_subsys.su_group.cg_item.ci_namebuf,
+		       ret);
+		mutex_destroy(&gpio_consumer_config_subsys.su_mutex);
+		platform_driver_unregister(&gpio_consumer_driver);
+		return ret;
+	}
+
+	return 0;
+}
+module_init(gpio_consumer_init);
+
+static void __exit gpio_consumer_exit(void)
+{
+	configfs_unregister_subsystem(&gpio_consumer_config_subsys);
+	mutex_destroy(&gpio_consumer_config_subsys.su_mutex);
+	platform_driver_unregister(&gpio_consumer_driver);
+}
+module_exit(gpio_consumer_exit);
+
+MODULE_AUTHOR("Bartosz Golaszewski <bartosz.golaszewski@linaro.org>");
+MODULE_DESCRIPTION("Virtual GPIO consumer module");
+MODULE_LICENSE("GPL");