path: root/drivers/gpio/gpio-sim.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * GPIO testing driver based on configfs.
 *
 * Copyright (C) 2021 Bartosz Golaszewski <brgl@bgdev.pl>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/bitmap.h>
#include <linux/cleanup.h>
#include <linux/completion.h>
#include <linux/configfs.h>
#include <linux/device.h>
#include <linux/gpio/driver.h>
#include <linux/gpio/machine.h>
#include <linux/idr.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/irq_sim.h>
#include <linux/list.h>
#include <linux/minmax.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/notifier.h>
#include <linux/platform_device.h>
#include <linux/property.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/string_helpers.h>
#include <linux/sysfs.h>

#include "gpiolib.h"

#define GPIO_SIM_NGPIO_MAX	1024
#define GPIO_SIM_PROP_MAX	4 /* Max 3 properties + sentinel. */
#define GPIO_SIM_NUM_ATTRS	3 /* value, pull and sentinel */

static DEFINE_IDA(gpio_sim_ida);

struct gpio_sim_chip {
	struct gpio_chip gc;
	unsigned long *direction_map;
	unsigned long *value_map;
	unsigned long *pull_map;
	struct irq_domain *irq_sim;
	struct mutex lock;
	const struct attribute_group **attr_groups;
};

struct gpio_sim_attribute {
	struct device_attribute dev_attr;
	unsigned int offset;
};

static struct gpio_sim_attribute *
to_gpio_sim_attr(struct device_attribute *dev_attr)
{
	return container_of(dev_attr, struct gpio_sim_attribute, dev_attr);
}

static int gpio_sim_apply_pull(struct gpio_sim_chip *chip,
			       unsigned int offset, int value)
{
	int irq, irq_type, ret;
	struct gpio_desc *desc;
	struct gpio_chip *gc;

	gc = &chip->gc;
	desc = &gc->gpiodev->descs[offset];

	guard(mutex)(&chip->lock);

	if (test_bit(FLAG_REQUESTED, &desc->flags) &&
	    !test_bit(FLAG_IS_OUT, &desc->flags)) {
		if (value == !!test_bit(offset, chip->value_map))
			goto set_pull;

		/*
		 * This is fine - it just means, nobody is listening
		 * for interrupts on this line, otherwise
		 * irq_create_mapping() would have been called from
		 * the to_irq() callback.
		 */
		irq = irq_find_mapping(chip->irq_sim, offset);
		if (!irq)
			goto set_value;

		irq_type = irq_get_trigger_type(irq);

		if ((value && (irq_type & IRQ_TYPE_EDGE_RISING)) ||
		    (!value && (irq_type & IRQ_TYPE_EDGE_FALLING))) {
			ret = irq_set_irqchip_state(irq, IRQCHIP_STATE_PENDING,
						    true);
			if (ret)
				goto set_pull;
		}
	}

set_value:
	/* Change the value unless we're actively driving the line. */
	if (!test_bit(FLAG_REQUESTED, &desc->flags) ||
	    !test_bit(FLAG_IS_OUT, &desc->flags))
		__assign_bit(offset, chip->value_map, value);

set_pull:
	__assign_bit(offset, chip->pull_map, value);
	return 0;
}

static int gpio_sim_get(struct gpio_chip *gc, unsigned int offset)
{
	struct gpio_sim_chip *chip = gpiochip_get_data(gc);

	guard(mutex)(&chip->lock);

	return !!test_bit(offset, chip->value_map);
}

static void gpio_sim_set(struct gpio_chip *gc, unsigned int offset, int value)
{
	struct gpio_sim_chip *chip = gpiochip_get_data(gc);

	scoped_guard(mutex, &chip->lock)
		__assign_bit(offset, chip->value_map, value);
}

static int gpio_sim_get_multiple(struct gpio_chip *gc,
				 unsigned long *mask, unsigned long *bits)
{
	struct gpio_sim_chip *chip = gpiochip_get_data(gc);

	scoped_guard(mutex, &chip->lock)
		bitmap_replace(bits, bits, chip->value_map, mask, gc->ngpio);

	return 0;
}

static void gpio_sim_set_multiple(struct gpio_chip *gc,
				  unsigned long *mask, unsigned long *bits)
{
	struct gpio_sim_chip *chip = gpiochip_get_data(gc);

	scoped_guard(mutex, &chip->lock)
		bitmap_replace(chip->value_map, chip->value_map, bits, mask,
			       gc->ngpio);
}

static int gpio_sim_direction_output(struct gpio_chip *gc,
				     unsigned int offset, int value)
{
	struct gpio_sim_chip *chip = gpiochip_get_data(gc);

	scoped_guard(mutex, &chip->lock) {
		__clear_bit(offset, chip->direction_map);
		__assign_bit(offset, chip->value_map, value);
	}

	return 0;
}

static int gpio_sim_direction_input(struct gpio_chip *gc, unsigned int offset)
{
	struct gpio_sim_chip *chip = gpiochip_get_data(gc);

	scoped_guard(mutex, &chip->lock)
		__set_bit(offset, chip->direction_map);

	return 0;
}

static int gpio_sim_get_direction(struct gpio_chip *gc, unsigned int offset)
{
	struct gpio_sim_chip *chip = gpiochip_get_data(gc);
	int direction;

	scoped_guard(mutex, &chip->lock)
		direction = !!test_bit(offset, chip->direction_map);

	return direction ? GPIO_LINE_DIRECTION_IN : GPIO_LINE_DIRECTION_OUT;
}

static int gpio_sim_set_config(struct gpio_chip *gc,
				  unsigned int offset, unsigned long config)
{
	struct gpio_sim_chip *chip = gpiochip_get_data(gc);

	switch (pinconf_to_config_param(config)) {
	case PIN_CONFIG_BIAS_PULL_UP:
		return gpio_sim_apply_pull(chip, offset, 1);
	case PIN_CONFIG_BIAS_PULL_DOWN:
		return gpio_sim_apply_pull(chip, offset, 0);
	default:
		break;
	}

	return -ENOTSUPP;
}

static int gpio_sim_to_irq(struct gpio_chip *gc, unsigned int offset)
{
	struct gpio_sim_chip *chip = gpiochip_get_data(gc);

	return irq_create_mapping(chip->irq_sim, offset);
}

static void gpio_sim_free(struct gpio_chip *gc, unsigned int offset)
{
	struct gpio_sim_chip *chip = gpiochip_get_data(gc);

	scoped_guard(mutex, &chip->lock)
		__assign_bit(offset, chip->value_map,
			     !!test_bit(offset, chip->pull_map));
}

static ssize_t gpio_sim_sysfs_val_show(struct device *dev,
				       struct device_attribute *attr, char *buf)
{
	struct gpio_sim_attribute *line_attr = to_gpio_sim_attr(attr);
	struct gpio_sim_chip *chip = dev_get_drvdata(dev);
	int val;

	scoped_guard(mutex, &chip->lock)
		val = !!test_bit(line_attr->offset, chip->value_map);

	return sysfs_emit(buf, "%d\n", val);
}

static ssize_t gpio_sim_sysfs_val_store(struct device *dev,
					struct device_attribute *attr,
					const char *buf, size_t count)
{
	/*
	 * Not assigning this function will result in write() returning -EIO
	 * which is confusing. Return -EPERM explicitly.
	 */
	return -EPERM;
}

static const char *const gpio_sim_sysfs_pull_strings[] = {
	[0]	= "pull-down",
	[1]	= "pull-up",
};

static ssize_t gpio_sim_sysfs_pull_show(struct device *dev,
					struct device_attribute *attr,
					char *buf)
{
	struct gpio_sim_attribute *line_attr = to_gpio_sim_attr(attr);
	struct gpio_sim_chip *chip = dev_get_drvdata(dev);
	int pull;

	scoped_guard(mutex, &chip->lock)
		pull = !!test_bit(line_attr->offset, chip->pull_map);

	return sysfs_emit(buf, "%s\n", gpio_sim_sysfs_pull_strings[pull]);
}

static ssize_t gpio_sim_sysfs_pull_store(struct device *dev,
					 struct device_attribute *attr,
					 const char *buf, size_t len)
{
	struct gpio_sim_attribute *line_attr = to_gpio_sim_attr(attr);
	struct gpio_sim_chip *chip = dev_get_drvdata(dev);
	int ret, pull;

	pull = sysfs_match_string(gpio_sim_sysfs_pull_strings, buf);
	if (pull < 0)
		return pull;

	ret = gpio_sim_apply_pull(chip, line_attr->offset, pull);
	if (ret)
		return ret;

	return len;
}

static void gpio_sim_mutex_destroy(void *data)
{
	struct mutex *lock = data;

	mutex_destroy(lock);
}

static void gpio_sim_dispose_mappings(void *data)
{
	struct gpio_sim_chip *chip = data;
	unsigned int i;

	for (i = 0; i < chip->gc.ngpio; i++)
		irq_dispose_mapping(irq_find_mapping(chip->irq_sim, i));
}

static void gpio_sim_sysfs_remove(void *data)
{
	struct gpio_sim_chip *chip = data;

	sysfs_remove_groups(&chip->gc.gpiodev->dev.kobj, chip->attr_groups);
}

static int gpio_sim_setup_sysfs(struct gpio_sim_chip *chip)
{
	struct device_attribute *val_dev_attr, *pull_dev_attr;
	struct gpio_sim_attribute *val_attr, *pull_attr;
	unsigned int num_lines = chip->gc.ngpio;
	struct device *dev = chip->gc.parent;
	struct attribute_group *attr_group;
	struct attribute **attrs;
	int i, ret;

	chip->attr_groups = devm_kcalloc(dev, sizeof(*chip->attr_groups),
					 num_lines + 1, GFP_KERNEL);
	if (!chip->attr_groups)
		return -ENOMEM;

	for (i = 0; i < num_lines; i++) {
		attr_group = devm_kzalloc(dev, sizeof(*attr_group), GFP_KERNEL);
		attrs = devm_kcalloc(dev, GPIO_SIM_NUM_ATTRS, sizeof