// SPDX-License-Identifier: GPL-2.0+
/*
 * GPIO Testing Device Driver
 *
 * Copyright (C) 2014  Kamlakant Patel <kamlakant.patel@broadcom.com>
 * Copyright (C) 2015-2016  Bamvor Jian Zhang <bamv2005@gmail.com>
 * Copyright (C) 2017 Bartosz Golaszewski <brgl@bgdev.pl>
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/gpio/driver.h>
#include <linux/gpio/consumer.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/irq_sim.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/property.h>

#include "gpiolib.h"

#define GPIO_MOCKUP_NAME        "gpio-mockup"
#define GPIO_MOCKUP_MAX_GC      10
/*
 * We're storing two values per chip: the GPIO base and the number
 * of GPIO lines.
 */
#define GPIO_MOCKUP_MAX_RANGES  (GPIO_MOCKUP_MAX_GC * 2)
/* Maximum of three properties + the sentinel. */
#define GPIO_MOCKUP_MAX_PROP    4

#define gpio_mockup_err(...)    pr_err(GPIO_MOCKUP_NAME ": " __VA_ARGS__)

enum {
        GPIO_MOCKUP_DIR_IN = 0,
        GPIO_MOCKUP_DIR_OUT = 1,
};

/*
 * struct gpio_pin_status - structure describing a GPIO status
 * @dir:       Configures direction of gpio as "in" or "out", 0=in, 1=out
 * @value:     Configures status of the gpio as 0(low) or 1(high)
 */
struct gpio_mockup_line_status {
        int dir;
        int value;
        int pull;
};

struct gpio_mockup_chip {
        struct gpio_chip gc;
        struct gpio_mockup_line_status *lines;
        struct irq_sim irqsim;
        struct dentry *dbg_dir;
        struct mutex lock;
};

struct gpio_mockup_dbgfs_private {
        struct gpio_mockup_chip *chip;
        struct gpio_desc *desc;
        unsigned int offset;
};

static int gpio_mockup_ranges[GPIO_MOCKUP_MAX_RANGES];
static int gpio_mockup_num_ranges;
module_param_array(gpio_mockup_ranges, int, &gpio_mockup_num_ranges, 0400);

static bool gpio_mockup_named_lines;
module_param_named(gpio_mockup_named_lines,
                   gpio_mockup_named_lines, bool, 0400);

static struct dentry *gpio_mockup_dbg_dir;

static int gpio_mockup_range_base(unsigned int index)
{
        return gpio_mockup_ranges[index * 2];
}

static int gpio_mockup_range_ngpio(unsigned int index)
{
        return gpio_mockup_ranges[index * 2 + 1];
}

static int __gpio_mockup_get(struct gpio_mockup_chip *chip,
                             unsigned int offset)
{
        return chip->lines[offset].value;
}

static int gpio_mockup_get(struct gpio_chip *gc, unsigned int offset)
{
        struct gpio_mockup_chip *chip = gpiochip_get_data(gc);
        int val;

        mutex_lock(&chip->lock);
        val = __gpio_mockup_get(chip, offset);
        mutex_unlock(&chip->lock);

        return val;
}

static int gpio_mockup_get_multiple(struct gpio_chip *gc,
                                    unsigned long *mask, unsigned long *bits)
{
        struct gpio_mockup_chip *chip = gpiochip_get_data(gc);
        unsigned int bit, val;

        mutex_lock(&chip->lock);
        for_each_set_bit(bit, mask, gc->ngpio) {
                val = __gpio_mockup_get(chip, bit);
                __assign_bit(bit, bits, val);
        }
        mutex_unlock(&chip->lock);

        return 0;
}

static void __gpio_mockup_set(struct gpio_mockup_chip *chip,
                              unsigned int offset, int value)
{
        chip->lines[offset].value = !!value;
}

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

        mutex_lock(&chip->lock);
        __gpio_mockup_set(chip, offset, value);
        mutex_unlock(&chip->lock);
}

static void gpio_mockup_set_multiple(struct gpio_chip *gc,
                                     unsigned long *mask, unsigned long *bits)
{
        struct gpio_mockup_chip *chip = gpiochip_get_data(gc);
        unsigned int bit;

        mutex_lock(&chip->lock);
        for_each_set_bit(bit, mask, gc->ngpio)
                __gpio_mockup_set(chip, bit, test_bit(bit, bits));
        mutex_unlock(&chip->lock);
}

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

        mutex_lock(&chip->lock);
        chip->lines[offset].dir = GPIO_MOCKUP_DIR_OUT;
        __gpio_mockup_set(chip, offset, value);
        mutex_unlock(&chip->lock);

        return 0;
}

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

        mutex_lock(&chip->lock);
        chip->lines[offset].dir = GPIO_MOCKUP_DIR_IN;
        mutex_unlock(&chip->lock);

        return 0;
}

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

        mutex_lock(&chip->lock);
        direction = !chip->lines[offset].dir;
        mutex_unlock(&chip->lock);

        return direction;
}

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

        return irq_sim_irqnum(&chip->irqsim, offset);
}

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

        __gpio_mockup_set(chip, offset, chip->lines[offset].pull);
}

static ssize_t gpio_mockup_debugfs_read(struct file *file,
                                        char __user *usr_buf,
                                        size_t size, loff_t *ppos)
{
        struct gpio_mockup_dbgfs_private *priv;
        struct gpio_mockup_chip *chip;
        struct seq_file *sfile;
        struct gpio_chip *gc;
        int val, cnt;
        char buf[3];

        if (*ppos != 0)
                return 0;

        sfile = file->private_data;
        priv = sfile->private;
        chip = priv->chip;
        gc = &chip->gc;

        val = gpio_mockup_get(gc, priv->offset);
        cnt = snprintf(buf, sizeof(buf), "%d\n", val);

        return simple_read_from_buffer(usr_buf, size, ppos, buf, cnt);
}

static ssize_t gpio_mockup_debugfs_write(struct file *file,
                                         const char __user *usr_buf,
                                         size_t size, loff_t *ppos)
{
        struct gpio_mockup_dbgfs_private *priv;
        int rv, val, curr, irq, irq_type;
        struct gpio_mockup_chip *chip;
        struct seq_file *sfile;
        struct gpio_desc *desc;
        struct gpio_chip *gc;
        struct irq_sim *sim;

        if (*ppos != 0)
                return -EINVAL;

        rv = kstrtoint_from_user(usr_buf, size, 0, &val);
        if (rv)
                return rv;
        if (val != 0 && val != 1)
                return -EINVAL;

        sfile = file->private_data;
        priv = sfile->private;
        chip = priv->chip;
        gc = &chip->gc;
        desc = &gc->gpiodev->descs[priv->offset];
        sim = &chip->irqsim;

        mutex_lock(&chip->lock);

        if (test_bit(FLAG_REQUESTED, &desc->flags) &&
            !test_bit(FLAG_IS_OUT, &desc->flags)) {
                curr = __gpio_mockup_get(chip, priv->offset);
                if (curr == val)
                        goto out;

                irq = irq_sim_irqnum(sim, priv->offset);
                irq_type = irq_get_trigger_type(irq);

                if ((val == 1 && (irq_type & IRQ_TYPE_EDGE_RISING)) ||
                    (val == 0 && (irq_type & IRQ_TYPE_EDGE_FALLING)))
                        irq_sim_fire(sim, priv->offset);
        }

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

out:
        chip->lines[priv->offset].pull = val;
        mutex_unlock(&chip->lock);

        return size;
}

static int gpio_mockup_debugfs_open(struct inode *inode, struct file *file)
{
        return single_open(file, NULL, inode->i_private);
}

/*
 * Each mockup chip is represented by a directory named after the chip's device
 * name under /sys/kernel/debug/gpio-mockup/. Each line is represented by
 * a file using the line's offset as the name under the chip's directory.
 *
 * Reading from the line's file yields the current *value*, writing to the
 * line's file changes the current *pull*. Default pull for mockup lines is
 * down.
 *
 * Examples:
 * - when a line pulled down is requested in output mode and driven high, its
 *   value will return to 0 once it's released
 * - when the line is requested in output mode and driven high, writing 0 to
 *   the corresponding debugfs file will change the pull to down but the
 *   reported value will still be 1 until the line is released
 * - line requested in input mode always reports the same value as its pull
 *   configuration
 * - when the line is requested in input mode and monitored for events, writing
 *   the same value to the debugfs file will be a noop, while writing the
 *   opposite value will generate a dummy interrupt with an appropriate edge
 */
static const struct file_operations gpio_mockup_debugfs_ops = {
        .owner = THIS_MODULE,
        .open = gpio_mockup_debugfs_open,
        .read = gpio_mockup_debugfs_read,
        .write = gpio_mockup_debugfs_write,
        .llseek = no_llseek,
        .release = single_release,
};

static void gpio_mockup_debugfs_setup(struct device *dev,
                                      struct gpio_mockup_chip *chip)
{
        struct gpio_mockup_dbgfs_private *priv;
        struct gpio_chip *gc;
        const char *devname;
        char *name;
        int i;

        gc = &chip->gc;
        devname = dev_name(&gc->gpiodev->dev);

        chip->dbg_dir = debugfs_create_dir(devname, gpio_mockup_dbg_dir);

        for (i = 0; i < gc->ngpio; i++) {
                name = devm_kasprintf(dev, GFP_KERNEL, "%d", i);
                if (!name)
                        return;

                priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
                if (!priv)
                        return;

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

                debugfs_create_file(name, 0200, chip->dbg_dir, priv,
                                    &gpio_mockup_debugfs_ops);
        }

        return;
}

static int gpio_mockup_name_lines(struct device *dev,
                                  struct gpio_mockup_chip *chip)
{
        struct gpio_chip *gc = &chip->gc;
        char **names;
        int i;

        names = devm_kcalloc(dev, gc->ngpio, sizeof(char *), GFP_KERNEL);
        if (!names)
                return -ENOMEM;

        for (i = 0; i < gc->ngpio; i++) {
                names[i] = devm_kasprintf(dev, GFP_KERNEL,
                                          "%s-%d", gc->label, i);
                if (!names[i])
                        return -ENOMEM;
        }

        gc->names = (const char *const *)names;

        return 0;
}

static int gpio_mockup_probe(struct platform_device *pdev)
{
        struct gpio_mockup_chip *chip;
        struct gpio_chip *gc;
        struct device *dev;
        const char *name;
        int rv, base;
        u16 ngpio;

        dev = &pdev->dev;

        rv = device_property_read_u32(dev, "gpio-base", &base);
        if (rv)
                base = -1;

        rv = device_property_read_u16(dev, "nr-gpios", &ngpio);
        if (rv)
                return rv;

        rv = device_property_read_string(dev, "chip-name", &name);
        if (rv)
                name = NULL;

        chip = devm_kzalloc(dev, sizeof(*chip), GFP_KERNEL);
        if (!chip)
                return -ENOMEM;

        if (!name) {
                name = devm_kasprintf(dev, GFP_KERNEL,
                                      "%s-%c", pdev->name, pdev->id + 'A');
                if (!name)
                        return -ENOMEM;
        }

        mutex_init(&chip->lock);

        gc = &chip->gc;
        gc->base = base;
        gc->ngpio = ngpio;
        gc->label = name;
        gc->owner = THIS_MODULE;
        gc->parent = dev;
        gc->get = gpio_mockup_get;
        gc->set = gpio_mockup_set;
        gc->get_multiple = gpio_mockup_get_multiple;
        gc->set_multiple = gpio_mockup_set_multiple;
        gc->direction_output = gpio_mockup_dirout;
        gc->direction_input = gpio_mockup_dirin;
        gc->get_direction = gpio_mockup_get_direction;
        gc->to_irq = gpio_mockup_to_irq;
        gc->free = gpio_mockup_free;

        chip->lines = devm_kcalloc(dev, gc->ngpio,
                                   sizeof(*chip->lines), GFP_KERNEL);
        if (!chip->lines)
                return -ENOMEM;

        if (device_property_read_bool(dev, "named-gpio-lines")) {
                rv = gpio_mockup_name_lines(dev, chip);
                if (rv)
                        return rv;
        }

        rv = devm_irq_sim_init(dev, &chip->irqsim, gc->ngpio);
        if (rv < 0)
                return rv;

        rv = devm_gpiochip_add_data(dev, &chip->gc, chip);
        if (rv)
                return rv;

        gpio_mockup_debugfs_setup(dev, chip);

        return 0;
}

static struct platform_driver gpio_mockup_driver = {
        .driver = {
                .name = GPIO_MOCKUP_NAME,
        },
        .probe = gpio_mockup_probe,
};

static struct platform_device *gpio_mockup_pdevs[GPIO_MOCKUP_MAX_GC];

static void gpio_mockup_unregister_pdevs(void)
{
        struct platform_device *pdev;
        int i;

        for (i = 0; i < GPIO_MOCKUP_MAX_GC; i++) {
                pdev = gpio_mockup_pdevs[i];

                if (pdev)
                        platform_device_unregister(pdev);
        }
}

static int __init gpio_mockup_init(void)
{
        struct property_entry properties[GPIO_MOCKUP_MAX_PROP];
        int i, prop, num_chips, err = 0, base;
        struct platform_device_info pdevinfo;
        struct platform_device *pdev;
        u16 ngpio;

        if ((gpio_mockup_num_ranges < 2) ||
            (gpio_mockup_num_ranges % 2) ||
            (gpio_mockup_num_ranges > GPIO_MOCKUP_MAX_RANGES))
                return -EINVAL;

        /* Each chip is described by two values. */
        num_chips = gpio_mockup_num_ranges / 2;

        /*
         * The second value in the <base GPIO - number of GPIOS> pair must
         * always be greater than 0.
         */
        for (i = 0; i < num_chips; i++) {
                if (gpio_mockup_range_ngpio(i) < 0)
                        return -EINVAL;
        }

        gpio_mockup_dbg_dir = debugfs_create_dir("gpio-mockup", NULL);

        err = platform_driver_register(&gpio_mockup_driver);
        if (err) {
                gpio_mockup_err("error registering platform driver\n");
                return err;
        }

        for (i = 0; i < num_chips; i++) {
                memset(properties, 0, sizeof(properties));
                memset(&pdevinfo, 0, sizeof(pdevinfo));
                prop = 0;

                base = gpio_mockup_range_base(i);
                if (base >= 0)
                        properties[prop++] = PROPERTY_ENTRY_U32("gpio-base",
                                                                base);

                ngpio = base < 0 ? gpio_mockup_range_ngpio(i)
                                 : gpio_mockup_range_ngpio(i) - base;
                properties[prop++] = PROPERTY_ENTRY_U16("nr-gpios", ngpio);

                if (gpio_mockup_named_lines)
                        properties[prop++] = PROPERTY_ENTRY_BOOL(
                                                "named-gpio-lines");

                pdevinfo.name = GPIO_MOCKUP_NAME;
                pdevinfo.id = i;
                pdevinfo.properties = properties;

                pdev = platform_device_register_full(&pdevinfo);
                if (IS_ERR(pdev)) {
                        gpio_mockup_err("error registering device");
                        platform_driver_unregister(&gpio_mockup_driver);
                        gpio_mockup_unregister_pdevs();
                        return PTR_ERR(pdev);
                }

                gpio_mockup_pdevs[i] = pdev;
        }

        return 0;
}

static void __exit gpio_mockup_exit(void)
{
        debugfs_remove_recursive(gpio_mockup_dbg_dir);
        platform_driver_unregister(&gpio_mockup_driver);
        gpio_mockup_unregister_pdevs();
}

module_init(gpio_mockup_init);
module_exit(gpio_mockup_exit);

MODULE_AUTHOR("Kamlakant Patel <kamlakant.patel@broadcom.com>");
MODULE_AUTHOR("Bamvor Jian Zhang <bamv2005@gmail.com>");
MODULE_AUTHOR("Bartosz Golaszewski <brgl@bgdev.pl>");
MODULE_DESCRIPTION("GPIO Testing driver");
MODULE_LICENSE("GPL v2");