// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (c) 2004 Evgeniy Polyakov <zbr@ioremap.net>
 */

#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/delay.h>
#include <linux/kthread.h>
#include <linux/slab.h>
#include <linux/sched/signal.h>
#include <linux/export.h>
#include <linux/moduleparam.h>

#include "w1_internal.h"
#include "w1_netlink.h"

static int w1_search_count = -1; /* Default is continual scan */
module_param_named(search_count, w1_search_count, int, 0);

static int w1_enable_pullup = 1;
module_param_named(enable_pullup, w1_enable_pullup, int, 0);

static struct w1_master *w1_alloc_dev(u32 id, int slave_count, int slave_ttl,
                                       struct device_driver *driver,
                                       struct device *device)
{
        struct w1_master *dev;
        int err;

        /*
         * We are in process context(kernel thread), so can sleep.
         */
        dev = kzalloc(sizeof(struct w1_master) + sizeof(struct w1_bus_master), GFP_KERNEL);
        if (!dev) {
                pr_err("Failed to allocate %zd bytes for new w1 device.\n",
                        sizeof(struct w1_master));
                return NULL;
        }


        dev->bus_master = (struct w1_bus_master *)(dev + 1);

        dev->owner              = THIS_MODULE;
        dev->max_slave_count    = slave_count;
        dev->slave_count        = 0;
        dev->attempts           = 0;
        dev->initialized        = 0;
        dev->id                 = id;
        dev->slave_ttl          = slave_ttl;
        dev->search_count       = w1_search_count;
        dev->enable_pullup      = w1_enable_pullup;

        /* 1 for w1_process to decrement
         * 1 for __w1_remove_master_device to decrement
         */
        atomic_set(&dev->refcnt, 2);

        INIT_LIST_HEAD(&dev->slist);
        INIT_LIST_HEAD(&dev->async_list);
        mutex_init(&dev->mutex);
        mutex_init(&dev->bus_mutex);
        mutex_init(&dev->list_mutex);

        memcpy(&dev->dev, device, sizeof(struct device));
        dev_set_name(&dev->dev, "w1_bus_master%u", dev->id);
        snprintf(dev->name, sizeof(dev->name), "w1_bus_master%u", dev->id);
        dev->dev.init_name = dev->name;

        dev->driver = driver;

        dev->seq = 1;

        err = device_register(&dev->dev);
        if (err) {
                pr_err("Failed to register master device. err=%d\n", err);
                put_device(&dev->dev);
                dev = NULL;
        }

        return dev;
}

static void w1_free_dev(struct w1_master *dev)
{
        device_unregister(&dev->dev);
}

/**
 * w1_add_master_device() - registers a new master device
 * @master:     master bus device to register
 */
int w1_add_master_device(struct w1_bus_master *master)
{
        struct w1_master *dev, *entry;
        int retval = 0;
        struct w1_netlink_msg msg;
        int id, found;

        /* validate minimum functionality */
        if (!(master->touch_bit && master->reset_bus) &&
            !(master->write_bit && master->read_bit) &&
            !(master->write_byte && master->read_byte && master->reset_bus)) {
                pr_err("w1_add_master_device: invalid function set\n");
                return(-EINVAL);
        }

        /* Lock until the device is added (or not) to w1_masters. */
        mutex_lock(&w1_mlock);
        /* Search for the first available id (starting at 1). */
        id = 0;
        do {
                ++id;
                found = 0;
                list_for_each_entry(entry, &w1_masters, w1_master_entry) {
                        if (entry->id == id) {
                                found = 1;
                                break;
                        }
                }
        } while (found);

        dev = w1_alloc_dev(id, w1_max_slave_count, w1_max_slave_ttl,
                &w1_master_driver, &w1_master_device);
        if (!dev) {
                mutex_unlock(&w1_mlock);
                return -ENOMEM;
        }

        retval =  w1_create_master_attributes(dev);
        if (retval) {
                mutex_unlock(&w1_mlock);
                goto err_out_free_dev;
        }

        memcpy(dev->bus_master, master, sizeof(struct w1_bus_master));

        dev->initialized = 1;

        dev->thread = kthread_run(&w1_process, dev, "%s", dev->name);
        if (IS_ERR(dev->thread)) {
                retval = PTR_ERR(dev->thread);
                dev_err(&dev->dev,
                         "Failed to create new kernel thread. err=%d\n",
                         retval);
                mutex_unlock(&w1_mlock);
                goto err_out_rm_attr;
        }

        list_add(&dev->w1_master_entry, &w1_masters);
        mutex_unlock(&w1_mlock);

        memset(&msg, 0, sizeof(msg));
        msg.id.mst.id = dev->id;
        msg.type = W1_MASTER_ADD;
        w1_netlink_send(dev, &msg);

        return 0;

#if 0 /* Thread cleanup code, not required currently. */
err_out_kill_thread:
        set_bit(W1_ABORT_SEARCH, &dev->flags);
        kthread_stop(dev->thread);
#endif
err_out_rm_attr:
        w1_destroy_master_attributes(dev);
err_out_free_dev:
        w1_free_dev(dev);

        return retval;
}
EXPORT_SYMBOL(w1_add_master_device);

void __w1_remove_master_device(struct w1_master *dev)
{
        struct w1_netlink_msg msg;
        struct w1_slave *sl, *sln;

        mutex_lock(&w1_mlock);
        list_del(&dev->w1_master_entry);
        mutex_unlock(&w1_mlock);

        set_bit(W1_ABORT_SEARCH, &dev->flags);
        kthread_stop(dev->thread);

        mutex_lock(&dev->mutex);
        mutex_lock(&dev->list_mutex);
        list_for_each_entry_safe(sl, sln, &dev->slist, w1_slave_entry) {
                mutex_unlock(&dev->list_mutex);
                w1_slave_detach(sl);
                mutex_lock(&dev->list_mutex);
        }
        w1_destroy_master_attributes(dev);
        mutex_unlock(&dev->list_mutex);
        mutex_unlock(&dev->mutex);
        atomic_dec(&dev->refcnt);

        while (atomic_read(&dev->refcnt)) {
                dev_info(&dev->dev, "Waiting for %s to become free: refcnt=%d.\n",
                                dev->name, atomic_read(&dev->refcnt));

                if (msleep_interruptible(1000))
                        flush_signals(current);
                mutex_lock(&dev->list_mutex);
                w1_process_callbacks(dev);
                mutex_unlock(&dev->list_mutex);
        }
        mutex_lock(&dev->list_mutex);
        w1_process_callbacks(dev);
        mutex_unlock(&dev->list_mutex);

        memset(&msg, 0, sizeof(msg));
        msg.id.mst.id = dev->id;
        msg.type = W1_MASTER_REMOVE;
        w1_netlink_send(dev, &msg);

        w1_free_dev(dev);
}

/**
 * w1_remove_master_device() - unregister a master device
 * @bm: master bus device to remove
 */
void w1_remove_master_device(struct w1_bus_master *bm)
{
        struct w1_master *dev, *found = NULL;

        list_for_each_entry(dev, &w1_masters, w1_master_entry) {
                if (!dev->initialized)
                        continue;

                if (dev->bus_master->data == bm->data) {
                        found = dev;
                        break;
                }
        }

        if (!found) {
                pr_err("Device doesn't exist.\n");
                return;
        }

        __w1_remove_master_device(found);
}
EXPORT_SYMBOL(w1_remove_master_device);