// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2017 Red Hat, Inc
 */

#define pr_fmt(fmt)             KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/libps2.h>
#include <linux/i2c.h>
#include <linux/serio.h>
#include <linux/slab.h>
#include <linux/workqueue.h>
#include "psmouse.h"

struct psmouse_smbus_dev {
        struct i2c_board_info board;
        struct psmouse *psmouse;
        struct i2c_client *client;
        struct list_head node;
        bool dead;
        bool need_deactivate;
};

static LIST_HEAD(psmouse_smbus_list);
static DEFINE_MUTEX(psmouse_smbus_mutex);

static struct workqueue_struct *psmouse_smbus_wq;

static void psmouse_smbus_check_adapter(struct i2c_adapter *adapter)
{
        struct psmouse_smbus_dev *smbdev;

        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_HOST_NOTIFY))
                return;

        guard(mutex)(&psmouse_smbus_mutex);

        list_for_each_entry(smbdev, &psmouse_smbus_list, node) {
                if (smbdev->dead)
                        continue;

                if (smbdev->client)
                        continue;

                /*
                 * Here would be a good place to check if device is actually
                 * present, but it seems that SMBus will not respond unless we
                 * fully reset PS/2 connection.  So cross our fingers, and try
                 * to switch over, hopefully our system will not have too many
                 * "host notify" I2C adapters.
                 */
                psmouse_dbg(smbdev->psmouse,
                            "SMBus candidate adapter appeared, triggering rescan\n");
                serio_rescan(smbdev->psmouse->ps2dev.serio);
        }
}

static void psmouse_smbus_detach_i2c_client(struct i2c_client *client)
{
        struct psmouse_smbus_dev *smbdev, *tmp;

        guard(mutex)(&psmouse_smbus_mutex);

        list_for_each_entry_safe(smbdev, tmp, &psmouse_smbus_list, node) {
                if (smbdev->client != client)
                        continue;

                kfree(client->dev.platform_data);
                client->dev.platform_data = NULL;

                if (!smbdev->dead) {
                        psmouse_dbg(smbdev->psmouse,
                                    "Marking SMBus companion %s as gone\n",
                                    dev_name(&smbdev->client->dev));
                        smbdev->dead = true;
                        device_link_remove(&smbdev->client->dev,
                                           &smbdev->psmouse->ps2dev.serio->dev);
                        serio_rescan(smbdev->psmouse->ps2dev.serio);
                } else {
                        list_del(&smbdev->node);
                        kfree(smbdev);
                }
        }
}

static int psmouse_smbus_notifier_call(struct notifier_block *nb,
                                       unsigned long action, void *data)
{
        struct device *dev = data;

        switch (action) {
        case BUS_NOTIFY_ADD_DEVICE:
                if (dev->type == &i2c_adapter_type)
                        psmouse_smbus_check_adapter(to_i2c_adapter(dev));
                break;

        case BUS_NOTIFY_REMOVED_DEVICE:
                if (dev->type == &i2c_client_type)
                        psmouse_smbus_detach_i2c_client(to_i2c_client(dev));
                break;
        }

        return 0;
}

static struct notifier_block psmouse_smbus_notifier = {
        .notifier_call = psmouse_smbus_notifier_call,
};

static psmouse_ret_t psmouse_smbus_process_byte(struct psmouse *psmouse)
{
        return PSMOUSE_FULL_PACKET;
}

static int psmouse_smbus_reconnect(struct psmouse *psmouse)
{
        struct psmouse_smbus_dev *smbdev = psmouse->private;

        if (smbdev->need_deactivate)
                psmouse_deactivate(psmouse);

        return 0;
}

struct psmouse_smbus_removal_work {
        struct work_struct work;
        struct i2c_client *client;
};

static void psmouse_smbus_remove_i2c_device(struct work_struct *work)
{
        struct psmouse_smbus_removal_work *rwork =
                container_of(work, struct psmouse_smbus_removal_work, work);

        dev_dbg(&rwork->client->dev, "destroying SMBus companion device\n");
        i2c_unregister_device(rwork->client);

        kfree(rwork);
}

/*
 * This schedules removal of SMBus companion device. We have to do
 * it in a separate tread to avoid deadlocking on psmouse_mutex in
 * case the device has a trackstick (which is also driven by psmouse).
 *
 * Note that this may be racing with i2c adapter removal, but we
 * can't do anything about that: i2c automatically destroys clients
 * attached to an adapter that is being removed. This has to be
 * fixed in i2c core.
 */
static void psmouse_smbus_schedule_remove(struct i2c_client *client)
{
        struct psmouse_smbus_removal_work *rwork;

        rwork = kzalloc_obj(*rwork);
        if (rwork) {
                INIT_WORK(&rwork->work, psmouse_smbus_remove_i2c_device);
                rwork->client = client;

                queue_work(psmouse_smbus_wq, &rwork->work);
        }
}

static void psmouse_smbus_disconnect(struct psmouse *psmouse)
{
        struct psmouse_smbus_dev *smbdev = psmouse->private;

        guard(mutex)(&psmouse_smbus_mutex);

        if (smbdev->dead) {
                list_del(&smbdev->node);
                kfree(smbdev);
        } else {
                smbdev->dead = true;
                device_link_remove(&smbdev->client->dev,
                                   &psmouse->ps2dev.serio->dev);
                psmouse_dbg(smbdev->psmouse,
                            "posting removal request for SMBus companion %s\n",
                            dev_name(&smbdev->client->dev));
                psmouse_smbus_schedule_remove(smbdev->client);
        }

        psmouse->private = NULL;
}

static int psmouse_smbus_create_companion(struct device *dev, void *data)
{
        struct psmouse_smbus_dev *smbdev = data;
        unsigned short addr_list[] = { smbdev->board.addr, I2C_CLIENT_END };
        struct i2c_adapter *adapter;
        struct i2c_client *client;

        adapter = i2c_verify_adapter(dev);
        if (!adapter)
                return 0;

        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_HOST_NOTIFY))
                return 0;

        client = i2c_new_scanned_device(adapter, &smbdev->board,
                                        addr_list, NULL);
        if (IS_ERR(client))
                return 0;

        /* We have our(?) device, stop iterating i2c bus. */
        smbdev->client = client;
        return 1;
}

void psmouse_smbus_cleanup(struct psmouse *psmouse)
{
        struct psmouse_smbus_dev *smbdev, *tmp;

        guard(mutex)(&psmouse_smbus_mutex);

        list_for_each_entry_safe(smbdev, tmp, &psmouse_smbus_list, node) {
                if (psmouse == smbdev->psmouse) {
                        list_del(&smbdev->node);
                        kfree(smbdev);
                }
        }
}

int psmouse_smbus_init(struct psmouse *psmouse,
                       const struct i2c_board_info *board,
                       const void *pdata, size_t pdata_size,
                       bool need_deactivate,
                       bool leave_breadcrumbs)
{
        struct psmouse_smbus_dev *smbdev;
        int error;

        smbdev = kzalloc(sizeof(*smbdev), GFP_KERNEL);
        if (!smbdev)
                return -ENOMEM;

        smbdev->psmouse = psmouse;
        smbdev->board = *board;
        smbdev->need_deactivate = need_deactivate;

        if (pdata) {
                smbdev->board.platform_data = kmemdup(pdata, pdata_size,
                                                      GFP_KERNEL);
                if (!smbdev->board.platform_data) {
                        kfree(smbdev);
                        return -ENOMEM;
                }
        }

        if (need_deactivate)
                psmouse_deactivate(psmouse);

        psmouse->private = smbdev;
        psmouse->protocol_handler = psmouse_smbus_process_byte;
        psmouse->reconnect = psmouse_smbus_reconnect;
        psmouse->fast_reconnect = psmouse_smbus_reconnect;
        psmouse->disconnect = psmouse_smbus_disconnect;
        psmouse->resync_time = 0;

        scoped_guard(mutex, &psmouse_smbus_mutex) {
                list_add_tail(&smbdev->node, &psmouse_smbus_list);
        }

        /* Bind to already existing adapters right away */
        error = i2c_for_each_dev(smbdev, psmouse_smbus_create_companion);

        if (smbdev->client) {
                /* We have our companion device */
                if (!device_link_add(&smbdev->client->dev,
                                     &psmouse->ps2dev.serio->dev,
                                     DL_FLAG_STATELESS))
                        psmouse_warn(psmouse,
                                     "failed to set up link with iSMBus companion %s\n",
                                     dev_name(&smbdev->client->dev));
                return 0;
        }

        /*
         * If we did not create i2c device we will not need platform
         * data even if we are leaving breadcrumbs.
         */
        kfree(smbdev->board.platform_data);
        smbdev->board.platform_data = NULL;

        if (error < 0 || !leave_breadcrumbs) {
                scoped_guard(mutex, &psmouse_smbus_mutex) {
                        list_del(&smbdev->node);
                }

                kfree(smbdev);
        }

        return error < 0 ? error : -EAGAIN;
}

int __init psmouse_smbus_module_init(void)
{
        int error;

        psmouse_smbus_wq = alloc_workqueue("psmouse-smbus", WQ_UNBOUND, 0);
        if (!psmouse_smbus_wq)
                return -ENOMEM;

        error = bus_register_notifier(&i2c_bus_type, &psmouse_smbus_notifier);
        if (error) {
                pr_err("failed to register i2c bus notifier: %d\n", error);
                destroy_workqueue(psmouse_smbus_wq);
                return error;
        }

        return 0;
}

void psmouse_smbus_module_exit(void)
{
        bus_unregister_notifier(&i2c_bus_type, &psmouse_smbus_notifier);
        destroy_workqueue(psmouse_smbus_wq);
}