// SPDX-License-Identifier: GPL-2.0
/*
 * Miscellaneous character driver for ChromeOS Embedded Controller
 *
 * Copyright 2014 Google, Inc.
 * Copyright 2019 Google LLC
 *
 * This file is a rework and part of the code is ported from
 * drivers/mfd/cros_ec_dev.c that was originally written by
 * Bill Richardson.
 */

#include <linux/init.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/kref.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/platform_data/cros_ec_chardev.h>
#include <linux/platform_data/cros_ec_commands.h>
#include <linux/platform_data/cros_ec_proto.h>
#include <linux/platform_device.h>
#include <linux/poll.h>
#include <linux/rwsem.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/uaccess.h>

#define DRV_NAME                "cros-ec-chardev"

/* Arbitrary bounded size for the event queue */
#define CROS_MAX_EVENT_LEN      PAGE_SIZE

/*
 * Platform device driver data.
 */
struct chardev_pdata {
        struct miscdevice misc;
        struct kref kref;
        struct rw_semaphore ec_dev_sem;
        struct cros_ec_device *ec_dev;
        u16 cmd_offset;
        struct blocking_notifier_head subscribers;
        struct notifier_block relay;
};

static void chardev_pdata_release(struct kref *kref)
{
        struct chardev_pdata *pdata = container_of(kref, typeof(*pdata), kref);

        kfree(pdata);
}

static int cros_ec_chardev_relay_event(struct notifier_block *nb,
                                       unsigned long queued_during_suspend,
                                       void *_notify)
{
        struct chardev_pdata *pdata = container_of(nb, typeof(*pdata), relay);

        blocking_notifier_call_chain(&pdata->subscribers, queued_during_suspend,
                                     _notify);
        return NOTIFY_OK;
}

struct chardev_priv {
        struct notifier_block notifier;
        wait_queue_head_t wait_event;
        unsigned long event_mask;
        struct list_head events;
        size_t event_len;
        struct chardev_pdata *pdata;
};

struct ec_event {
        struct list_head node;
        size_t size;
        u8 event_type;
        u8 data[];
};

static int ec_get_version(struct chardev_priv *priv, char *str, int maxlen)
{
        static const char * const current_image_name[] = {
                "unknown", "read-only", "read-write", "invalid",
        };
        struct ec_response_get_version *resp;
        struct cros_ec_command *msg;
        int ret;

        msg = kzalloc(sizeof(*msg) + sizeof(*resp), GFP_KERNEL);
        if (!msg)
                return -ENOMEM;

        msg->command = EC_CMD_GET_VERSION + priv->pdata->cmd_offset;
        msg->insize = sizeof(*resp);

        ret = cros_ec_cmd_xfer_status(priv->pdata->ec_dev, msg);
        if (ret < 0) {
                snprintf(str, maxlen,
                         "Unknown EC version, returned error: %d\n",
                         msg->result);
                goto exit;
        }

        resp = (struct ec_response_get_version *)msg->data;
        if (resp->current_image >= ARRAY_SIZE(current_image_name))
                resp->current_image = 3; /* invalid */

        snprintf(str, maxlen, "%s\n%s\n%s\n%s\n", CROS_EC_DEV_VERSION,
                 resp->version_string_ro, resp->version_string_rw,
                 current_image_name[resp->current_image]);

        ret = 0;
exit:
        kfree(msg);
        return ret;
}

static int cros_ec_chardev_mkbp_event(struct notifier_block *nb,
                                      unsigned long queued_during_suspend,
                                      void *_notify)
{
        struct chardev_priv *priv = container_of(nb, struct chardev_priv,
                                                 notifier);
        struct cros_ec_device *ec_dev;
        struct ec_event *event;
        unsigned long event_bit;
        int total_size;

        guard(rwsem_read)(&priv->pdata->ec_dev_sem);
        if (!priv->pdata->ec_dev)
                return NOTIFY_DONE;
        ec_dev = priv->pdata->ec_dev;

        event_bit = 1 << ec_dev->event_data.event_type;
        total_size = sizeof(*event) + ec_dev->event_size;

        if (!(event_bit & priv->event_mask) ||
            (priv->event_len + total_size) > CROS_MAX_EVENT_LEN)
                return NOTIFY_DONE;

        event = kzalloc(total_size, GFP_KERNEL);
        if (!event)
                return NOTIFY_DONE;

        event->size = ec_dev->event_size;
        event->event_type = ec_dev->event_data.event_type;
        memcpy(event->data, &ec_dev->event_data.data, ec_dev->event_size);

        spin_lock(&priv->wait_event.lock);
        list_add_tail(&event->node, &priv->events);
        priv->event_len += total_size;
        wake_up_locked(&priv->wait_event);
        spin_unlock(&priv->wait_event.lock);

        return NOTIFY_OK;
}

static struct ec_event *cros_ec_chardev_fetch_event(struct chardev_priv *priv,
                                                    bool fetch, bool block)
{
        struct ec_event *event;
        int err;

        spin_lock(&priv->wait_event.lock);
        if (!block && list_empty(&priv->events)) {
                event = ERR_PTR(-EWOULDBLOCK);
                goto out;
        }

        if (!fetch) {
                event = NULL;
                goto out;
        }

        err = wait_event_interruptible_locked(priv->wait_event,
                                              !list_empty(&priv->events));
        if (err) {
                event = ERR_PTR(err);
                goto out;
        }

        event = list_first_entry(&priv->events, struct ec_event, node);
        list_del(&event->node);
        priv->event_len -= sizeof(*event) + event->size;

out:
        spin_unlock(&priv->wait_event.lock);
        return event;
}

/*
 * Device file ops
 */
static int cros_ec_chardev_open(struct inode *inode, struct file *filp)
{
        struct miscdevice *mdev = filp->private_data;
        struct chardev_pdata *pdata = container_of(mdev, typeof(*pdata), misc);
        struct chardev_priv *priv;
        int ret;

        priv = kzalloc_obj(*priv);
        if (!priv)
                return -ENOMEM;

        priv->pdata = pdata;
        kref_get(&pdata->kref);
        filp->private_data = priv;
        INIT_LIST_HEAD(&priv->events);
        init_waitqueue_head(&priv->wait_event);
        nonseekable_open(inode, filp);

        priv->notifier.notifier_call = cros_ec_chardev_mkbp_event;
        ret = blocking_notifier_chain_register(&pdata->subscribers,
                                               &priv->notifier);
        if (ret) {
                dev_err(pdata->ec_dev->dev,
                        "failed to register event notifier\n");
                kref_put(&priv->pdata->kref, chardev_pdata_release);
                kfree(priv);
        }

        return ret;
}

static __poll_t cros_ec_chardev_poll(struct file *filp, poll_table *wait)
{
        struct chardev_priv *priv = filp->private_data;

        guard(rwsem_read)(&priv->pdata->ec_dev_sem);
        if (!priv->pdata->ec_dev)
                return EPOLLHUP;

        poll_wait(filp, &priv->wait_event, wait);

        if (list_empty(&priv->events))
                return 0;

        return EPOLLIN | EPOLLRDNORM;
}

static ssize_t cros_ec_chardev_read(struct file *filp, char __user *buffer,
                                     size_t length, loff_t *offset)
{
        char msg[sizeof(struct ec_response_get_version) +
                 sizeof(CROS_EC_DEV_VERSION)];
        struct chardev_priv *priv = filp->private_data;
        size_t count;
        int ret;

        guard(rwsem_read)(&priv->pdata->ec_dev_sem);
        if (!priv->pdata->ec_dev)
                return -ENODEV;

        if (priv->event_mask) { /* queued MKBP event */
                struct ec_event *event;

                event = cros_ec_chardev_fetch_event(priv, length != 0,
                                                !(filp->f_flags & O_NONBLOCK));
                if (IS_ERR(event))
                        return PTR_ERR(event);
                /*
                 * length == 0 is special - no IO is done but we check
                 * for error conditions.
                 */
                if (length == 0)
                        return 0;

                /* The event is 1 byte of type plus the payload */
                count = min(length, event->size + 1);
                ret = copy_to_user(buffer, &event->event_type, count);
                kfree(event);
                if (ret) /* the copy failed */
                        return -EFAULT;
                *offset = count;
                return count;
        }

        /*
         * Legacy behavior if no event mask is defined
         */
        if (*offset != 0)
                return 0;

        ret = ec_get_version(priv, msg, sizeof(msg));
        if (ret)
                return ret;

        count = min(length, strlen(msg));

        if (copy_to_user(buffer, msg, count))
                return -EFAULT;

        *offset = count;
        return count;
}

static int cros_ec_chardev_release(struct inode *inode, struct file *filp)
{
        struct chardev_priv *priv = filp->private_data;
        struct ec_event *event, *e;

        blocking_notifier_chain_unregister(&priv->pdata->subscribers,
                                           &priv->notifier);
        kref_put(&priv->pdata->kref, chardev_pdata_release);

        list_for_each_entry_safe(event, e, &priv->events, node) {
                list_del(&event->node);
                kfree(event);
        }
        kfree(priv);

        return 0;
}

/*
 * Ioctls
 */
static long cros_ec_chardev_ioctl_xcmd(struct chardev_priv *priv, void __user *arg)
{
        struct cros_ec_command *s_cmd;
        struct cros_ec_command u_cmd;
        long ret;

        if (copy_from_user(&u_cmd, arg, sizeof(u_cmd)))
                return -EFAULT;

        if (u_cmd.outsize > EC_MAX_MSG_BYTES ||
            u_cmd.insize > EC_MAX_MSG_BYTES)
                return -EINVAL;

        s_cmd = kzalloc(sizeof(*s_cmd) + max(u_cmd.outsize, u_cmd.insize),
                        GFP_KERNEL);
        if (!s_cmd)
                return -ENOMEM;

        if (copy_from_user(s_cmd, arg, sizeof(*s_cmd) + u_cmd.outsize)) {
                ret = -EFAULT;
                goto exit;
        }

        if (u_cmd.outsize != s_cmd->outsize ||
            u_cmd.insize != s_cmd->insize) {
                ret = -EINVAL;
                goto exit;
        }

        s_cmd->command += priv->pdata->cmd_offset;
        ret = cros_ec_cmd_xfer(priv->pdata->ec_dev, s_cmd);
        /* Only copy data to userland if data was received. */
        if (ret < 0)
                goto exit;

        if (copy_to_user(arg, s_cmd, sizeof(*s_cmd) + s_cmd->insize))
                ret = -EFAULT;
exit:
        kfree(s_cmd);
        return ret;
}

static long cros_ec_chardev_ioctl_readmem(struct chardev_priv *priv, void __user *arg)
{
        struct cros_ec_device *ec_dev = priv->pdata->ec_dev;
        struct cros_ec_readmem s_mem = { };
        long num;

        /* Not every platform supports direct reads */
        if (!ec_dev->cmd_readmem)
                return -ENOTTY;

        if (copy_from_user(&s_mem, arg, sizeof(s_mem)))
                return -EFAULT;

        if (s_mem.bytes > sizeof(s_mem.buffer))
                return -EINVAL;

        num = ec_dev->cmd_readmem(ec_dev, s_mem.offset, s_mem.bytes,
                                  s_mem.buffer);
        if (num <= 0)
                return num;

        if (copy_to_user((void __user *)arg, &s_mem, sizeof(s_mem)))
                return -EFAULT;

        return num;
}

static long cros_ec_chardev_ioctl(struct file *filp, unsigned int cmd,
                                   unsigned long arg)
{
        struct chardev_priv *priv = filp->private_data;

        guard(rwsem_read)(&priv->pdata->ec_dev_sem);
        if (!priv->pdata->ec_dev)
                return -ENODEV;

        if (_IOC_TYPE(cmd) != CROS_EC_DEV_IOC)
                return -ENOTTY;

        switch (cmd) {
        case CROS_EC_DEV_IOCXCMD:
                return cros_ec_chardev_ioctl_xcmd(priv, (void __user *)arg);
        case CROS_EC_DEV_IOCRDMEM:
                return cros_ec_chardev_ioctl_readmem(priv, (void __user *)arg);
        case CROS_EC_DEV_IOCEVENTMASK:
                priv->event_mask = arg;
                return 0;
        }

        return -ENOTTY;
}

static const struct file_operations chardev_fops = {
        .open           = cros_ec_chardev_open,
        .poll           = cros_ec_chardev_poll,
        .read           = cros_ec_chardev_read,
        .release        = cros_ec_chardev_release,
        .unlocked_ioctl = cros_ec_chardev_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = cros_ec_chardev_ioctl,
#endif
};

static int cros_ec_chardev_probe(struct platform_device *pdev)
{
        struct cros_ec_dev *ec = dev_get_drvdata(pdev->dev.parent);
        struct cros_ec_platform *ec_platform = dev_get_platdata(ec->dev);
        struct chardev_pdata *pdata;
        int ret;

        pdata = kzalloc_obj(*pdata);
        if (!pdata)
                return -ENOMEM;

        platform_set_drvdata(pdev, pdata);
        kref_init(&pdata->kref);
        init_rwsem(&pdata->ec_dev_sem);
        pdata->ec_dev = ec->ec_dev;
        pdata->cmd_offset = ec->cmd_offset;
        BLOCKING_INIT_NOTIFIER_HEAD(&pdata->subscribers);
        pdata->relay.notifier_call = cros_ec_chardev_relay_event;
        ret = blocking_notifier_chain_register(&pdata->ec_dev->event_notifier,
                                               &pdata->relay);
        if (ret) {
                dev_err(&pdev->dev, "failed to register event notifier\n");
                goto err_put_pdata;
        }

        pdata->misc.minor = MISC_DYNAMIC_MINOR;
        pdata->misc.fops = &chardev_fops;
        pdata->misc.name = ec_platform->ec_name;
        pdata->misc.parent = pdev->dev.parent;

        ret = misc_register(&pdata->misc);
        if (ret) {
                dev_err(&pdev->dev, "failed to register misc device\n");
                goto err_unregister_notifier;
        }

        return 0;
err_unregister_notifier:
        blocking_notifier_chain_unregister(&pdata->ec_dev->event_notifier,
                                           &pdata->relay);
err_put_pdata:
        kref_put(&pdata->kref, chardev_pdata_release);
        return ret;
}

static void cros_ec_chardev_remove(struct platform_device *pdev)
{
        struct chardev_pdata *pdata = platform_get_drvdata(pdev);
        struct cros_ec_device *ec_dev = pdata->ec_dev;

        /* stop new fops from being created */
        misc_deregister(&pdata->misc);
        /* stop existing fops from running */
        scoped_guard(rwsem_write, &pdata->ec_dev_sem)
                pdata->ec_dev = NULL;

        blocking_notifier_chain_unregister(&ec_dev->event_notifier,
                                           &pdata->relay);
        kref_put(&pdata->kref, chardev_pdata_release);
}

static const struct platform_device_id cros_ec_chardev_id[] = {
        { DRV_NAME, 0 },
        {}
};
MODULE_DEVICE_TABLE(platform, cros_ec_chardev_id);

static struct platform_driver cros_ec_chardev_driver = {
        .driver = {
                .name = DRV_NAME,
        },
        .probe = cros_ec_chardev_probe,
        .remove = cros_ec_chardev_remove,
        .id_table = cros_ec_chardev_id,
};

module_platform_driver(cros_ec_chardev_driver);

MODULE_AUTHOR("Enric Balletbo i Serra <enric.balletbo@collabora.com>");
MODULE_DESCRIPTION("ChromeOS EC Miscellaneous Character Driver");
MODULE_LICENSE("GPL");