// SPDX-License-Identifier: GPL-2.0
/*
 * RTC subsystem, dev interface
 *
 * Copyright (C) 2005 Tower Technologies
 * Author: Alessandro Zummo <a.zummo@towertech.it>
 *
 * based on arch/arm/common/rtctime.c
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/rtc.h>
#include <linux/sched/signal.h>
#include "rtc-core.h"

static dev_t rtc_devt;

#define RTC_DEV_MAX 16 /* 16 RTCs should be enough for everyone... */

static int rtc_dev_open(struct inode *inode, struct file *file)
{
        struct rtc_device *rtc = container_of(inode->i_cdev,
                                        struct rtc_device, char_dev);

        if (test_and_set_bit_lock(RTC_DEV_BUSY, &rtc->flags))
                return -EBUSY;

        file->private_data = rtc;

        spin_lock_irq(&rtc->irq_lock);
        rtc->irq_data = 0;
        spin_unlock_irq(&rtc->irq_lock);

        return 0;
}

#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
/*
 * Routine to poll RTC seconds field for change as often as possible,
 * after first RTC_UIE use timer to reduce polling
 */
static void rtc_uie_task(struct work_struct *work)
{
        struct rtc_device *rtc =
                container_of(work, struct rtc_device, uie_task);
        struct rtc_time tm;
        int num = 0;
        int err;

        err = rtc_read_time(rtc, &tm);

        spin_lock_irq(&rtc->irq_lock);
        if (rtc->stop_uie_polling || err) {
                rtc->uie_task_active = 0;
        } else if (rtc->oldsecs != tm.tm_sec) {
                num = (tm.tm_sec + 60 - rtc->oldsecs) % 60;
                rtc->oldsecs = tm.tm_sec;
                rtc->uie_timer.expires = jiffies + HZ - (HZ / 10);
                rtc->uie_timer_active = 1;
                rtc->uie_task_active = 0;
                add_timer(&rtc->uie_timer);
        } else if (schedule_work(&rtc->uie_task) == 0) {
                rtc->uie_task_active = 0;
        }
        spin_unlock_irq(&rtc->irq_lock);
        if (num)
                rtc_handle_legacy_irq(rtc, num, RTC_UF);
}

static void rtc_uie_timer(struct timer_list *t)
{
        struct rtc_device *rtc = from_timer(rtc, t, uie_timer);
        unsigned long flags;

        spin_lock_irqsave(&rtc->irq_lock, flags);
        rtc->uie_timer_active = 0;
        rtc->uie_task_active = 1;
        if ((schedule_work(&rtc->uie_task) == 0))
                rtc->uie_task_active = 0;
        spin_unlock_irqrestore(&rtc->irq_lock, flags);
}

static int clear_uie(struct rtc_device *rtc)
{
        spin_lock_irq(&rtc->irq_lock);
        if (rtc->uie_irq_active) {
                rtc->stop_uie_polling = 1;
                if (rtc->uie_timer_active) {
                        spin_unlock_irq(&rtc->irq_lock);
                        del_timer_sync(&rtc->uie_timer);
                        spin_lock_irq(&rtc->irq_lock);
                        rtc->uie_timer_active = 0;
                }
                if (rtc->uie_task_active) {
                        spin_unlock_irq(&rtc->irq_lock);
                        flush_scheduled_work();
                        spin_lock_irq(&rtc->irq_lock);
                }
                rtc->uie_irq_active = 0;
        }
        spin_unlock_irq(&rtc->irq_lock);
        return 0;
}

static int set_uie(struct rtc_device *rtc)
{
        struct rtc_time tm;
        int err;

        err = rtc_read_time(rtc, &tm);
        if (err)
                return err;
        spin_lock_irq(&rtc->irq_lock);
        if (!rtc->uie_irq_active) {
                rtc->uie_irq_active = 1;
                rtc->stop_uie_polling = 0;
                rtc->oldsecs = tm.tm_sec;
                rtc->uie_task_active = 1;
                if (schedule_work(&rtc->uie_task) == 0)
                        rtc->uie_task_active = 0;
        }
        rtc->irq_data = 0;
        spin_unlock_irq(&rtc->irq_lock);
        return 0;
}

int rtc_dev_update_irq_enable_emul(struct rtc_device *rtc, unsigned int enabled)
{
        if (enabled)
                return set_uie(rtc);
        else
                return clear_uie(rtc);
}
EXPORT_SYMBOL(rtc_dev_update_irq_enable_emul);

#endif /* CONFIG_RTC_INTF_DEV_UIE_EMUL */

static ssize_t
rtc_dev_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
        struct rtc_device *rtc = file->private_data;

        DECLARE_WAITQUEUE(wait, current);
        unsigned long data;
        ssize_t ret;

        if (count != sizeof(unsigned int) && count < sizeof(unsigned long))
                return -EINVAL;

        add_wait_queue(&rtc->irq_queue, &wait);
        do {
                __set_current_state(TASK_INTERRUPTIBLE);

                spin_lock_irq(&rtc->irq_lock);
                data = rtc->irq_data;
                rtc->irq_data = 0;
                spin_unlock_irq(&rtc->irq_lock);

                if (data != 0) {
                        ret = 0;
                        break;
                }
                if (file->f_flags & O_NONBLOCK) {
                        ret = -EAGAIN;
                        break;
                }
                if (signal_pending(current)) {
                        ret = -ERESTARTSYS;
                        break;
                }
                schedule();
        } while (1);
        set_current_state(TASK_RUNNING);
        remove_wait_queue(&rtc->irq_queue, &wait);

        if (ret == 0) {
                if (sizeof(int) != sizeof(long) &&
                    count == sizeof(unsigned int))
                        ret = put_user(data, (unsigned int __user *)buf) ?:
                                sizeof(unsigned int);
                else
                        ret = put_user(data, (unsigned long __user *)buf) ?:
                                sizeof(unsigned long);
        }
        return ret;
}

static __poll_t rtc_dev_poll(struct file *file, poll_table *wait)
{
        struct rtc_device *rtc = file->private_data;
        unsigned long data;

        poll_wait(file, &rtc->irq_queue, wait);

        data = rtc->irq_data;

        return (data != 0) ? (EPOLLIN | EPOLLRDNORM) : 0;
}

static long rtc_dev_ioctl(struct file *file,
                          unsigned int cmd, unsigned long arg)
{
        int err = 0;
        struct rtc_device *rtc = file->private_data;
        const struct rtc_class_ops *ops = rtc->ops;
        struct rtc_time tm;
        struct rtc_wkalrm alarm;
        void __user *uarg = (void __user *)arg;

        err = mutex_lock_interruptible(&rtc->ops_lock);
        if (err)
                return err;

        /* check that the calling task has appropriate permissions
         * for certain ioctls. doing this check here is useful
         * to avoid duplicate code in each driver.
         */
        switch (cmd) {
        case RTC_EPOCH_SET:
        case RTC_SET_TIME:
                if (!capable(CAP_SYS_TIME))
                        err = -EACCES;
                break;

        case RTC_IRQP_SET:
                if (arg > rtc->max_user_freq && !capable(CAP_SYS_RESOURCE))
                        err = -EACCES;
                break;

        case RTC_PIE_ON:
                if (rtc->irq_freq > rtc->max_user_freq &&
                    !capable(CAP_SYS_RESOURCE))
                        err = -EACCES;
                break;
        }

        if (err)
                goto done;

        /*
         * Drivers *SHOULD NOT* provide ioctl implementations
         * for these requests.  Instead, provide methods to
         * support the following code, so that the RTC's main
         * features are accessible without using ioctls.
         *
         * RTC and alarm times will be in UTC, by preference,
         * but dual-booting with MS-Windows implies RTCs must
         * use the local wall clock time.
         */

        switch (cmd) {
        case RTC_ALM_READ:
                mutex_unlock(&rtc->ops_lock);

                err = rtc_read_alarm(rtc, &alarm);
                if (err < 0)
                        return err;

                if (copy_to_user(uarg, &alarm.time, sizeof(tm)))
                        err = -EFAULT;
                return err;

        case RTC_ALM_SET:
                mutex_unlock(&rtc->ops_lock);

                if (copy_from_user(&alarm.time, uarg, sizeof(tm)))
                        return -EFAULT;

                alarm.enabled = 0;
                alarm.pending = 0;
                alarm.time.tm_wday = -1;
                alarm.time.tm_yday = -1;
                alarm.time.tm_isdst = -1;

                /* RTC_ALM_SET alarms may be up to 24 hours in the future.
                 * Rather than expecting every RTC to implement "don't care"
                 * for day/month/year fields, just force the alarm to have
                 * the right values for those fields.
                 *
                 * RTC_WKALM_SET should be used instead.  Not only does it
                 * eliminate the need for a separate RTC_AIE_ON call, it
                 * doesn't have the "alarm 23:59:59 in the future" race.
                 *
                 * NOTE:  some legacy code may have used invalid fields as
                 * wildcards, exposing hardware "periodic alarm" capabilities.
                 * Not supported here.
                 */
                {
                        time64_t now, then;

                        err = rtc_read_time(rtc, &tm);
                        if (err < 0)
                                return err;
                        now = rtc_tm_to_time64(&tm);

                        alarm.time.tm_mday = tm.tm_mday;
                        alarm.time.tm_mon = tm.tm_mon;
                        alarm.time.tm_year = tm.tm_year;
                        err  = rtc_valid_tm(&alarm.time);
                        if (err < 0)
                                return err;
                        then = rtc_tm_to_time64(&alarm.time);

                        /* alarm may need to wrap into tomorrow */
                        if (then < now) {
                                rtc_time64_to_tm(now + 24 * 60 * 60, &tm);
                                alarm.time.tm_mday = tm.tm_mday;
                                alarm.time.tm_mon = tm.tm_mon;
                                alarm.time.tm_year = tm.tm_year;
                        }
                }

                return rtc_set_alarm(rtc, &alarm);

        case RTC_RD_TIME:
                mutex_unlock(&rtc->ops_lock);

                err = rtc_read_time(rtc, &tm);
                if (err < 0)
                        return err;

                if (copy_to_user(uarg, &tm, sizeof(tm)))
                        err = -EFAULT;
                return err;

        case RTC_SET_TIME:
                mutex_unlock(&rtc->ops_lock);

                if (copy_from_user(&tm, uarg, sizeof(tm)))
                        return -EFAULT;

                return rtc_set_time(rtc, &tm);

        case RTC_PIE_ON:
                err = rtc_irq_set_state(rtc, 1);
                break;

        case RTC_PIE_OFF:
                err = rtc_irq_set_state(rtc, 0);
                break;

        case RTC_AIE_ON:
                mutex_unlock(&rtc->ops_lock);
                return rtc_alarm_irq_enable(rtc, 1);

        case RTC_AIE_OFF:
                mutex_unlock(&rtc->ops_lock);
                return rtc_alarm_irq_enable(rtc, 0);

        case RTC_UIE_ON:
                mutex_unlock(&rtc->ops_lock);
                return rtc_update_irq_enable(rtc, 1);

        case RTC_UIE_OFF:
                mutex_unlock(&rtc->ops_lock);
                return rtc_update_irq_enable(rtc, 0);

        case RTC_IRQP_SET:
                err = rtc_irq_set_freq(rtc, arg);
                break;

        case RTC_IRQP_READ:
                err = put_user(rtc->irq_freq, (unsigned long __user *)uarg);
                break;

        case RTC_WKALM_SET:
                mutex_unlock(&rtc->ops_lock);
                if (copy_from_user(&alarm, uarg, sizeof(alarm)))
                        return -EFAULT;

                return rtc_set_alarm(rtc, &alarm);

        case RTC_WKALM_RD:
                mutex_unlock(&rtc->ops_lock);
                err = rtc_read_alarm(rtc, &alarm);
                if (err < 0)
                        return err;

                if (copy_to_user(uarg, &alarm, sizeof(alarm)))
                        err = -EFAULT;
                return err;

        default:
                /* Finally try the driver's ioctl interface */
                if (ops->ioctl) {
                        err = ops->ioctl(rtc->dev.parent, cmd, arg);
                        if (err == -ENOIOCTLCMD)
                                err = -ENOTTY;
                } else {
                        err = -ENOTTY;
                }
                break;
        }

done:
        mutex_unlock(&rtc->ops_lock);
        return err;
}

static int rtc_dev_fasync(int fd, struct file *file, int on)
{
        struct rtc_device *rtc = file->private_data;

        return fasync_helper(fd, file, on, &rtc->async_queue);
}

static int rtc_dev_release(struct inode *inode, struct file *file)
{
        struct rtc_device *rtc = file->private_data;

        /* We shut down the repeating IRQs that userspace enabled,
         * since nothing is listening to them.
         *  - Update (UIE) ... currently only managed through ioctls
         *  - Periodic (PIE) ... also used through rtc_*() interface calls
         *
         * Leave the alarm alone; it may be set to trigger a system wakeup
         * later, or be used by kernel code, and is a one-shot event anyway.
         */

        /* Keep ioctl until all drivers are converted */
        rtc_dev_ioctl(file, RTC_UIE_OFF, 0);
        rtc_update_irq_enable(rtc, 0);
        rtc_irq_set_state(rtc, 0);

        clear_bit_unlock(RTC_DEV_BUSY, &rtc->flags);
        return 0;
}

static const struct file_operations rtc_dev_fops = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
        .read           = rtc_dev_read,
        .poll           = rtc_dev_poll,
        .unlocked_ioctl = rtc_dev_ioctl,
        .open           = rtc_dev_open,
        .release        = rtc_dev_release,
        .fasync         = rtc_dev_fasync,
};

/* insertion/removal hooks */

void rtc_dev_prepare(struct rtc_device *rtc)
{
        if (!rtc_devt)
                return;

        if (rtc->id >= RTC_DEV_MAX) {
                dev_dbg(&rtc->dev, "too many RTC devices\n");
                return;
        }

        rtc->dev.devt = MKDEV(MAJOR(rtc_devt), rtc->id);

#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
        INIT_WORK(&rtc->uie_task, rtc_uie_task);
        timer_setup(&rtc->uie_timer, rtc_uie_timer, 0);
#endif

        cdev_init(&rtc->char_dev, &rtc_dev_fops);
        rtc->char_dev.owner = rtc->owner;
}

void __init rtc_dev_init(void)
{
        int err;

        err = alloc_chrdev_region(&rtc_devt, 0, RTC_DEV_MAX, "rtc");
        if (err < 0)
                pr_err("failed to allocate char dev region\n");
}

void __exit rtc_dev_exit(void)
{
        if (rtc_devt)
                unregister_chrdev_region(rtc_devt, RTC_DEV_MAX);
}