// SPDX-License-Identifier: GPL-2.0
/*
 * RTC subsystem, sysfs interface
 *
 * Copyright (C) 2005 Tower Technologies
 * Author: Alessandro Zummo <a.zummo@towertech.it>
 */

#include <linux/kstrtox.h>
#include <linux/module.h>
#include <linux/rtc.h>

#include "rtc-core.h"

/* device attributes */

/*
 * NOTE:  RTC times displayed in sysfs use the RTC's timezone.  That's
 * ideally UTC.  However, PCs that also boot to MS-Windows normally use
 * the local time and change to match daylight savings time.  That affects
 * attributes including date, time, since_epoch, and wakealarm.
 */

static ssize_t
name_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%s %s\n", dev_driver_string(dev->parent),
                          dev_name(dev->parent));
}
static DEVICE_ATTR_RO(name);

static ssize_t
date_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        ssize_t retval;
        struct rtc_time tm;

        retval = rtc_read_time(to_rtc_device(dev), &tm);
        if (retval)
                return retval;

        return sysfs_emit(buf, "%ptRd\n", &tm);
}
static DEVICE_ATTR_RO(date);

static ssize_t
time_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        ssize_t retval;
        struct rtc_time tm;

        retval = rtc_read_time(to_rtc_device(dev), &tm);
        if (retval)
                return retval;

        return sysfs_emit(buf, "%ptRt\n", &tm);
}
static DEVICE_ATTR_RO(time);

static ssize_t
since_epoch_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        ssize_t retval;
        struct rtc_time tm;

        retval = rtc_read_time(to_rtc_device(dev), &tm);
        if (retval)
                return retval;

        return sysfs_emit(buf, "%lld\n", rtc_tm_to_time64(&tm));
}
static DEVICE_ATTR_RO(since_epoch);

static ssize_t
max_user_freq_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "%d\n", to_rtc_device(dev)->max_user_freq);
}

static ssize_t
max_user_freq_store(struct device *dev, struct device_attribute *attr,
                    const char *buf, size_t n)
{
        struct rtc_device *rtc = to_rtc_device(dev);
        unsigned long val;
        int err;

        err = kstrtoul(buf, 0, &val);
        if (err)
                return err;

        if (val >= 4096 || val == 0)
                return -EINVAL;

        rtc->max_user_freq = (int)val;

        return n;
}
static DEVICE_ATTR_RW(max_user_freq);

/**
 * hctosys_show - indicate if the given RTC set the system time
 * @dev: The device that the attribute belongs to.
 * @attr: The attribute being read.
 * @buf: The result buffer.
 *
 * buf is "1" if the system clock was set by this RTC at the last
 * boot or resume event.
 */
static ssize_t
hctosys_show(struct device *dev, struct device_attribute *attr, char *buf)
{
#ifdef CONFIG_RTC_HCTOSYS_DEVICE
        if (rtc_hctosys_ret == 0 &&
            strcmp(dev_name(&to_rtc_device(dev)->dev),
                   CONFIG_RTC_HCTOSYS_DEVICE) == 0)
                return sysfs_emit(buf, "1\n");
#endif
        return sysfs_emit(buf, "0\n");
}
static DEVICE_ATTR_RO(hctosys);

static ssize_t
wakealarm_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        ssize_t retval;
        struct rtc_wkalrm alm;

        /* Don't show disabled alarms.  For uniformity, RTC alarms are
         * conceptually one-shot, even though some common RTCs (on PCs)
         * don't actually work that way.
         *
         * NOTE: RTC implementations where the alarm doesn't match an
         * exact YYYY-MM-DD HH:MM[:SS] date *must* disable their RTC
         * alarms after they trigger, to ensure one-shot semantics.
         */
        retval = rtc_read_alarm(to_rtc_device(dev), &alm);
        if (retval)
                return retval;

        if (alm.enabled)
                return sysfs_emit(buf, "%lld\n", rtc_tm_to_time64(&alm.time));

        return 0;
}

static ssize_t
wakealarm_store(struct device *dev, struct device_attribute *attr,
                const char *buf, size_t n)
{
        ssize_t retval;
        time64_t now, alarm;
        time64_t push = 0;
        struct rtc_wkalrm alm;
        struct rtc_device *rtc = to_rtc_device(dev);
        const char *buf_ptr;
        int adjust = 0;

        /* Only request alarms that trigger in the future.  Disable them
         * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
         */
        retval = rtc_read_time(rtc, &alm.time);
        if (retval < 0)
                return retval;
        now = rtc_tm_to_time64(&alm.time);

        buf_ptr = buf;
        if (*buf_ptr == '+') {
                buf_ptr++;
                if (*buf_ptr == '=') {
                        buf_ptr++;
                        push = 1;
                } else {
                        adjust = 1;
                }
        }
        retval = kstrtos64(buf_ptr, 0, &alarm);
        if (retval)
                return retval;
        if (adjust)
                alarm += now;
        if (alarm > now || push) {
                /* Avoid accidentally clobbering active alarms; we can't
                 * entirely prevent that here, without even the minimal
                 * locking from the /dev/rtcN api.
                 */
                retval = rtc_read_alarm(rtc, &alm);
                if (retval < 0)
                        return retval;
                if (alm.enabled) {
                        if (push) {
                                push = rtc_tm_to_time64(&alm.time);
                                alarm += push;
                        } else
                                return -EBUSY;
                } else if (push)
                        return -EINVAL;
                alm.enabled = 1;
        } else {
                alm.enabled = 0;

                /* Provide a valid future alarm time.  Linux isn't EFI,
                 * this time won't be ignored when disabling the alarm.
                 */
                alarm = now + 300;
        }
        rtc_time64_to_tm(alarm, &alm.time);

        retval = rtc_set_alarm(rtc, &alm);
        return (retval < 0) ? retval : n;
}
static DEVICE_ATTR_RW(wakealarm);

static ssize_t
offset_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        ssize_t retval;
        long offset;

        retval = rtc_read_offset(to_rtc_device(dev), &offset);
        if (retval)
                return retval;

        return sysfs_emit(buf, "%ld\n", offset);
}

static ssize_t
offset_store(struct device *dev, struct device_attribute *attr,
             const char *buf, size_t n)
{
        ssize_t retval;
        long offset;

        retval = kstrtol(buf, 10, &offset);
        if (retval == 0)
                retval = rtc_set_offset(to_rtc_device(dev), offset);

        return (retval < 0) ? retval : n;
}
static DEVICE_ATTR_RW(offset);

static ssize_t
range_show(struct device *dev, struct device_attribute *attr, char *buf)
{
        return sysfs_emit(buf, "[%lld,%llu]\n", to_rtc_device(dev)->range_min,
                          to_rtc_device(dev)->range_max);
}
static DEVICE_ATTR_RO(range);

static struct attribute *rtc_attrs[] = {
        &dev_attr_name.attr,
        &dev_attr_date.attr,
        &dev_attr_time.attr,
        &dev_attr_since_epoch.attr,
        &dev_attr_max_user_freq.attr,
        &dev_attr_hctosys.attr,
        &dev_attr_wakealarm.attr,
        &dev_attr_offset.attr,
        &dev_attr_range.attr,
        NULL,
};

/* The reason to trigger an alarm with no process watching it (via sysfs)
 * is its side effect:  waking from a system state like suspend-to-RAM or
 * suspend-to-disk.  So: no attribute unless that side effect is possible.
 * (Userspace may disable that mechanism later.)
 */
static bool rtc_does_wakealarm(struct rtc_device *rtc)
{
        if (!device_can_wakeup(rtc->dev.parent))
                return false;

        return !!test_bit(RTC_FEATURE_ALARM, rtc->features);
}

static umode_t rtc_attr_is_visible(struct kobject *kobj,
                                   struct attribute *attr, int n)
{
        struct device *dev = kobj_to_dev(kobj);
        struct rtc_device *rtc = to_rtc_device(dev);
        umode_t mode = attr->mode;

        if (attr == &dev_attr_wakealarm.attr) {
                if (!rtc_does_wakealarm(rtc))
                        mode = 0;
        } else if (attr == &dev_attr_offset.attr) {
                if (!rtc->ops->set_offset)
                        mode = 0;
        } else if (attr == &dev_attr_range.attr) {
                if (!(rtc->range_max - rtc->range_min))
                        mode = 0;
        }

        return mode;
}

static struct attribute_group rtc_attr_group = {
        .is_visible     = rtc_attr_is_visible,
        .attrs          = rtc_attrs,
};
__ATTRIBUTE_GROUPS(rtc_attr);

const struct attribute_group **rtc_get_dev_attribute_groups(void)
{
        return rtc_attr_groups;
}

int rtc_add_groups(struct rtc_device *rtc, const struct attribute_group **grps)
{
        size_t old_cnt = 0, add_cnt = 0, new_cnt;
        const struct attribute_group **groups, **old;

        if (grps) {
                for (groups = grps; *groups; groups++)
                        add_cnt++;
                /* No need to modify current groups if nothing new is provided */
                if (add_cnt == 0)
                        return 0;
        } else {
                return -EINVAL;
        }

        groups = rtc->dev.groups;
        if (groups)
                for (; *groups; groups++)
                        old_cnt++;

        new_cnt = old_cnt + add_cnt + 1;
        groups = devm_kcalloc(&rtc->dev, new_cnt, sizeof(*groups), GFP_KERNEL);
        if (!groups)
                return -ENOMEM;
        memcpy(groups, rtc->dev.groups, old_cnt * sizeof(*groups));
        memcpy(groups + old_cnt, grps, add_cnt * sizeof(*groups));
        groups[old_cnt + add_cnt] = NULL;

        old = rtc->dev.groups;
        rtc->dev.groups = groups;
        if (old && old != rtc_attr_groups)
                devm_kfree(&rtc->dev, old);

        return 0;
}
EXPORT_SYMBOL(rtc_add_groups);

int rtc_add_group(struct rtc_device *rtc, const struct attribute_group *grp)
{
        const struct attribute_group *groups[] = { grp, NULL };

        return rtc_add_groups(rtc, groups);
}
EXPORT_SYMBOL(rtc_add_group);