/*
 * RTC subsystem, sysfs interface
 *
 * Copyright (C) 2005 Tower Technologies
 * Author: Alessandro Zummo <a.zummo@towertech.it>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
*/

#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
rtc_sysfs_show_name(struct device *dev, struct device_attribute *attr,
                char *buf)
{
        return sprintf(buf, "%s\n", to_rtc_device(dev)->name);
}

static ssize_t
rtc_sysfs_show_date(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 == 0) {
                retval = sprintf(buf, "%04d-%02d-%02d\n",
                        tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday);
        }

        return retval;
}

static ssize_t
rtc_sysfs_show_time(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 == 0) {
                retval = sprintf(buf, "%02d:%02d:%02d\n",
                        tm.tm_hour, tm.tm_min, tm.tm_sec);
        }

        return retval;
}

static ssize_t
rtc_sysfs_show_since_epoch(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 == 0) {
                unsigned long time;
                rtc_tm_to_time(&tm, &time);
                retval = sprintf(buf, "%lu\n", time);
        }

        return retval;
}

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

static ssize_t
rtc_sysfs_set_max_user_freq(struct device *dev, struct device_attribute *attr,
                const char *buf, size_t n)
{
        struct rtc_device *rtc = to_rtc_device(dev);
        unsigned long val = simple_strtoul(buf, NULL, 0);

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

        rtc->max_user_freq = (int)val;

        return n;
}

static struct device_attribute rtc_attrs[] = {
        __ATTR(name, S_IRUGO, rtc_sysfs_show_name, NULL),
        __ATTR(date, S_IRUGO, rtc_sysfs_show_date, NULL),
        __ATTR(time, S_IRUGO, rtc_sysfs_show_time, NULL),
        __ATTR(since_epoch, S_IRUGO, rtc_sysfs_show_since_epoch, NULL),
        __ATTR(max_user_freq, S_IRUGO | S_IWUSR, rtc_sysfs_show_max_user_freq,
                        rtc_sysfs_set_max_user_freq),
        { },
};

static ssize_t
rtc_sysfs_show_wakealarm(struct device *dev, struct device_attribute *attr,
                char *buf)
{
        ssize_t retval;
        unsigned long alarm;
        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 == 0 && alm.enabled) {
                rtc_tm_to_time(&alm.time, &alarm);
                retval = sprintf(buf, "%lu\n", alarm);
        }

        return retval;
}

static ssize_t
rtc_sysfs_set_wakealarm(struct device *dev, struct device_attribute *attr,
                const char *buf, size_t n)
{
        ssize_t retval;
        unsigned long now, alarm;
        struct rtc_wkalrm alm;
        struct rtc_device *rtc = to_rtc_device(dev);
        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;
        rtc_tm_to_time(&alm.time, &now);

        buf_ptr = (char *)buf;
        if (*buf_ptr == '+') {
                buf_ptr++;
                adjust = 1;
        }
        alarm = simple_strtoul(buf_ptr, NULL, 0);
        if (adjust) {
                alarm += now;
        }
        if (alarm > now) {
                /* 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)
                        return -EBUSY;

                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_time_to_tm(alarm, &alm.time);

        retval = rtc_set_alarm(rtc, &alm);
        return (retval < 0) ? retval : n;
}
static DEVICE_ATTR(wakealarm, S_IRUGO | S_IWUSR,
                rtc_sysfs_show_wakealarm, rtc_sysfs_set_wakealarm);


/* 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 inline int rtc_does_wakealarm(struct rtc_device *rtc)
{
        if (!device_can_wakeup(rtc->dev.parent))
                return 0;
        return rtc->ops->set_alarm != NULL;
}


void rtc_sysfs_add_device(struct rtc_device *rtc)
{
        int err;

        /* not all RTCs support both alarms and wakeup */
        if (!rtc_does_wakealarm(rtc))
                return;

        err = device_create_file(&rtc->dev, &dev_attr_wakealarm);
        if (err)
                dev_err(rtc->dev.parent,
                        "failed to create alarm attribute, %d\n", err);
}

void rtc_sysfs_del_device(struct rtc_device *rtc)
{
        /* REVISIT did we add it successfully? */
        if (rtc_does_wakealarm(rtc))
                device_remove_file(&rtc->dev, &dev_attr_wakealarm);
}

void __init rtc_sysfs_init(struct class *rtc_class)
{
        rtc_class->dev_attrs = rtc_attrs;
}