/*
 * rtc-efi: RTC Class Driver for EFI-based systems
 *
 * Copyright (C) 2009 Hewlett-Packard Development Company, L.P.
 *
 * Author: dann frazier <dannf@hp.com>
 * Based on efirtc.c by Stephane Eranian
 *
 *  This program is free software; you can redistribute  it and/or modify it
 *  under  the terms of  the GNU General  Public License as published by the
 *  Free Software Foundation;  either version 2 of the  License, or (at your
 *  option) any later version.
 *
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/time.h>
#include <linux/platform_device.h>
#include <linux/rtc.h>
#include <linux/efi.h>

#define EFI_ISDST (EFI_TIME_ADJUST_DAYLIGHT|EFI_TIME_IN_DAYLIGHT)
/*
 * EFI Epoch is 1/1/1998
 */
#define EFI_RTC_EPOCH           1998

/*
 * returns day of the year [0-365]
 */
static inline int
compute_yday(efi_time_t *eft)
{
        /* efi_time_t.month is in the [1-12] so, we need -1 */
        return rtc_year_days(eft->day - 1, eft->month - 1, eft->year);
}
/*
 * returns day of the week [0-6] 0=Sunday
 *
 * Don't try to provide a year that's before 1998, please !
 */
static int
compute_wday(efi_time_t *eft)
{
        int y;
        int ndays = 0;

        if (eft->year < 1998) {
                printk(KERN_ERR "efirtc: EFI year < 1998, invalid date\n");
                return -1;
        }

        for (y = EFI_RTC_EPOCH; y < eft->year; y++)
                ndays += 365 + (is_leap_year(y) ? 1 : 0);

        ndays += compute_yday(eft);

        /*
         * 4=1/1/1998 was a Thursday
         */
        return (ndays + 4) % 7;
}

static void
convert_to_efi_time(struct rtc_time *wtime, efi_time_t *eft)
{
        eft->year       = wtime->tm_year + 1900;
        eft->month      = wtime->tm_mon + 1;
        eft->day        = wtime->tm_mday;
        eft->hour       = wtime->tm_hour;
        eft->minute     = wtime->tm_min;
        eft->second     = wtime->tm_sec;
        eft->nanosecond = 0;
        eft->daylight   = wtime->tm_isdst ? EFI_ISDST : 0;
        eft->timezone   = EFI_UNSPECIFIED_TIMEZONE;
}

static void
convert_from_efi_time(efi_time_t *eft, struct rtc_time *wtime)
{
        memset(wtime, 0, sizeof(*wtime));
        wtime->tm_sec  = eft->second;
        wtime->tm_min  = eft->minute;
        wtime->tm_hour = eft->hour;
        wtime->tm_mday = eft->day;
        wtime->tm_mon  = eft->month - 1;
        wtime->tm_year = eft->year - 1900;

        /* day of the week [0-6], Sunday=0 */
        wtime->tm_wday = compute_wday(eft);

        /* day in the year [1-365]*/
        wtime->tm_yday = compute_yday(eft);


        switch (eft->daylight & EFI_ISDST) {
        case EFI_ISDST:
                wtime->tm_isdst = 1;
                break;
        case EFI_TIME_ADJUST_DAYLIGHT:
                wtime->tm_isdst = 0;
                break;
        default:
                wtime->tm_isdst = -1;
        }
}

static int efi_read_alarm(struct device *dev, struct rtc_wkalrm *wkalrm)
{
        efi_time_t eft;
        efi_status_t status;

        /*
         * As of EFI v1.10, this call always returns an unsupported status
         */
        status = efi.get_wakeup_time((efi_bool_t *)&wkalrm->enabled,
                                     (efi_bool_t *)&wkalrm->pending, &eft);

        if (status != EFI_SUCCESS)
                return -EINVAL;

        convert_from_efi_time(&eft, &wkalrm->time);

        return rtc_valid_tm(&wkalrm->time);
}

static int efi_set_alarm(struct device *dev, struct rtc_wkalrm *wkalrm)
{
        efi_time_t eft;
        efi_status_t status;

        convert_to_efi_time(&wkalrm->time, &eft);

        /*
         * XXX Fixme:
         * As of EFI 0.92 with the firmware I have on my
         * machine this call does not seem to work quite
         * right
         *
         * As of v1.10, this call always returns an unsupported status
         */
        status = efi.set_wakeup_time((efi_bool_t)wkalrm->enabled, &eft);

        printk(KERN_WARNING "write status is %d\n", (int)status);

        return status == EFI_SUCCESS ? 0 : -EINVAL;
}

static int efi_read_time(struct device *dev, struct rtc_time *tm)
{
        efi_status_t status;
        efi_time_t eft;
        efi_time_cap_t cap;

        status = efi.get_time(&eft, &cap);

        if (status != EFI_SUCCESS) {
                /* should never happen */
                printk(KERN_ERR "efitime: can't read time\n");
                return -EINVAL;
        }

        convert_from_efi_time(&eft, tm);

        return rtc_valid_tm(tm);
}

static int efi_set_time(struct device *dev, struct rtc_time *tm)
{
        efi_status_t status;
        efi_time_t eft;

        convert_to_efi_time(tm, &eft);

        status = efi.set_time(&eft);

        return status == EFI_SUCCESS ? 0 : -EINVAL;
}

static const struct rtc_class_ops efi_rtc_ops = {
        .read_time = efi_read_time,
        .set_time = efi_set_time,
        .read_alarm = efi_read_alarm,
        .set_alarm = efi_set_alarm,
};

static int __init efi_rtc_probe(struct platform_device *dev)
{
        struct rtc_device *rtc;

        rtc = rtc_device_register("rtc-efi", &dev->dev, &efi_rtc_ops,
                                        THIS_MODULE);
        if (IS_ERR(rtc))
                return PTR_ERR(rtc);

        platform_set_drvdata(dev, rtc);

        return 0;
}

static int __exit efi_rtc_remove(struct platform_device *dev)
{
        struct rtc_device *rtc = platform_get_drvdata(dev);

        rtc_device_unregister(rtc);

        return 0;
}

static struct platform_driver efi_rtc_driver = {
        .driver = {
                .name = "rtc-efi",
                .owner = THIS_MODULE,
        },
        .probe = efi_rtc_probe,
        .remove = __exit_p(efi_rtc_remove),
};

static int __init efi_rtc_init(void)
{
        return platform_driver_probe(&efi_rtc_driver, efi_rtc_probe);
}

static void __exit efi_rtc_exit(void)
{
        platform_driver_unregister(&efi_rtc_driver);
}

module_init(efi_rtc_init);
module_exit(efi_rtc_exit);

MODULE_AUTHOR("dann frazier <dannf@hp.com>");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("EFI RTC driver");