rtc-efi.c

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/*
 * rtc-efi: RTC Class Driver for EFI-based systems
 *
 * Copyright (C) 2009 Hewlett-Packard Development Company, L.P.
 *
 * Author: dann frazier <[email protected]>
 * 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,
    },
    .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 <[email protected]>");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("EFI RTC driver");