/*
   * 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.
   *
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #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) {
  		pr_err("EFI year < 1998, invalid date
  ");
  		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);
  
  	dev_warn(dev, "write status is %d
  ", (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 */
  		dev_err(dev, "can't read time
  ");
  		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 = devm_rtc_device_register(&dev->dev, "rtc-efi", &efi_rtc_ops,
  					THIS_MODULE);
  	if (IS_ERR(rtc))
  		return PTR_ERR(rtc);
  
  	platform_set_drvdata(dev, rtc);
  
  	return 0;
  }
  
  static struct platform_driver efi_rtc_driver = {
  	.driver = {
  		.name = "rtc-efi",
  		.owner = THIS_MODULE,
  	},
  };
  
  module_platform_driver_probe(efi_rtc_driver, efi_rtc_probe);
  
  MODULE_AUTHOR("dann frazier <dannf@hp.com>");
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("EFI RTC driver");