text: // SPDX-License-Identifier: GPL-2.0
  /*
   * RTC subsystem, sysfs interface
   *
   * Copyright (C) 2005 Tower Technologies
   * Author: Alessandro Zummo <a.zummo@towertech.it>
   */
  
  #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 sprintf(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 sprintf(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 sprintf(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 == 0) {
  		time64_t time;
  
  		time = rtc_tm_to_time64(&tm);
  		retval = sprintf(buf, "%lld\n", time);
  	}
  
  	return retval;
  }
  static DEVICE_ATTR_RO(since_epoch);
  
  static ssize_t
  max_user_freq_show(struct device *dev, struct device_attribute *attr, char *buf)
  {
  	return sprintf(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);
  
  /**
   * rtc_sysfs_show_hctosys - 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 sprintf(buf, "1\n");
  #endif
  	return sprintf(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;
  	time64_t 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) {
  		alarm = rtc_tm_to_time64(&alm.time);
  		retval = sprintf(buf, "%lld\n", alarm);
  	}
  
  	return retval;
  }
  
  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 == 0)
  		retval = sprintf(buf, "%ld\n", offset);
  
  	return retval;
  }
  
  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 sprintf(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 rtc->ops->set_alarm != NULL;
  }
  
  static umode_t rtc_attr_is_visible(struct kobject *kobj,
  				   struct attribute *attr, int n)
  {
  	struct device *dev = container_of(kobj, struct device, 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,
  };
  
  static const struct attribute_group *rtc_attr_groups[] = {
  	&rtc_attr_group,
  	NULL
  };
  
  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 (rtc->registered)
  		return -EINVAL;
  	if (!grps)
  		return -EINVAL;
  
  	groups = rtc->dev.groups;
  	if (groups)
  		for (; *groups; groups++)
  			old_cnt++;
  
  	for (groups = grps; *groups; groups++)
  		add_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);
  