drivers/isdn/mISDN/clock.c

   1 /*
   2  * Copyright 2008  by Andreas Eversberg <andreas@eversberg.eu>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  * Quick API description:
  14  *
  15  * A clock source registers using mISDN_register_clock:
  16  *      name = text string to name clock source
  17  *      priority = value to priorize clock sources (0 = default)
  18  *      ctl = callback function to enable/disable clock source
  19  *      priv = private pointer of clock source
  20  *      return = pointer to clock source structure;
  21  *
  22  * Note: Callback 'ctl' can be called before mISDN_register_clock returns!
  23  *       Also it can be called during mISDN_unregister_clock.
  24  *
  25  * A clock source calls mISDN_clock_update with given samples elapsed, if
  26  * enabled. If function call is delayed, tv must be set with the timestamp
  27  * of the actual event.
  28  *
  29  * A clock source unregisters using mISDN_unregister_clock.
  30  *
  31  * To get current clock, call mISDN_clock_get. The signed short value
  32  * counts the number of samples since. Time since last clock event is added.
  33  *
  34  */
  35
  36 #include <linux/types.h>
  37 #include <linux/stddef.h>
  38 #include <linux/spinlock.h>
  39 #include <linux/mISDNif.h>
  40 #include "core.h"
  41
  42 static u_int *debug;
  43 static LIST_HEAD(iclock_list);
  44 static DEFINE_RWLOCK(iclock_lock);
  45 static u16 iclock_count;                /* counter of last clock */
  46 static struct timeval iclock_tv;        /* time stamp of last clock */
  47 static int iclock_tv_valid;             /* already received one timestamp */
  48 static struct mISDNclock *iclock_current;
  49
  50 void
  51 mISDN_init_clock(u_int *dp)
  52 {
  53         debug = dp;
  54         do_gettimeofday(&iclock_tv);
  55 }
  56
  57 static void
  58 select_iclock(void)
  59 {
  60         struct mISDNclock *iclock, *bestclock = NULL, *lastclock = NULL;
  61         int pri = -128;
  62
  63         list_for_each_entry(iclock, &iclock_list, list) {
  64                 if (iclock->pri > pri) {
  65                         pri = iclock->pri;
  66                         bestclock = iclock;
  67                 }
  68                 if (iclock_current == iclock)
  69                         lastclock = iclock;
  70         }
  71         if (lastclock && bestclock != lastclock) {
  72                 /* last used clock source still exists but changes, disable */
  73                 if (*debug & DEBUG_CLOCK)
  74                         printk(KERN_DEBUG "Old clock source '%s' disable.\n",
  75                                 lastclock->name);
  76                 lastclock->ctl(lastclock->priv, 0);
  77         }
  78         if (bestclock && bestclock != iclock_current) {
  79                 /* new clock source selected, enable */
  80                 if (*debug & DEBUG_CLOCK)
  81                         printk(KERN_DEBUG "New clock source '%s' enable.\n",
  82                                 bestclock->name);
  83                 bestclock->ctl(bestclock->priv, 1);
  84         }
  85         if (bestclock != iclock_current) {
  86                 /* no clock received yet */
  87                 iclock_tv_valid = 0;
  88         }
  89         iclock_current = bestclock;
  90 }
  91
  92 struct mISDNclock
  93 *mISDN_register_clock(char *name, int pri, clockctl_func_t *ctl, void *priv)
  94 {
  95         u_long                  flags;
  96         struct mISDNclock       *iclock;
  97
  98         if (*debug & (DEBUG_CORE | DEBUG_CLOCK))
  99                 printk(KERN_DEBUG "%s: %s %d\n", __func__, name, pri);
 100         iclock = kzalloc(sizeof(struct mISDNclock), GFP_ATOMIC);
 101         if (!iclock) {
 102                 printk(KERN_ERR "%s: No memory for clock entry.\n", __func__);
 103                 return NULL;
 104         }
 105         strncpy(iclock->name, name, sizeof(iclock->name)-1);
 106         iclock->pri = pri;
 107         iclock->priv = priv;
 108         iclock->ctl = ctl;
 109         write_lock_irqsave(&iclock_lock, flags);
 110         list_add_tail(&iclock->list, &iclock_list);
 111         select_iclock();
 112         write_unlock_irqrestore(&iclock_lock, flags);
 113         return iclock;
 114 }
 115 EXPORT_SYMBOL(mISDN_register_clock);
 116
 117 void
 118 mISDN_unregister_clock(struct mISDNclock *iclock)
 119 {
 120         u_long  flags;
 121
 122         if (*debug & (DEBUG_CORE | DEBUG_CLOCK))
 123                 printk(KERN_DEBUG "%s: %s %d\n", __func__, iclock->name,
 124                         iclock->pri);
 125         write_lock_irqsave(&iclock_lock, flags);
 126         if (iclock_current == iclock) {
 127                 if (*debug & DEBUG_CLOCK)
 128                         printk(KERN_DEBUG
 129                                 "Current clock source '%s' unregisters.\n",
 130                                 iclock->name);
 131                 iclock->ctl(iclock->priv, 0);
 132         }
 133         list_del(&iclock->list);
 134         select_iclock();
 135         write_unlock_irqrestore(&iclock_lock, flags);
 136 }
 137 EXPORT_SYMBOL(mISDN_unregister_clock);
 138
 139 void
 140 mISDN_clock_update(struct mISDNclock *iclock, int samples, struct timeval *tv)
 141 {
 142         u_long          flags;
 143         struct timeval  tv_now;
 144         time_t          elapsed_sec;
 145         int             elapsed_8000th;
 146
 147         write_lock_irqsave(&iclock_lock, flags);
 148         if (iclock_current != iclock) {
 149                 printk(KERN_ERR "%s: '%s' sends us clock updates, but we do "
 150                         "listen to '%s'. This is a bug!\n", __func__,
 151                         iclock->name,
 152                         iclock_current ? iclock_current->name : "nothing");
 153                 iclock->ctl(iclock->priv, 0);
 154                 write_unlock_irqrestore(&iclock_lock, flags);
 155                 return;
 156         }
 157         if (iclock_tv_valid) {
 158                 /* increment sample counter by given samples */
 159                 iclock_count += samples;
 160                 if (tv) { /* tv must be set, if function call is delayed */
 161                         iclock_tv.tv_sec = tv->tv_sec;
 162                         iclock_tv.tv_usec = tv->tv_usec;
 163                 } else
 164                         do_gettimeofday(&iclock_tv);
 165         } else {
 166                 /* calc elapsed time by system clock */
 167                 if (tv) { /* tv must be set, if function call is delayed */
 168                         tv_now.tv_sec = tv->tv_sec;
 169                         tv_now.tv_usec = tv->tv_usec;
 170                 } else
 171                         do_gettimeofday(&tv_now);
 172                 elapsed_sec = tv_now.tv_sec - iclock_tv.tv_sec;
 173                 elapsed_8000th = (tv_now.tv_usec / 125)
 174                         - (iclock_tv.tv_usec / 125);
 175                 if (elapsed_8000th < 0) {
 176                         elapsed_sec -= 1;
 177                         elapsed_8000th += 8000;
 178                 }
 179                 /* add elapsed time to counter and set new timestamp */
 180                 iclock_count += elapsed_sec * 8000 + elapsed_8000th;
 181                 iclock_tv.tv_sec = tv_now.tv_sec;
 182                 iclock_tv.tv_usec = tv_now.tv_usec;
 183                 iclock_tv_valid = 1;
 184                 if (*debug & DEBUG_CLOCK)
 185                         printk("Received first clock from source '%s'.\n",
 186                             iclock_current ? iclock_current->name : "nothing");
 187         }
 188         write_unlock_irqrestore(&iclock_lock, flags);
 189 }
 190 EXPORT_SYMBOL(mISDN_clock_update);
 191
 192 unsigned short
 193 mISDN_clock_get(void)
 194 {
 195         u_long          flags;
 196         struct timeval  tv_now;
 197         time_t          elapsed_sec;
 198         int             elapsed_8000th;
 199         u16             count;
 200
 201         read_lock_irqsave(&iclock_lock, flags);
 202         /* calc elapsed time by system clock */
 203         do_gettimeofday(&tv_now);
 204         elapsed_sec = tv_now.tv_sec - iclock_tv.tv_sec;
 205         elapsed_8000th = (tv_now.tv_usec / 125) - (iclock_tv.tv_usec / 125);
 206         if (elapsed_8000th < 0) {
 207                 elapsed_sec -= 1;
 208                 elapsed_8000th += 8000;
 209         }
 210         /* add elapsed time to counter */
 211         count = iclock_count + elapsed_sec * 8000 + elapsed_8000th;
 212         read_unlock_irqrestore(&iclock_lock, flags);
 213         return count;
 214 }
 215 EXPORT_SYMBOL(mISDN_clock_get);
 216