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/slab.h>
  37 #include <linux/types.h>
  38 #include <linux/stddef.h>
  39 #include <linux/spinlock.h>
  40 #include <linux/mISDNif.h>
  41 #include <linux/export.h>
  42 #include "core.h"
  43
  44 static u_int *debug;
  45 static LIST_HEAD(iclock_list);
  46 static DEFINE_RWLOCK(iclock_lock);
  47 static u16 iclock_count;                /* counter of last clock */
  48 static struct timeval iclock_tv;        /* time stamp of last clock */
  49 static int iclock_tv_valid;             /* already received one timestamp */
  50 static struct mISDNclock *iclock_current;
  51
  52 void
  53 mISDN_init_clock(u_int *dp)
  54 {
  55         debug = dp;
  56         do_gettimeofday(&iclock_tv);
  57 }
  58
  59 static void
  60 select_iclock(void)
  61 {
  62         struct mISDNclock *iclock, *bestclock = NULL, *lastclock = NULL;
  63         int pri = -128;
  64
  65         list_for_each_entry(iclock, &iclock_list, list) {
  66                 if (iclock->pri > pri) {
  67                         pri = iclock->pri;
  68                         bestclock = iclock;
  69                 }
  70                 if (iclock_current == iclock)
  71                         lastclock = iclock;
  72         }
  73         if (lastclock && bestclock != lastclock) {
  74                 /* last used clock source still exists but changes, disable */
  75                 if (*debug & DEBUG_CLOCK)
  76                         printk(KERN_DEBUG "Old clock source '%s' disable.\n",
  77                                lastclock->name);
  78                 lastclock->ctl(lastclock->priv, 0);
  79         }
  80         if (bestclock && bestclock != iclock_current) {
  81                 /* new clock source selected, enable */
  82                 if (*debug & DEBUG_CLOCK)
  83                         printk(KERN_DEBUG "New clock source '%s' enable.\n",
  84                                bestclock->name);
  85                 bestclock->ctl(bestclock->priv, 1);
  86         }
  87         if (bestclock != iclock_current) {
  88                 /* no clock received yet */
  89                 iclock_tv_valid = 0;
  90         }
  91         iclock_current = bestclock;
  92 }
  93
  94 struct mISDNclock
  95 *mISDN_register_clock(char *name, int pri, clockctl_func_t *ctl, void *priv)
  96 {
  97         u_long                  flags;
  98         struct mISDNclock       *iclock;
  99
 100         if (*debug & (DEBUG_CORE | DEBUG_CLOCK))
 101                 printk(KERN_DEBUG "%s: %s %d\n", __func__, name, pri);
 102         iclock = kzalloc(sizeof(struct mISDNclock), GFP_ATOMIC);
 103         if (!iclock) {
 104                 printk(KERN_ERR "%s: No memory for clock entry.\n", __func__);
 105                 return NULL;
 106         }
 107         strncpy(iclock->name, name, sizeof(iclock->name) - 1);
 108         iclock->pri = pri;
 109         iclock->priv = priv;
 110         iclock->ctl = ctl;
 111         write_lock_irqsave(&iclock_lock, flags);
 112         list_add_tail(&iclock->list, &iclock_list);
 113         select_iclock();
 114         write_unlock_irqrestore(&iclock_lock, flags);
 115         return iclock;
 116 }
 117 EXPORT_SYMBOL(mISDN_register_clock);
 118
 119 void
 120 mISDN_unregister_clock(struct mISDNclock *iclock)
 121 {
 122         u_long  flags;
 123
 124         if (*debug & (DEBUG_CORE | DEBUG_CLOCK))
 125                 printk(KERN_DEBUG "%s: %s %d\n", __func__, iclock->name,
 126                        iclock->pri);
 127         write_lock_irqsave(&iclock_lock, flags);
 128         if (iclock_current == iclock) {
 129                 if (*debug & DEBUG_CLOCK)
 130                         printk(KERN_DEBUG
 131                                "Current clock source '%s' unregisters.\n",
 132                                iclock->name);
 133                 iclock->ctl(iclock->priv, 0);
 134         }
 135         list_del(&iclock->list);
 136         select_iclock();
 137         write_unlock_irqrestore(&iclock_lock, flags);
 138 }
 139 EXPORT_SYMBOL(mISDN_unregister_clock);
 140
 141 void
 142 mISDN_clock_update(struct mISDNclock *iclock, int samples, struct timeval *tv)
 143 {
 144         u_long          flags;
 145         struct timeval  tv_now;
 146         time_t          elapsed_sec;
 147         int             elapsed_8000th;
 148
 149         write_lock_irqsave(&iclock_lock, flags);
 150         if (iclock_current != iclock) {
 151                 printk(KERN_ERR "%s: '%s' sends us clock updates, but we do "
 152                        "listen to '%s'. This is a bug!\n", __func__,
 153                        iclock->name,
 154                        iclock_current ? iclock_current->name : "nothing");
 155                 iclock->ctl(iclock->priv, 0);
 156                 write_unlock_irqrestore(&iclock_lock, flags);
 157                 return;
 158         }
 159         if (iclock_tv_valid) {
 160                 /* increment sample counter by given samples */
 161                 iclock_count += samples;
 162                 if (tv) { /* tv must be set, if function call is delayed */
 163                         iclock_tv.tv_sec = tv->tv_sec;
 164                         iclock_tv.tv_usec = tv->tv_usec;
 165                 } else
 166                         do_gettimeofday(&iclock_tv);
 167         } else {
 168                 /* calc elapsed time by system clock */
 169                 if (tv) { /* tv must be set, if function call is delayed */
 170                         tv_now.tv_sec = tv->tv_sec;
 171                         tv_now.tv_usec = tv->tv_usec;
 172                 } else
 173                         do_gettimeofday(&tv_now);
 174                 elapsed_sec = tv_now.tv_sec - iclock_tv.tv_sec;
 175                 elapsed_8000th = (tv_now.tv_usec / 125)
 176                         - (iclock_tv.tv_usec / 125);
 177                 if (elapsed_8000th < 0) {
 178                         elapsed_sec -= 1;
 179                         elapsed_8000th += 8000;
 180                 }
 181                 /* add elapsed time to counter and set new timestamp */
 182                 iclock_count += elapsed_sec * 8000 + elapsed_8000th;
 183                 iclock_tv.tv_sec = tv_now.tv_sec;
 184                 iclock_tv.tv_usec = tv_now.tv_usec;
 185                 iclock_tv_valid = 1;
 186                 if (*debug & DEBUG_CLOCK)
 187                         printk("Received first clock from source '%s'.\n",
 188                                iclock_current ? iclock_current->name : "nothing");
 189         }
 190         write_unlock_irqrestore(&iclock_lock, flags);
 191 }
 192 EXPORT_SYMBOL(mISDN_clock_update);
 193
 194 unsigned short
 195 mISDN_clock_get(void)
 196 {
 197         u_long          flags;
 198         struct timeval  tv_now;
 199         time_t          elapsed_sec;
 200         int             elapsed_8000th;
 201         u16             count;
 202
 203         read_lock_irqsave(&iclock_lock, flags);
 204         /* calc elapsed time by system clock */
 205         do_gettimeofday(&tv_now);
 206         elapsed_sec = tv_now.tv_sec - iclock_tv.tv_sec;
 207         elapsed_8000th = (tv_now.tv_usec / 125) - (iclock_tv.tv_usec / 125);
 208         if (elapsed_8000th < 0) {
 209                 elapsed_sec -= 1;
 210                 elapsed_8000th += 8000;
 211         }
 212         /* add elapsed time to counter */
 213         count = iclock_count + elapsed_sec * 8000 + elapsed_8000th;
 214         read_unlock_irqrestore(&iclock_lock, flags);
 215         return count;
 216 }
 217 EXPORT_SYMBOL(mISDN_clock_get);