drivers/pps/kapi.c

   1 /*
   2  * kernel API
   3  *
   4  *
   5  * Copyright (C) 2005-2009   Rodolfo Giometti <giometti@linux.it>
   6  *
   7  *   This program is free software; you can redistribute it and/or modify
   8  *   it under the terms of the GNU General Public License as published by
   9  *   the Free Software Foundation; either version 2 of the License, or
  10  *   (at your option) any later version.
  11  *
  12  *   This program is distributed in the hope that it will be useful,
  13  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  *   GNU General Public License for more details.
  16  *
  17  *   You should have received a copy of the GNU General Public License
  18  *   along with this program; if not, write to the Free Software
  19  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20  */
  21
  22
  23 #include <linux/kernel.h>
  24 #include <linux/module.h>
  25 #include <linux/init.h>
  26 #include <linux/sched.h>
  27 #include <linux/time.h>
  28 #include <linux/spinlock.h>
  29 #include <linux/idr.h>
  30 #include <linux/fs.h>
  31 #include <linux/pps_kernel.h>
  32
  33 /*
  34  * Global variables
  35  */
  36
  37 DEFINE_SPINLOCK(pps_idr_lock);
  38 DEFINE_IDR(pps_idr);
  39
  40 /*
  41  * Local functions
  42  */
  43
  44 static void pps_add_offset(struct pps_ktime *ts, struct pps_ktime *offset)
  45 {
  46         ts->nsec += offset->nsec;
  47         while (ts->nsec >= NSEC_PER_SEC) {
  48                 ts->nsec -= NSEC_PER_SEC;
  49                 ts->sec++;
  50         }
  51         while (ts->nsec < 0) {
  52                 ts->nsec += NSEC_PER_SEC;
  53                 ts->sec--;
  54         }
  55         ts->sec += offset->sec;
  56 }
  57
  58 /*
  59  * Exported functions
  60  */
  61
  62 /* pps_get_source - find a PPS source
  63  * @source: the PPS source ID.
  64  *
  65  * This function is used to find an already registered PPS source into the
  66  * system.
  67  *
  68  * The function returns NULL if found nothing, otherwise it returns a pointer
  69  * to the PPS source data struct (the refcounter is incremented by 1).
  70  */
  71
  72 struct pps_device *pps_get_source(int source)
  73 {
  74         struct pps_device *pps;
  75         unsigned long flags;
  76
  77         spin_lock_irqsave(&pps_idr_lock, flags);
  78
  79         pps = idr_find(&pps_idr, source);
  80         if (pps != NULL)
  81                 atomic_inc(&pps->usage);
  82
  83         spin_unlock_irqrestore(&pps_idr_lock, flags);
  84
  85         return pps;
  86 }
  87
  88 /* pps_put_source - free the PPS source data
  89  * @pps: a pointer to the PPS source.
  90  *
  91  * This function is used to free a PPS data struct if its refcount is 0.
  92  */
  93
  94 void pps_put_source(struct pps_device *pps)
  95 {
  96         unsigned long flags;
  97
  98         spin_lock_irqsave(&pps_idr_lock, flags);
  99         BUG_ON(atomic_read(&pps->usage) == 0);
 100
 101         if (!atomic_dec_and_test(&pps->usage)) {
 102                 pps = NULL;
 103                 goto exit;
 104         }
 105
 106         /* No more reference to the PPS source. We can safely remove the
 107          * PPS data struct.
 108          */
 109         idr_remove(&pps_idr, pps->id);
 110
 111 exit:
 112         spin_unlock_irqrestore(&pps_idr_lock, flags);
 113         kfree(pps);
 114 }
 115
 116 /* pps_register_source - add a PPS source in the system
 117  * @info: the PPS info struct
 118  * @default_params: the default PPS parameters of the new source
 119  *
 120  * This function is used to add a new PPS source in the system. The new
 121  * source is described by info's fields and it will have, as default PPS
 122  * parameters, the ones specified into default_params.
 123  *
 124  * The function returns, in case of success, the PPS source ID.
 125  */
 126
 127 int pps_register_source(struct pps_source_info *info, int default_params)
 128 {
 129         struct pps_device *pps;
 130         int id;
 131         int err;
 132
 133         /* Sanity checks */
 134         if ((info->mode & default_params) != default_params) {
 135                 printk(KERN_ERR "pps: %s: unsupported default parameters\n",
 136                                         info->name);
 137                 err = -EINVAL;
 138                 goto pps_register_source_exit;
 139         }
 140         if ((info->mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)) != 0 &&
 141                         info->echo == NULL) {
 142                 printk(KERN_ERR "pps: %s: echo function is not defined\n",
 143                                         info->name);
 144                 err = -EINVAL;
 145                 goto pps_register_source_exit;
 146         }
 147         if ((info->mode & (PPS_TSFMT_TSPEC | PPS_TSFMT_NTPFP)) == 0) {
 148                 printk(KERN_ERR "pps: %s: unspecified time format\n",
 149                                         info->name);
 150                 err = -EINVAL;
 151                 goto pps_register_source_exit;
 152         }
 153
 154         /* Allocate memory for the new PPS source struct */
 155         pps = kzalloc(sizeof(struct pps_device), GFP_KERNEL);
 156         if (pps == NULL) {
 157                 err = -ENOMEM;
 158                 goto pps_register_source_exit;
 159         }
 160
 161         /* These initializations must be done before calling idr_get_new()
 162          * in order to avoid reces into pps_event().
 163          */
 164         pps->params.api_version = PPS_API_VERS;
 165         pps->params.mode = default_params;
 166         pps->info = *info;
 167
 168         init_waitqueue_head(&pps->queue);
 169         spin_lock_init(&pps->lock);
 170         atomic_set(&pps->usage, 1);
 171
 172         /* Get new ID for the new PPS source */
 173         if (idr_pre_get(&pps_idr, GFP_KERNEL) == 0) {
 174                 err = -ENOMEM;
 175                 goto kfree_pps;
 176         }
 177
 178         spin_lock_irq(&pps_idr_lock);
 179
 180         /* Now really allocate the PPS source.
 181          * After idr_get_new() calling the new source will be freely available
 182          * into the kernel.
 183          */
 184         err = idr_get_new(&pps_idr, pps, &id);
 185         if (err < 0) {
 186                 spin_unlock_irq(&pps_idr_lock);
 187                 goto kfree_pps;
 188         }
 189
 190         id = id & MAX_ID_MASK;
 191         if (id >= PPS_MAX_SOURCES) {
 192                 spin_unlock_irq(&pps_idr_lock);
 193
 194                 printk(KERN_ERR "pps: %s: too many PPS sources in the system\n",
 195                                         info->name);
 196                 err = -EBUSY;
 197                 goto free_idr;
 198         }
 199         pps->id = id;
 200
 201         spin_unlock_irq(&pps_idr_lock);
 202
 203         /* Create the char device */
 204         err = pps_register_cdev(pps);
 205         if (err < 0) {
 206                 printk(KERN_ERR "pps: %s: unable to create char device\n",
 207                                         info->name);
 208                 goto free_idr;
 209         }
 210
 211         pr_info("new PPS source %s at ID %d\n", info->name, id);
 212
 213         return id;
 214
 215 free_idr:
 216         spin_lock_irq(&pps_idr_lock);
 217         idr_remove(&pps_idr, id);
 218         spin_unlock_irq(&pps_idr_lock);
 219
 220 kfree_pps:
 221         kfree(pps);
 222
 223 pps_register_source_exit:
 224         printk(KERN_ERR "pps: %s: unable to register source\n", info->name);
 225
 226         return err;
 227 }
 228 EXPORT_SYMBOL(pps_register_source);
 229
 230 /* pps_unregister_source - remove a PPS source from the system
 231  * @source: the PPS source ID
 232  *
 233  * This function is used to remove a previously registered PPS source from
 234  * the system.
 235  */
 236
 237 void pps_unregister_source(int source)
 238 {
 239         struct pps_device *pps;
 240
 241         spin_lock_irq(&pps_idr_lock);
 242         pps = idr_find(&pps_idr, source);
 243
 244         if (!pps) {
 245                 BUG();
 246                 spin_unlock_irq(&pps_idr_lock);
 247                 return;
 248         }
 249         spin_unlock_irq(&pps_idr_lock);
 250
 251         pps_unregister_cdev(pps);
 252         pps_put_source(pps);
 253 }
 254 EXPORT_SYMBOL(pps_unregister_source);
 255
 256 /* pps_event - register a PPS event into the system
 257  * @source: the PPS source ID
 258  * @ts: the event timestamp
 259  * @event: the event type
 260  * @data: userdef pointer
 261  *
 262  * This function is used by each PPS client in order to register a new
 263  * PPS event into the system (it's usually called inside an IRQ handler).
 264  *
 265  * If an echo function is associated with the PPS source it will be called
 266  * as:
 267  *      pps->info.echo(source, event, data);
 268  */
 269
 270 void pps_event(int source, struct pps_ktime *ts, int event, void *data)
 271 {
 272         struct pps_device *pps;
 273         unsigned long flags;
 274
 275         if ((event & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR)) == 0) {
 276                 printk(KERN_ERR "pps: unknown event (%x) for source %d\n",
 277                         event, source);
 278                 return;
 279         }
 280
 281         pps = pps_get_source(source);
 282         if (!pps)
 283                 return;
 284
 285         pr_debug("PPS event on source %d at %llu.%06u\n",
 286                         pps->id, (unsigned long long) ts->sec, ts->nsec);
 287
 288         spin_lock_irqsave(&pps->lock, flags);
 289
 290         /* Must call the echo function? */
 291         if ((pps->params.mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)))
 292                 pps->info.echo(source, event, data);
 293
 294         /* Check the event */
 295         pps->current_mode = pps->params.mode;
 296         if (event & PPS_CAPTUREASSERT) {
 297                 /* We have to add an offset? */
 298                 if (pps->params.mode & PPS_OFFSETASSERT)
 299                         pps_add_offset(ts, &pps->params.assert_off_tu);
 300
 301                 /* Save the time stamp */
 302                 pps->assert_tu = *ts;
 303                 pps->assert_sequence++;
 304                 pr_debug("capture assert seq #%u for source %d\n",
 305                         pps->assert_sequence, source);
 306         }
 307         if (event & PPS_CAPTURECLEAR) {
 308                 /* We have to add an offset? */
 309                 if (pps->params.mode & PPS_OFFSETCLEAR)
 310                         pps_add_offset(ts, &pps->params.clear_off_tu);
 311
 312                 /* Save the time stamp */
 313                 pps->clear_tu = *ts;
 314                 pps->clear_sequence++;
 315                 pr_debug("capture clear seq #%u for source %d\n",
 316                         pps->clear_sequence, source);
 317         }
 318
 319         pps->go = ~0;
 320         wake_up_interruptible(&pps->queue);
 321
 322         kill_fasync(&pps->async_queue, SIGIO, POLL_IN);
 323
 324         spin_unlock_irqrestore(&pps->lock, flags);
 325
 326         /* Now we can release the PPS source for (possible) deregistration */
 327         pps_put_source(pps);
 328 }
 329 EXPORT_SYMBOL(pps_event);