drivers/pps/kc.c

   1 /*
   2  * PPS kernel consumer API
   3  *
   4  * Copyright (C) 2009-2010   Alexander Gordeev <lasaine@lvk.cs.msu.su>
   5  *
   6  *   This program is free software; you can redistribute it and/or modify
   7  *   it under the terms of the GNU General Public License as published by
   8  *   the Free Software Foundation; either version 2 of the License, or
   9  *   (at your option) any later version.
  10  *
  11  *   This program is distributed in the hope that it will be useful,
  12  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *   GNU General Public License for more details.
  15  *
  16  *   You should have received a copy of the GNU General Public License
  17  *   along with this program; if not, write to the Free Software
  18  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19  */
  20
  21 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  22
  23 #include <linux/kernel.h>
  24 #include <linux/module.h>
  25 #include <linux/device.h>
  26 #include <linux/init.h>
  27 #include <linux/spinlock.h>
  28 #include <linux/pps_kernel.h>
  29
  30 #include "kc.h"
  31
  32 /*
  33  * Global variables
  34  */
  35
  36 /* state variables to bind kernel consumer */
  37 static DEFINE_SPINLOCK(pps_kc_hardpps_lock);
  38 /* PPS API (RFC 2783): current source and mode for kernel consumer */
  39 static struct pps_device *pps_kc_hardpps_dev;   /* unique pointer to device */
  40 static int pps_kc_hardpps_mode;         /* mode bits for kernel consumer */
  41
  42 /* pps_kc_bind - control PPS kernel consumer binding
  43  * @pps: the PPS source
  44  * @bind_args: kernel consumer bind parameters
  45  *
  46  * This function is used to bind or unbind PPS kernel consumer according to
  47  * supplied parameters. Should not be called in interrupt context.
  48  */
  49 int pps_kc_bind(struct pps_device *pps, struct pps_bind_args *bind_args)
  50 {
  51         /* Check if another consumer is already bound */
  52         spin_lock_irq(&pps_kc_hardpps_lock);
  53
  54         if (bind_args->edge == 0)
  55                 if (pps_kc_hardpps_dev == pps) {
  56                         pps_kc_hardpps_mode = 0;
  57                         pps_kc_hardpps_dev = NULL;
  58                         spin_unlock_irq(&pps_kc_hardpps_lock);
  59                         dev_info(pps->dev, "unbound kernel"
  60                                         " consumer\n");
  61                 } else {
  62                         spin_unlock_irq(&pps_kc_hardpps_lock);
  63                         dev_err(pps->dev, "selected kernel consumer"
  64                                         " is not bound\n");
  65                         return -EINVAL;
  66                 }
  67         else
  68                 if (pps_kc_hardpps_dev == NULL ||
  69                                 pps_kc_hardpps_dev == pps) {
  70                         pps_kc_hardpps_mode = bind_args->edge;
  71                         pps_kc_hardpps_dev = pps;
  72                         spin_unlock_irq(&pps_kc_hardpps_lock);
  73                         dev_info(pps->dev, "bound kernel consumer: "
  74                                 "edge=0x%x\n", bind_args->edge);
  75                 } else {
  76                         spin_unlock_irq(&pps_kc_hardpps_lock);
  77                         dev_err(pps->dev, "another kernel consumer"
  78                                         " is already bound\n");
  79                         return -EINVAL;
  80                 }
  81
  82         return 0;
  83 }
  84
  85 /* pps_kc_remove - unbind kernel consumer on PPS source removal
  86  * @pps: the PPS source
  87  *
  88  * This function is used to disable kernel consumer on PPS source removal
  89  * if this source was bound to PPS kernel consumer. Can be called on any
  90  * source safely. Should not be called in interrupt context.
  91  */
  92 void pps_kc_remove(struct pps_device *pps)
  93 {
  94         spin_lock_irq(&pps_kc_hardpps_lock);
  95         if (pps == pps_kc_hardpps_dev) {
  96                 pps_kc_hardpps_mode = 0;
  97                 pps_kc_hardpps_dev = NULL;
  98                 spin_unlock_irq(&pps_kc_hardpps_lock);
  99                 dev_info(pps->dev, "unbound kernel consumer"
 100                                 " on device removal\n");
 101         } else
 102                 spin_unlock_irq(&pps_kc_hardpps_lock);
 103 }
 104
 105 /* pps_kc_event - call hardpps() on PPS event
 106  * @pps: the PPS source
 107  * @ts: PPS event timestamp
 108  * @event: PPS event edge
 109  *
 110  * This function calls hardpps() when an event from bound PPS source occurs.
 111  */
 112 void pps_kc_event(struct pps_device *pps, struct pps_event_time *ts,
 113                 int event)
 114 {
 115         unsigned long flags;
 116
 117         /* Pass some events to kernel consumer if activated */
 118         spin_lock_irqsave(&pps_kc_hardpps_lock, flags);
 119         if (pps == pps_kc_hardpps_dev && event & pps_kc_hardpps_mode)
 120                 hardpps(&ts->ts_real, &ts->ts_raw);
 121         spin_unlock_irqrestore(&pps_kc_hardpps_lock, flags);
 122 }