drivers/w1/w1_family.c

   1 /*
   2  *      w1_family.c
   3  *
   4  * Copyright (c) 2004 Evgeniy Polyakov <johnpol@2ka.mipt.ru>
   5  *
   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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  20  */
  21
  22 #include <linux/spinlock.h>
  23 #include <linux/list.h>
  24 #include <linux/delay.h>
  25
  26 #include "w1_family.h"
  27
  28 DEFINE_SPINLOCK(w1_flock);
  29 static LIST_HEAD(w1_families);
  30
  31 static int w1_check_family(struct w1_family *f)
  32 {
  33         if (!f->fops->rname || !f->fops->rbin || !f->fops->rval || !f->fops->rvalname)
  34                 return -EINVAL;
  35
  36         return 0;
  37 }
  38
  39 int w1_register_family(struct w1_family *newf)
  40 {
  41         struct list_head *ent, *n;
  42         struct w1_family *f;
  43         int ret = 0;
  44
  45         if (w1_check_family(newf))
  46                 return -EINVAL;
  47
  48         spin_lock(&w1_flock);
  49         list_for_each_safe(ent, n, &w1_families) {
  50                 f = list_entry(ent, struct w1_family, family_entry);
  51
  52                 if (f->fid == newf->fid) {
  53                         ret = -EEXIST;
  54                         break;
  55                 }
  56         }
  57
  58         if (!ret) {
  59                 atomic_set(&newf->refcnt, 0);
  60                 newf->need_exit = 0;
  61                 list_add_tail(&newf->family_entry, &w1_families);
  62         }
  63
  64         spin_unlock(&w1_flock);
  65
  66         return ret;
  67 }
  68
  69 void w1_unregister_family(struct w1_family *fent)
  70 {
  71         struct list_head *ent, *n;
  72         struct w1_family *f;
  73
  74         spin_lock(&w1_flock);
  75         list_for_each_safe(ent, n, &w1_families) {
  76                 f = list_entry(ent, struct w1_family, family_entry);
  77
  78                 if (f->fid == fent->fid) {
  79                         list_del(&fent->family_entry);
  80                         break;
  81                 }
  82         }
  83
  84         fent->need_exit = 1;
  85
  86         spin_unlock(&w1_flock);
  87
  88         while (atomic_read(&fent->refcnt)) {
  89                 printk(KERN_INFO "Waiting for family %u to become free: refcnt=%d.\n",
  90                                 fent->fid, atomic_read(&fent->refcnt));
  91
  92                 if (msleep_interruptible(1000))
  93                         flush_signals(current);
  94         }
  95 }
  96
  97 /*
  98  * Should be called under w1_flock held.
  99  */
 100 struct w1_family * w1_family_registered(u8 fid)
 101 {
 102         struct list_head *ent, *n;
 103         struct w1_family *f = NULL;
 104         int ret = 0;
 105
 106         list_for_each_safe(ent, n, &w1_families) {
 107                 f = list_entry(ent, struct w1_family, family_entry);
 108
 109                 if (f->fid == fid) {
 110                         ret = 1;
 111                         break;
 112                 }
 113         }
 114
 115         return (ret) ? f : NULL;
 116 }
 117
 118 void w1_family_put(struct w1_family *f)
 119 {
 120         spin_lock(&w1_flock);
 121         __w1_family_put(f);
 122         spin_unlock(&w1_flock);
 123 }
 124
 125 void __w1_family_put(struct w1_family *f)
 126 {
 127         if (atomic_dec_and_test(&f->refcnt))
 128                 f->need_exit = 1;
 129 }
 130
 131 void w1_family_get(struct w1_family *f)
 132 {
 133         spin_lock(&w1_flock);
 134         __w1_family_get(f);
 135         spin_unlock(&w1_flock);
 136
 137 }
 138
 139 void __w1_family_get(struct w1_family *f)
 140 {
 141         smp_mb__before_atomic_inc();
 142         atomic_inc(&f->refcnt);
 143         smp_mb__after_atomic_inc();
 144 }
 145
 146 EXPORT_SYMBOL(w1_family_get);
 147 EXPORT_SYMBOL(w1_family_put);
 148 EXPORT_SYMBOL(w1_family_registered);
 149 EXPORT_SYMBOL(w1_unregister_family);
 150 EXPORT_SYMBOL(w1_register_family);