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   1 /**
   2  * @file medlock.c
   3  *
   4  * @brief Implements the device lock class.
   5  * @note Copyright (C) 2006 Meilhaus Electronic GmbH (support@meilhaus.de)
   6  * @author Guenter Gebhardt
   7  */
   8
   9 /*
  10  * Copyright (C) 2007 Meilhaus Electronic GmbH (support@meilhaus.de)
  11  *
  12  * This file is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 2 of the License, or
  15  * (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with this program; if not, write to the Free Software
  24  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  25  */
  26
  27 #include <linux/spinlock.h>
  28
  29 #include "medefines.h"
  30 #include "meerror.h"
  31
  32 #include "medebug.h"
  33 #include "meslist.h"
  34 #include "mesubdevice.h"
  35 #include "medlock.h"
  36
  37 int me_dlock_enter(struct me_dlock *dlock, struct file *filep)
  38 {
  39         PDEBUG_LOCKS("executed.\n");
  40
  41         spin_lock(&dlock->spin_lock);
  42
  43         if ((dlock->filep) != NULL && (dlock->filep != filep)) {
  44                 PERROR("Device is locked by another process.\n");
  45                 spin_unlock(&dlock->spin_lock);
  46                 return ME_ERRNO_LOCKED;
  47         }
  48
  49         dlock->count++;
  50
  51         spin_unlock(&dlock->spin_lock);
  52
  53         return ME_ERRNO_SUCCESS;
  54 }
  55
  56 int me_dlock_exit(struct me_dlock *dlock, struct file *filep)
  57 {
  58         PDEBUG_LOCKS("executed.\n");
  59
  60         spin_lock(&dlock->spin_lock);
  61         dlock->count--;
  62         spin_unlock(&dlock->spin_lock);
  63
  64         return ME_ERRNO_SUCCESS;
  65 }
  66
  67 int me_dlock_lock(struct me_dlock *dlock,
  68                   struct file *filep, int lock, int flags, me_slist_t *slist)
  69 {
  70         int err = ME_ERRNO_SUCCESS;
  71         int i;
  72         me_subdevice_t *subdevice;
  73
  74         PDEBUG_LOCKS("executed.\n");
  75
  76         spin_lock(&dlock->spin_lock);
  77
  78         switch (lock) {
  79
  80         case ME_LOCK_RELEASE:
  81                 if ((dlock->filep == filep) || (dlock->filep == NULL)) {
  82                         dlock->filep = NULL;
  83
  84                         /* Unlock all possibly locked subdevices. */
  85
  86                         for (i = 0; i < me_slist_get_number_subdevices(slist);
  87                              i++) {
  88                                 subdevice = me_slist_get_subdevice(slist, i);
  89
  90                                 if (subdevice)
  91                                         err =
  92                                             subdevice->
  93                                             me_subdevice_lock_subdevice
  94                                             (subdevice, filep, ME_LOCK_RELEASE,
  95                                              flags);
  96                                 else
  97                                         err = ME_ERRNO_INTERNAL;
  98                         }
  99                 }
 100
 101                 break;
 102
 103         case ME_LOCK_SET:
 104                 if (dlock->count) {
 105                         PERROR("Device is used by another process.\n");
 106                         err = ME_ERRNO_USED;
 107                 } else if ((dlock->filep != NULL) && (dlock->filep != filep)) {
 108                         PERROR("Device is locked by another process.\n");
 109                         err = ME_ERRNO_LOCKED;
 110                 } else if (dlock->filep == NULL) {
 111                         /* Check any subdevice is locked by another process. */
 112
 113                         for (i = 0; i < me_slist_get_number_subdevices(slist);
 114                              i++) {
 115                                 subdevice = me_slist_get_subdevice(slist, i);
 116
 117                                 if (subdevice) {
 118                                         if ((err =
 119                                              subdevice->
 120                                              me_subdevice_lock_subdevice
 121                                              (subdevice, filep, ME_LOCK_CHECK,
 122                                               flags))) {
 123                                                 PERROR
 124                                                     ("A subdevice is locked by another process.\n");
 125                                                 break;
 126                                         }
 127                                 } else {
 128                                         err = ME_ERRNO_INTERNAL;
 129                                 }
 130                         }
 131
 132                         /* If no subdevices are locked by other processes,
 133                            we can take ownership of the device. Otherwise we jump ahead. */
 134                         if (!err)
 135                                 dlock->filep = filep;
 136                 }
 137
 138                 break;
 139
 140         case ME_LOCK_CHECK:
 141                 if (dlock->count) {
 142                         err = ME_ERRNO_USED;
 143                 } else if ((dlock->filep != NULL) && (dlock->filep != filep)) {
 144                         err = ME_ERRNO_LOCKED;
 145                 } else if (dlock->filep == NULL) {
 146                         for (i = 0; i < me_slist_get_number_subdevices(slist);
 147                              i++) {
 148                                 subdevice = me_slist_get_subdevice(slist, i);
 149
 150                                 if (subdevice) {
 151                                         if ((err =
 152                                              subdevice->
 153                                              me_subdevice_lock_subdevice
 154                                              (subdevice, filep, ME_LOCK_CHECK,
 155                                               flags))) {
 156                                                 PERROR
 157                                                     ("A subdevice is locked by another process.\n");
 158                                                 break;
 159                                         }
 160                                 } else {
 161                                         err = ME_ERRNO_INTERNAL;
 162                                 }
 163                         }
 164                 }
 165
 166                 break;
 167
 168         default:
 169                 PERROR("Invalid lock.\n");
 170
 171                 err = ME_ERRNO_INVALID_LOCK;
 172
 173                 break;
 174         }
 175
 176         spin_unlock(&dlock->spin_lock);
 177
 178         return err;
 179 }
 180
 181 void me_dlock_deinit(struct me_dlock *dlock)
 182 {
 183         PDEBUG_LOCKS("executed.\n");
 184 }
 185
 186 int me_dlock_init(me_dlock_t *dlock)
 187 {
 188         PDEBUG_LOCKS("executed.\n");
 189
 190         dlock->filep = NULL;
 191         dlock->count = 0;
 192         spin_lock_init(&dlock->spin_lock);
 193
 194         return 0;
 195 }