lincan/src/read.c

   1 /* read.c
   2  * Linux CAN-bus device driver.
   3  * Written by Arnaud Westenberg email:arnaud@wanadoo.nl
   4  * Rewritten for new CAN queues by Pavel Pisa - OCERA team member
   5  * email:pisa@cmp.felk.cvut.cz
   6  * This software is released under the GPL-License.
   7  * Version lincan-0.3  17 Jun 2004
   8  */
   9
  10 #include "../include/can.h"
  11 #include "../include/can_sysdep.h"
  12 #include "../include/main.h"
  13 #include "../include/read.h"
  14
  15 /* This is the 'Normal' read handler for normal transmission messages */
  16 ssize_t can_read(struct file *file, char *buffer, size_t length, loff_t *offset)
  17 {
  18         struct canuser_t *canuser = (struct canuser_t*)(file->private_data);
  19         struct canque_ends_t *qends;
  20         int bytes_to_copy;
  21         struct canque_edge_t *qedge;
  22         struct canque_slot_t *slot;
  23         int ret;
  24
  25         if(!canuser || (canuser->magic != CAN_USER_MAGIC)){
  26                 CANMSG("can_read: bad canuser magic\n");
  27                 return -ENODEV;
  28         }
  29
  30         if (length < sizeof(struct canmsg_t)) {
  31                 DEBUGMSG("Trying to read less bytes than a CAN message, \n");
  32                 DEBUGMSG("this will always return zero.\n");
  33                 return 0;
  34         }
  35
  36         qends = canuser->qends;
  37
  38         ret=canque_test_outslot(qends, &qedge, &slot);
  39         if(ret<0){
  40                 if (file->f_flags & O_NONBLOCK) {
  41                         return -EAGAIN;
  42                 }
  43                 ret=canque_get_outslot_wait_kern(qends, &qedge, &slot);
  44                 if(ret<0){
  45                         if (signal_pending(current)) {
  46                                 DEBUGMSG("Rx interrupted\n");
  47                                 return -EINTR;
  48                         }
  49                         /*if (!can_timeout) {
  50                                 DEBUGMSG("no data received\n");
  51                                 return 0;
  52                         }*/
  53                         return -EIO;
  54                 }
  55         }
  56
  57         ret = copy_to_user(buffer, &slot->msg, sizeof(struct canmsg_t));
  58         canque_free_outslot(qends, qedge, slot);
  59         buffer += sizeof(struct canmsg_t);
  60         bytes_to_copy = length-sizeof(struct canmsg_t);
  61         if(ret) return -EFAULT;
  62
  63         while (bytes_to_copy > 0) {
  64                 ret=canque_test_outslot(qends, &qedge, &slot);
  65                 if(ret<0)
  66                         break;
  67                 ret = copy_to_user(buffer, &slot->msg, sizeof(struct canmsg_t));
  68                 canque_free_outslot(qends, qedge, slot);
  69                 buffer += sizeof(struct canmsg_t);
  70                 bytes_to_copy -= sizeof(struct canmsg_t);
  71                 if(ret) return -EFAULT;
  72         }
  73
  74         return length-bytes_to_copy;
  75 }
  76