1 /**************************************************************************/
2 /* File: read.c - read system call support for receiving CAN messages */
4 /* LinCAN - (Not only) Linux CAN bus driver */
5 /* Copyright (C) 2002-2009 DCE FEE CTU Prague <http://dce.felk.cvut.cz> */
6 /* Copyright (C) 2002-2009 Pavel Pisa <pisa@cmp.felk.cvut.cz> */
7 /* Funded by OCERA and FRESCOR IST projects */
8 /* Based on CAN driver code by Arnaud Westenberg <arnaud@wanadoo.nl> */
10 /* LinCAN is free software; you can redistribute it and/or modify it */
11 /* under terms of the GNU General Public License as published by the */
12 /* Free Software Foundation; either version 2, or (at your option) any */
13 /* later version. LinCAN is distributed in the hope that it will be */
14 /* useful, but WITHOUT ANY WARRANTY; without even the implied warranty */
15 /* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU */
16 /* General Public License for more details. You should have received a */
17 /* copy of the GNU General Public License along with LinCAN; see file */
18 /* COPYING. If not, write to the Free Software Foundation, 675 Mass Ave, */
19 /* Cambridge, MA 02139, USA. */
21 /* To allow use of LinCAN in the compact embedded systems firmware */
22 /* and RT-executives (RTEMS for example), main authors agree with next */
23 /* special exception: */
25 /* Including LinCAN header files in a file, instantiating LinCAN generics */
26 /* or templates, or linking other files with LinCAN objects to produce */
27 /* an application image/executable, does not by itself cause the */
28 /* resulting application image/executable to be covered by */
29 /* the GNU General Public License. */
30 /* This exception does not however invalidate any other reasons */
31 /* why the executable file might be covered by the GNU Public License. */
32 /* Publication of enhanced or derived LinCAN files is required although. */
33 /**************************************************************************/
35 #include "../include/can.h"
36 #include "../include/can_sysdep.h"
37 #include "../include/main.h"
38 #include "../include/read.h"
40 /* This is the 'Normal' read handler for normal transmission messages */
41 ssize_t can_read(struct file *file, char *buffer, size_t length, loff_t *offset)
43 struct canuser_t *canuser = (struct canuser_t*)(file->private_data);
44 struct canque_ends_t *qends;
46 struct canque_edge_t *qedge;
47 struct canque_slot_t *slot;
50 if(!canuser || (canuser->magic != CAN_USER_MAGIC)){
51 CANMSG("can_read: bad canuser magic\n");
55 if (length < sizeof(struct canmsg_t)) {
56 DEBUGMSG("Trying to read less bytes than a CAN message, \n");
57 DEBUGMSG("this will always return zero.\n");
61 qends = canuser->qends;
63 ret=canque_test_outslot(qends, &qedge, &slot);
65 if (file->f_flags & O_NONBLOCK) {
68 ret=canque_get_outslot_wait_kern(qends, &qedge, &slot);
70 if (signal_pending(current)) {
71 DEBUGMSG("Rx interrupted\n");
75 DEBUGMSG("no data received\n");
82 ret = copy_to_user(buffer, &slot->msg, sizeof(struct canmsg_t));
83 canque_free_outslot(qends, qedge, slot);
84 buffer += sizeof(struct canmsg_t);
85 bytes_to_copy = length-sizeof(struct canmsg_t);
86 if(ret) return -EFAULT;
88 while (bytes_to_copy > 0) {
89 ret=canque_test_outslot(qends, &qedge, &slot);
92 ret = copy_to_user(buffer, &slot->msg, sizeof(struct canmsg_t));
93 canque_free_outslot(qends, qedge, slot);
94 buffer += sizeof(struct canmsg_t);
95 bytes_to_copy -= sizeof(struct canmsg_t);
96 if(ret) return -EFAULT;
99 return length-bytes_to_copy;