Simple read byte data compilation problem

* Simple read byte data compilation problem
@ 2008-10-21  9:44 Fabien Marteau
       [not found] ` <ce62e9d00810210244p3194a50fj3b6b19209465ac7e-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
  0 siblings, 1 reply; 3+ messages in thread
From: Fabien Marteau @ 2008-10-21  9:44 UTC (permalink / raw)
  To: i2c-GZX6beZjE8VD60Wz+7aTrA

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Hy,

I wrote a simple user program to test an i2c bus driver. I found in
Documentation/i2c/dev-interface their is macro function to read data
(i2c_smbus_read_byte_data). I used it but I have link error when I compile :
$ arm-linux-gcc -O i2cread.c -o i2cread
/tmp/ccfa90st.o: In function `read_byte':
i2cread.c:(.text+0x3c): undefined reference to `i2c_smbus_read_byte_data'
collect2: ld returned 1 exit status

Is someone know what is the problem ?

Thanks in advance
FabM

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/* a simple program to read on i2c bus
 * Fabien Marteau <fabien.marteau@armadeus.com>
 *
 * inspired from : 
 *   ch7024: manage the Svideo controller CH7024
 *  author: thom25@users.sourceforge.net
 *
 *
 **  THE ARMADEUS PROJECT
 **
 **  Copyright (C) year  The source forge armadeus project team
 **
 ** This program is free software; you can redistribute it and/or modify
 ** it under the terms of the GNU General Public License as published by
 ** the Free Software Foundation; either version 2 of the License, or
 ** (at your option) any later version.
 ** 
 ** This program is distributed in the hope that it will be useful,
 ** but WITHOUT ANY WARRANTY; without even the implied warranty of
 ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 ** GNU General Public License for more details.
 ** 
 ** You should have received a copy of the GNU General Public License
 ** along with this program; if not, write to the Free Software 
 ** Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 **
 */
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>

#include <linux/i2c.h> 
#include <linux/i2c-dev.h>

#include <sys/ioctl.h>

int fd;

/* Read a byte on the I2C bus
   This is done by writing the register address 
   we want to access and then by reading this register
     @param fd: file descriptor of the device
     @param reg: register to access
     @param buf: buffer used to store the result
     @return : -1 in case of error otherwise 0
 */
__s32 read_byte( int fd,unsigned char addr, unsigned char reg)
{ 
	int err;
	__s32 res;
	/* select address */
	if(err=ioctl(fd,I2C_SLAVE,addr) < 0){
		perror("can't select this address\n");
		return err;
	}
	res = i2c_smbus_read_byte_data(fd,(__u8)reg);
	if(res<0)
		perror("read byte data error\n");
	return res;
}

/* i2cread i2c-devfile addr*/
int main(int argc, char **argv){
  unsigned char buf;
  unsigned char addr;
  unsigned char subaddr;
  unsigned char value;

  if(argc != 4){
    printf("wrong args numbers\nsyntaxe (hexa) :\n");
	printf("i2cread i2c-devfile addr subaddr\n");
    return -1;
  }

  fd = open(argv[1],O_RDWR);
  if(fd < 0){
    printf("%d : can't open %s\n",fd,argv[1]);
    return -1;
  }
  /* select address */
  addr =    (unsigned char )strtol(argv[2], (char **)NULL, 16);
  /* select subaddress */
  subaddr =    (unsigned char )strtol(argv[3], (char **)NULL, 16);

  buf = (unsigned char)read_byte(fd,addr, subaddr); 

  printf("Read component %02x at subaddress %02x->%02x\n",addr,subaddr,buf);

  return value;
}

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