IBASE SMARC-EVK1 - Manual (Page 66)

40 SMARC Evaluation Kit
6. Appendix A– I2C, GPIO, watchdog reference code Coding.
6.1. How to use I2C in Linux
Reading / writing i2c
i2cget.c
/*
i2cget.c - A user-space program to read an I2C register.
Copyright (C) 2005-2012 Jean Delvare <[email protected]>
Based on i2cset.c:
Copyright (C) 2001-2003 Frodo Looijaard <[email protected]>, and
Mark D. Studebaker <[email protected]>
Copyright (C) 2004-2005 Jean Delvare
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., 51 Franklin Street, Fifth Floor, Boston,
MA 02110-1301 USA.
*/
#include <sys/ioctl.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <linux/i2c-dev.h>
#include "i2cbusses.h"
#include "util.h"
#include "../version.h"
static void help(void) __attribute__ ((noreturn));
static void help(void)
{
fprintf(stderr,
"Usage: i2cget [-f] [-y] I2CBUS CHIP-ADDRESS [DATA-ADDRESS [MODE]]\n"
" I2CBUS is an integer or an I2C bus name\n"
" ADDRESS is an integer (0x03 - 0x77)\n"
" MODE is one of:\n"
" b (read byte data, default)\n"
" w (read word data)\n"
" c (write byte/read byte)\n"
" Append p for SMBus PEC\n");
exit(1);
}
static int check_funcs(int file, int size, int daddress, int pec)
{
unsigned long funcs;
/* check adapter functionality */
if (ioctl(file, I2C_FUNCS, &funcs) < 0) {
fprintf(stderr, "Error: Could not get the adapter "
"functionality matrix: %s\n", strerror(errno));