root/i2c-tools/trunk/tools/i2cget.c

/*
    i2cget.c - A user-space program to read an I2C register.
    Copyright (C) 2005-2008  Jean Delvare <khali@linux-fr.org>

    Based on i2cset.c:
    Copyright (C) 2001-2003  Frodo Looijaard <frodol@dds.nl>, and
                             Mark D. Studebaker <mdsxyz123@yahoo.com>
    Copyright (C) 2004-2005  Jean Delvare <khali@linux-fr.org>

    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 <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));
                return -1;
        }

        switch (size) {
        case I2C_SMBUS_BYTE:
                if (!(funcs & I2C_FUNC_SMBUS_READ_BYTE)) {
                        fprintf(stderr, MISSING_FUNC_FMT, "SMBus receive byte");
                        return -1;
                }
                if (daddress >= 0
                 && !(funcs & I2C_FUNC_SMBUS_WRITE_BYTE)) {
                        fprintf(stderr, MISSING_FUNC_FMT, "SMBus send byte");
                        return -1;
                }
                break;

        case I2C_SMBUS_BYTE_DATA:
                if (!(funcs & I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
                        fprintf(stderr, MISSING_FUNC_FMT, "SMBus read byte");
                        return -1;
                }
                break;

        case I2C_SMBUS_WORD_DATA:
                if (!(funcs & I2C_FUNC_SMBUS_READ_WORD_DATA)) {
                        fprintf(stderr, MISSING_FUNC_FMT, "SMBus read word");
                        return -1;
                }
                break;
        }

        if (pec
         && !(funcs & (I2C_FUNC_SMBUS_PEC | I2C_FUNC_I2C))) {
                fprintf(stderr, "Warning: Adapter does "
                        "not seem to support PEC\n");
        }

        return 0;
}

static int confirm(const char *filename, int address, int size, int daddress,
                   int pec)
{
        int dont = 0;

        fprintf(stderr, "WARNING! This program can confuse your I2C "
                "bus, cause data loss and worse!\n");

        /* Don't let the user break his/her EEPROMs */
        if (address >= 0x50 && address <= 0x57 && pec) {
                fprintf(stderr, "STOP! EEPROMs are I2C devices, not "
                        "SMBus devices. Using PEC\non I2C devices may "
                        "result in unexpected results, such as\n"
                        "trashing the contents of EEPROMs. We can't "
                        "let you do that, sorry.\n");
                return 0;
        }

        if (size == I2C_SMBUS_BYTE && daddress >= 0 && pec) {
                fprintf(stderr, "WARNING! All I2C chips and some SMBus chips "
                        "will interpret a write\nbyte command with PEC as a"
                        "write byte data command, effectively writing a\n"
                        "value into a register!\n");
                dont++;
        }

        fprintf(stderr, "I will read from device file %s, chip "
                "address 0x%02x, ", filename, address);
        if (daddress < 0)
                fprintf(stderr, "current data\naddress");
        else
                fprintf(stderr, "data address\n0x%02x", daddress);
        fprintf(stderr, ", using %s.\n",
                size == I2C_SMBUS_BYTE ? (daddress < 0 ?
                "read byte" : "write byte/read byte") :
                size == I2C_SMBUS_BYTE_DATA ? "read byte data" :
                "read word data");
        if (pec)
                fprintf(stderr, "PEC checking enabled.\n");

        fprintf(stderr, "Continue? [%s] ", dont ? "y/N" : "Y/n");
        fflush(stderr);
        if (!user_ack(!dont)) {
                fprintf(stderr, "Aborting on user request.\n");
                return 0;
        }

        return 1;
}

int main(int argc, char *argv[])
{
        char *end;
        int res, i2cbus, address, size, file;
        int daddress;
        char filename[20];
        int pec = 0;
        int flags = 0;
        int force = 0, yes = 0, version = 0;

        /* handle (optional) flags first */
        while (1+flags < argc && argv[1+flags][0] == '-') {
                switch (argv[1+flags][1]) {
                case 'V': version = 1; break;
                case 'f': force = 1; break;
                case 'y': yes = 1; break;
                default:
                        fprintf(stderr, "Error: Unsupported option "
                                "\"%s\"!\n", argv[1+flags]);
                        help();
                        exit(1);
                }
                flags++;
        }

        if (version) {
                fprintf(stderr, "i2cget version %s\n", VERSION);
                exit(0);
        }

        if (argc < flags + 3)
                help();

        i2cbus = lookup_i2c_bus(argv[flags+1]);
        if (i2cbus < 0)
                help();

        address = parse_i2c_address(argv[flags+2]);
        if (address < 0)
                help();

        if (argc > flags + 3) {
                size = I2C_SMBUS_BYTE_DATA;
                daddress = strtol(argv[flags+3], &end, 0);
                if (*end || daddress < 0 || daddress > 0xff) {
                        fprintf(stderr, "Error: Data address invalid!\n");
                        help();
                }
        } else {
                size = I2C_SMBUS_BYTE;
                daddress = -1;
        }

        if (argc > flags + 4) {
                switch (argv[flags+4][0]) {
                case 'b': size = I2C_SMBUS_BYTE_DATA; break;
                case 'w': size = I2C_SMBUS_WORD_DATA; break;
                case 'c': size = I2C_SMBUS_BYTE; break;
                default:
                        fprintf(stderr, "Error: Invalid mode!\n");
                        help();
                }
                pec = argv[flags+4][1] == 'p';
        }

        file = open_i2c_dev(i2cbus, filename, 0);
        if (file < 0
         || check_funcs(file, size, daddress, pec)
         || set_slave_addr(file, address, force))
                exit(1);

        if (!yes && !confirm(filename, address, size, daddress, pec))
                exit(0);

        if (pec && ioctl(file, I2C_PEC, 1) < 0) {
                fprintf(stderr, "Error: Could not set PEC: %s\n",
                        strerror(errno));
                close(file);
                exit(1);
        }

        switch (size) {
        case I2C_SMBUS_BYTE:
                if (daddress >= 0) {
                        res = i2c_smbus_write_byte(file, daddress);
                        if (res < 0)
                                fprintf(stderr, "Warning - write failed\n");
                }
                res = i2c_smbus_read_byte(file);
                break;
        case I2C_SMBUS_WORD_DATA:
                res = i2c_smbus_read_word_data(file, daddress);
                break;
        default: /* I2C_SMBUS_BYTE_DATA */
                res = i2c_smbus_read_byte_data(file, daddress);
        }
        close(file);

        if (res < 0) {
                fprintf(stderr, "Error: Read failed\n");
                exit(2);
        }

        printf("0x%0*x\n", size == I2C_SMBUS_WORD_DATA ? 4 : 2, res);

        exit(0);
}