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i2c_helper: Add support for the Linux I2C subsystem

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See https://www.kernel.org/doc/Documentation/i2c/ for details.

This creates common interface for I2C access functions, and adds
implementation for linux I2C functions.

BUG=b:148746232
BRANCH=none
TEST=build success

Signed-off-by: Shiyu Sun <sshiyu@chromium.org>
Change-Id: Ie0487824dfb71970bede17f617dbbb30ddf78c12
Reviewed-on: https://review.coreboot.org/c/flashrom/+/39686
Tested-by: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
This commit is contained in:
Shiyu Sun
2020-03-19 16:59:52 +11:00
committed by Edward O'Callaghan
parent fe6b98b91c
commit dc2c83bbc7
4 changed files with 239 additions and 0 deletions
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113
i2c_helper_linux.c Normal file
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/*
* This file is part of the flashrom project.
*
* Copyright (C) 2020 The Chromium OS Authors
*
* 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.
*/
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <sys/fcntl.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <stdlib.h>
#include <linux/i2c.h>
#include <linux/i2c-dev.h>
#include "flash.h"
#include "i2c_helper.h"
#define I2C_DEV_PREFIX "/dev/i2c-"
#define I2C_MAX_BUS 255
int i2c_close(int fd)
{
return fd == -1 ? 0 : close(fd);
}
int i2c_open(int bus, uint16_t addr, int force)
{
int ret = -1;
int fd = -1;
/* Maximum i2c bus number is 255(3 char), +1 for null terminated string. */
int path_len = strlen(I2C_DEV_PREFIX) + 4;
int request = force ? I2C_SLAVE_FORCE : I2C_SLAVE;
if (bus < 0 || bus > I2C_MAX_BUS) {
msg_perr("Invalid I2C bus %d.\n", bus);
return ret;
}
char *dev = calloc(1, path_len);
if (!dev) {
msg_perr("Unable to allocate space for device name of len %d: %s.\n",
path_len, strerror(errno));
goto linux_i2c_open_err;
}
ret = snprintf(dev, path_len, "%s%d", I2C_DEV_PREFIX, bus);
if (ret < 0) {
msg_perr("Unable to join bus number to device name: %s.\n", strerror(errno));
goto linux_i2c_open_err;
}
fd = open(dev, O_RDWR);
if (fd < 0) {
msg_perr("Unable to open I2C device %s: %s.\n", dev, strerror(errno));
ret = fd;
goto linux_i2c_open_err;
}
ret = ioctl(fd, request, addr);
if (ret < 0) {
msg_perr("Unable to set I2C slave address to 0x%02x: %s.\n", addr, strerror(errno));
i2c_close(fd);
goto linux_i2c_open_err;
}
linux_i2c_open_err:
if (dev)
free(dev);
return ret ? ret : fd;
}
int i2c_read(int fd, uint16_t addr, i2c_buffer_t *buf)
{
if (buf->len == 0)
return 0;
int ret = ioctl(fd, I2C_SLAVE, addr);
if (ret < 0) {
msg_perr("Unable to set I2C slave address to 0x%02x: %s.\n", addr, strerror(errno));
return ret;
}
return read(fd, buf->buf, buf->len);
}
int i2c_write(int fd, uint16_t addr, const i2c_buffer_t *buf)
{
if (buf->len == 0)
return 0;
int ret = ioctl(fd, I2C_SLAVE, addr);
if (ret < 0) {
msg_perr("Unable to set I2C slave address to 0x%02x: %s.\n", addr, strerror(errno));
return ret;
}
return write(fd, buf->buf, buf->len);
}