android_kernel_xiaomi_sm8350/drivers/i2c/chips/max6875.c
Jean Delvare 9ab1ee2ab7 [PATCH] I2C: New max6875 driver may corrupt EEPROMs
After a careful code analysis on the new max6875 driver
(drivers/i2c/chips/max6875.c), I have come to the conclusion that this
driver may cause EEPROM corruptions if used on random systems.

The EEPROM part of the MAX6875 chip is accessed using rather uncommon
I2C sequences. What is seen by the MAX6875 as reads can be seen by a
standard EEPROM (24C02) as writes. If you check the detection method
used by the driver, you'll find that the first SMBus command it will
send on the bus is i2c_smbus_write_byte_data(client, 0x80, 0x40). For
the MAX6875 it makes an internal pointer point to a specific offset of
the EEPROM waiting for a subsequent read command, so it's not an actual
data write operation, but for a standard EEPROM, this instead means
writing value 0x40 to offset 0x80. Blame Philips and Intel for the
obscure protocol.

Since the MAX6875 and the standard, common 24C02 EEPROMs share two I2C
addresses (0x50 and 0x52), loading the max6875 driver on a system with
standard EEPROMs at either address will trigger a write on these
EEPROMs, which will lead to their corruption if they happen not to be
write protected. This kind of EEPROMs can be found on memory modules
(SPD), ethernet adapters (MAC address), laptops (proprietary data) and
displays (EDID/DDC). Most of these are hopefully write-protected, but
not all of them.

For this reason, I would recommend that the max6875 driver be
neutralized, in a way that nobody can corrupt his/her EEPROMs by just
loading the driver. This means either deleting the driver completely, or
not listing any default address for it. I'd like this to be done before
2.6.13-rc1 is released.

Additionally, the max6875 driver lacks the 24RF08 corruption preventer
present in the eeprom driver, which means that loading this driver in a
system with such a chip would corrupt it as well.

Here is a proposed quick patch addressing the issue, although I wouldn't
mind a complete removal if it makes everyone feel safer. I think Ben
has plans to replace this driver by a much simplified one anyway.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2005-07-11 14:10:36 -07:00

478 lines
14 KiB
C

/*
max6875.c - driver for MAX6874/MAX6875
Copyright (C) 2005 Ben Gardner <bgardner@wabtec.com>
Based on i2c/chips/eeprom.c
The MAX6875 has two EEPROM sections: config and user.
At reset, the config EEPROM is read into the registers.
This driver make 3 binary files available in sysfs:
reg_config - direct access to the registers
eeprom_config - acesses configuration eeprom space
eeprom_user - free for application use
In our application, we put device serial & model numbers in user eeprom.
Notes:
1) The datasheet says that register 0x44 / EEPROM 0x8044 should NOT
be overwritten, so the driver explicitly prevents that.
2) It's a good idea to keep the config (0x45) locked in config EEPROM.
You can temporarily enable config writes by changing register 0x45.
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; version 2 of the License.
*/
#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/i2c-sensor.h>
/* Addresses to scan */
/* No address scanned by default, as this could corrupt standard EEPROMS. */
static unsigned short normal_i2c[] = {I2C_CLIENT_END};
static unsigned int normal_isa[] = {I2C_CLIENT_ISA_END};
/* Insmod parameters */
SENSORS_INSMOD_1(max6875);
/* this param will prevent 'accidental' writes to the eeprom */
static int allow_write = 0;
module_param(allow_write, int, 0);
MODULE_PARM_DESC(allow_write,
"Enable write access:\n"
"*0: Read only\n"
" 1: Read/Write access");
/* The MAX6875 can only read/write 16 bytes at a time */
#define SLICE_SIZE 16
#define SLICE_BITS 4
/* CONFIG EEPROM is at addresses 0x8000 - 0x8045, registers are at 0 - 0x45 */
#define CONFIG_EEPROM_BASE 0x8000
#define CONFIG_EEPROM_SIZE 0x0046
#define CONFIG_EEPROM_SLICES 5
/* USER EEPROM is at addresses 0x8100 - 0x82FF */
#define USER_EEPROM_BASE 0x8100
#define USER_EEPROM_SIZE 0x0200
#define USER_EEPROM_SLICES 32
/* MAX6875 commands */
#define MAX6875_CMD_BLOCK_WRITE 0x83
#define MAX6875_CMD_BLOCK_READ 0x84
#define MAX6875_CMD_REBOOT 0x88
enum max6875_area_type {
max6875_register_config=0,
max6875_eeprom_config,
max6875_eeprom_user,
max6857_max
};
struct eeprom_block {
enum max6875_area_type type;
u8 slices;
u32 size;
u32 valid;
u32 base;
unsigned long *updated;
u8 *data;
};
/* Each client has this additional data */
struct max6875_data {
struct i2c_client client;
struct semaphore update_lock;
struct eeprom_block blocks[max6857_max];
/* the above structs point into the arrays below */
u8 data[USER_EEPROM_SIZE + (CONFIG_EEPROM_SIZE*2)];
unsigned long last_updated[USER_EEPROM_SLICES + (CONFIG_EEPROM_SLICES*2)];
};
static int max6875_attach_adapter(struct i2c_adapter *adapter);
static int max6875_detect(struct i2c_adapter *adapter, int address, int kind);
static int max6875_detach_client(struct i2c_client *client);
/* This is the driver that will be inserted */
static struct i2c_driver max6875_driver = {
.owner = THIS_MODULE,
.name = "max6875",
.flags = I2C_DF_NOTIFY,
.attach_adapter = max6875_attach_adapter,
.detach_client = max6875_detach_client,
};
static int max6875_update_slice(struct i2c_client *client,
struct eeprom_block *blk,
int slice)
{
struct max6875_data *data = i2c_get_clientdata(client);
int i, j, addr, count;
u8 rdbuf[SLICE_SIZE];
int retval = 0;
if (slice >= blk->slices)
return -1;
down(&data->update_lock);
if (!(blk->valid & (1 << slice)) ||
(jiffies - blk->updated[slice] > 300 * HZ) ||
(jiffies < blk->updated[slice])) {
dev_dbg(&client->dev, "Starting eeprom update, slice %u, base %u\n",
slice, blk->base);
addr = blk->base + (slice << SLICE_BITS);
count = blk->size - (slice << SLICE_BITS);
if (count > SLICE_SIZE) {
count = SLICE_SIZE;
}
/* Preset the read address */
if (addr < 0x100) {
/* select the register */
if (i2c_smbus_write_byte(client, addr & 0xFF)) {
dev_dbg(&client->dev, "max6875 register select has failed!\n");
retval = -1;
goto exit;
}
} else {
/* select the eeprom */
if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) {
dev_dbg(&client->dev, "max6875 address set has failed!\n");
retval = -1;
goto exit;
}
}
if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
if (i2c_smbus_read_i2c_block_data(client, MAX6875_CMD_BLOCK_READ,
rdbuf) != SLICE_SIZE)
{
retval = -1;
goto exit;
}
memcpy(&blk->data[slice << SLICE_BITS], rdbuf, count);
} else {
for (i = 0; i < count; i++) {
j = i2c_smbus_read_byte(client);
if (j < 0)
{
retval = -1;
goto exit;
}
blk->data[(slice << SLICE_BITS) + i] = (u8) j;
}
}
blk->updated[slice] = jiffies;
blk->valid |= (1 << slice);
}
exit:
up(&data->update_lock);
return retval;
}
static ssize_t max6875_read(struct kobject *kobj, char *buf, loff_t off, size_t count,
enum max6875_area_type area_type)
{
struct i2c_client *client = to_i2c_client(container_of(kobj, struct device, kobj));
struct max6875_data *data = i2c_get_clientdata(client);
struct eeprom_block *blk;
int slice;
blk = &data->blocks[area_type];
if (off > blk->size)
return 0;
if (off + count > blk->size)
count = blk->size - off;
/* Only refresh slices which contain requested bytes */
for (slice = (off >> SLICE_BITS); slice <= ((off + count - 1) >> SLICE_BITS); slice++)
max6875_update_slice(client, blk, slice);
memcpy(buf, &blk->data[off], count);
return count;
}
static ssize_t max6875_user_read(struct kobject *kobj, char *buf, loff_t off, size_t count)
{
return max6875_read(kobj, buf, off, count, max6875_eeprom_user);
}
static ssize_t max6875_config_read(struct kobject *kobj, char *buf, loff_t off, size_t count)
{
return max6875_read(kobj, buf, off, count, max6875_eeprom_config);
}
static ssize_t max6875_cfgreg_read(struct kobject *kobj, char *buf, loff_t off, size_t count)
{
return max6875_read(kobj, buf, off, count, max6875_register_config);
}
static ssize_t max6875_write(struct kobject *kobj, char *buf, loff_t off, size_t count,
enum max6875_area_type area_type)
{
struct i2c_client *client = to_i2c_client(container_of(kobj, struct device, kobj));
struct max6875_data *data = i2c_get_clientdata(client);
struct eeprom_block *blk;
int slice, addr, retval;
ssize_t sent = 0;
blk = &data->blocks[area_type];
if (off > blk->size)
return 0;
if ((off + count) > blk->size)
count = blk->size - off;
if (down_interruptible(&data->update_lock))
return -EAGAIN;
/* writing to a register is done with i2c_smbus_write_byte_data() */
if (blk->type == max6875_register_config) {
for (sent = 0; sent < count; sent++) {
addr = off + sent;
if (addr == 0x44)
continue;
retval = i2c_smbus_write_byte_data(client, addr, buf[sent]);
}
} else {
int cmd, val;
/* We are writing to EEPROM */
for (sent = 0; sent < count; sent++) {
addr = blk->base + off + sent;
cmd = addr >> 8;
val = (addr & 0xff) | (buf[sent] << 8); // reversed
if (addr == 0x8044)
continue;
retval = i2c_smbus_write_word_data(client, cmd, val);
if (retval) {
goto error_exit;
}
/* A write takes up to 11 ms */
msleep(11);
}
}
/* Invalidate the scratch buffer */
for (slice = (off >> SLICE_BITS); slice <= ((off + count - 1) >> SLICE_BITS); slice++)
blk->valid &= ~(1 << slice);
error_exit:
up(&data->update_lock);
return sent;
}
static ssize_t max6875_user_write(struct kobject *kobj, char *buf, loff_t off, size_t count)
{
return max6875_write(kobj, buf, off, count, max6875_eeprom_user);
}
static ssize_t max6875_config_write(struct kobject *kobj, char *buf, loff_t off, size_t count)
{
return max6875_write(kobj, buf, off, count, max6875_eeprom_config);
}
static ssize_t max6875_cfgreg_write(struct kobject *kobj, char *buf, loff_t off, size_t count)
{
return max6875_write(kobj, buf, off, count, max6875_register_config);
}
static struct bin_attribute user_eeprom_attr = {
.attr = {
.name = "eeprom_user",
.mode = S_IRUGO | S_IWUSR | S_IWGRP,
.owner = THIS_MODULE,
},
.size = USER_EEPROM_SIZE,
.read = max6875_user_read,
.write = max6875_user_write,
};
static struct bin_attribute config_eeprom_attr = {
.attr = {
.name = "eeprom_config",
.mode = S_IRUGO | S_IWUSR,
.owner = THIS_MODULE,
},
.size = CONFIG_EEPROM_SIZE,
.read = max6875_config_read,
.write = max6875_config_write,
};
static struct bin_attribute config_register_attr = {
.attr = {
.name = "reg_config",
.mode = S_IRUGO | S_IWUSR,
.owner = THIS_MODULE,
},
.size = CONFIG_EEPROM_SIZE,
.read = max6875_cfgreg_read,
.write = max6875_cfgreg_write,
};
static int max6875_attach_adapter(struct i2c_adapter *adapter)
{
return i2c_detect(adapter, &addr_data, max6875_detect);
}
/* This function is called by i2c_detect */
static int max6875_detect(struct i2c_adapter *adapter, int address, int kind)
{
struct i2c_client *new_client;
struct max6875_data *data;
int err = 0;
/* There are three ways we can read the EEPROM data:
(1) I2C block reads (faster, but unsupported by most adapters)
(2) Consecutive byte reads (100% overhead)
(3) Regular byte data reads (200% overhead)
The third method is not implemented by this driver because all
known adapters support at least the second. */
if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_BYTE_DATA |
I2C_FUNC_SMBUS_BYTE |
I2C_FUNC_SMBUS_WRITE_BYTE_DATA))
goto exit;
/* OK. For now, we presume we have a valid client. We now create the
client structure, even though we cannot fill it completely yet.
But it allows us to access eeprom_{read,write}_value. */
if (!(data = kmalloc(sizeof(struct max6875_data), GFP_KERNEL))) {
err = -ENOMEM;
goto exit;
}
memset(data, 0, sizeof(struct max6875_data));
new_client = &data->client;
i2c_set_clientdata(new_client, data);
new_client->addr = address;
new_client->adapter = adapter;
new_client->driver = &max6875_driver;
new_client->flags = 0;
/* Prevent 24RF08 corruption */
i2c_smbus_write_quick(new_client, 0);
/* Setup the user section */
data->blocks[max6875_eeprom_user].type = max6875_eeprom_user;
data->blocks[max6875_eeprom_user].slices = USER_EEPROM_SLICES;
data->blocks[max6875_eeprom_user].size = USER_EEPROM_SIZE;
data->blocks[max6875_eeprom_user].base = USER_EEPROM_BASE;
data->blocks[max6875_eeprom_user].data = data->data;
data->blocks[max6875_eeprom_user].updated = data->last_updated;
/* Setup the config section */
data->blocks[max6875_eeprom_config].type = max6875_eeprom_config;
data->blocks[max6875_eeprom_config].slices = CONFIG_EEPROM_SLICES;
data->blocks[max6875_eeprom_config].size = CONFIG_EEPROM_SIZE;
data->blocks[max6875_eeprom_config].base = CONFIG_EEPROM_BASE;
data->blocks[max6875_eeprom_config].data = &data->data[USER_EEPROM_SIZE];
data->blocks[max6875_eeprom_config].updated = &data->last_updated[USER_EEPROM_SLICES];
/* Setup the register section */
data->blocks[max6875_register_config].type = max6875_register_config;
data->blocks[max6875_register_config].slices = CONFIG_EEPROM_SLICES;
data->blocks[max6875_register_config].size = CONFIG_EEPROM_SIZE;
data->blocks[max6875_register_config].base = 0;
data->blocks[max6875_register_config].data = &data->data[USER_EEPROM_SIZE+CONFIG_EEPROM_SIZE];
data->blocks[max6875_register_config].updated = &data->last_updated[USER_EEPROM_SLICES+CONFIG_EEPROM_SLICES];
/* Init the data */
memset(data->data, 0xff, sizeof(data->data));
/* Fill in the remaining client fields */
strlcpy(new_client->name, "max6875", I2C_NAME_SIZE);
init_MUTEX(&data->update_lock);
/* Verify that the chip is really what we think it is */
if ((max6875_update_slice(new_client, &data->blocks[max6875_eeprom_config], 4) < 0) ||
(max6875_update_slice(new_client, &data->blocks[max6875_register_config], 4) < 0))
goto exit_kfree;
/* 0x41,0x42 must be zero and 0x40 must match in eeprom and registers */
if ((data->blocks[max6875_eeprom_config].data[0x41] != 0) ||
(data->blocks[max6875_eeprom_config].data[0x42] != 0) ||
(data->blocks[max6875_register_config].data[0x41] != 0) ||
(data->blocks[max6875_register_config].data[0x42] != 0) ||
(data->blocks[max6875_eeprom_config].data[0x40] !=
data->blocks[max6875_register_config].data[0x40]))
goto exit_kfree;
/* Tell the I2C layer a new client has arrived */
if ((err = i2c_attach_client(new_client)))
goto exit_kfree;
/* create the sysfs eeprom files with the correct permissions */
if (allow_write == 0) {
user_eeprom_attr.attr.mode &= ~S_IWUGO;
user_eeprom_attr.write = NULL;
config_eeprom_attr.attr.mode &= ~S_IWUGO;
config_eeprom_attr.write = NULL;
config_register_attr.attr.mode &= ~S_IWUGO;
config_register_attr.write = NULL;
}
sysfs_create_bin_file(&new_client->dev.kobj, &user_eeprom_attr);
sysfs_create_bin_file(&new_client->dev.kobj, &config_eeprom_attr);
sysfs_create_bin_file(&new_client->dev.kobj, &config_register_attr);
return 0;
exit_kfree:
kfree(data);
exit:
return err;
}
static int max6875_detach_client(struct i2c_client *client)
{
int err;
err = i2c_detach_client(client);
if (err) {
dev_err(&client->dev, "Client deregistration failed, client not detached.\n");
return err;
}
kfree(i2c_get_clientdata(client));
return 0;
}
static int __init max6875_init(void)
{
return i2c_add_driver(&max6875_driver);
}
static void __exit max6875_exit(void)
{
i2c_del_driver(&max6875_driver);
}
MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
MODULE_DESCRIPTION("MAX6875 driver");
MODULE_LICENSE("GPL");
module_init(max6875_init);
module_exit(max6875_exit);