kernel-ark/drivers/i2c/chips/max6875.c
Jean Delvare 4c9337da37 [PATCH] I2C: Centralize 24RF08 corruption prevention
The 24RF08 corruption would better be prevented at i2c-core level than
at chip driver level, for several reasons:
* The second quick write should happen as soon as possible after the
  first one, so as to limit the risk that another command is issued on
  the bus inbetween, causing the corruption.
* As a matter of fact, the protection code at driver level was reworked
  at least three times already, which proves how hard it is to get it
  right there, while it's straightforward at i2c-core level.
* It's easy to add a new driver that would need the protection, and
  forget to add it. This did happen already.
* As additional probing addresses can be passed to most i2c chip drivers
  as module parameters, virtually every i2c chip driver would need the
  protection if we want to be really safe.
* Why duplicate code when we can easily avoid it?

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2005-09-05 09:14:25 -07:00

262 lines
6.6 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 a bank of registers and two banks of EEPROM.
Address ranges are defined as follows:
* 0x0000 - 0x0046 = configuration registers
* 0x8000 - 0x8046 = configuration EEPROM
* 0x8100 - 0x82FF = user EEPROM
This driver makes the user EEPROM available for read.
The registers & config EEPROM should be accessed via i2c-dev.
The MAX6875 ignores the lowest address bit, so each chip responds to
two addresses - 0x50/0x51 and 0x52/0x53.
Note that the MAX6875 uses i2c_smbus_write_byte_data() to set the read
address, so this driver is destructive if loaded for the wrong EEPROM chip.
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/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <asm/semaphore.h>
/* Do not scan - the MAX6875 access method will write to some EEPROM chips */
static unsigned short normal_i2c[] = {I2C_CLIENT_END};
/* Insmod parameters */
I2C_CLIENT_INSMOD_1(max6875);
/* The MAX6875 can only read/write 16 bytes at a time */
#define SLICE_SIZE 16
#define SLICE_BITS 4
/* 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_BLK_READ 0x84
/* Each client has this additional data */
struct max6875_data {
struct i2c_client client;
struct semaphore update_lock;
u32 valid;
u8 data[USER_EEPROM_SIZE];
unsigned long last_updated[USER_EEPROM_SLICES];
};
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 void max6875_update_slice(struct i2c_client *client, int slice)
{
struct max6875_data *data = i2c_get_clientdata(client);
int i, j, addr;
u8 *buf;
if (slice >= USER_EEPROM_SLICES)
return;
down(&data->update_lock);
buf = &data->data[slice << SLICE_BITS];
if (!(data->valid & (1 << slice)) ||
time_after(jiffies, data->last_updated[slice])) {
dev_dbg(&client->dev, "Starting update of slice %u\n", slice);
data->valid &= ~(1 << slice);
addr = USER_EEPROM_BASE + (slice << SLICE_BITS);
/* select the eeprom address */
if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) {
dev_err(&client->dev, "address set failed\n");
goto exit_up;
}
if (i2c_check_functionality(client->adapter,
I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
if (i2c_smbus_read_i2c_block_data(client,
MAX6875_CMD_BLK_READ,
buf) != SLICE_SIZE) {
goto exit_up;
}
} else {
for (i = 0; i < SLICE_SIZE; i++) {
j = i2c_smbus_read_byte(client);
if (j < 0) {
goto exit_up;
}
buf[i] = j;
}
}
data->last_updated[slice] = jiffies;
data->valid |= (1 << slice);
}
exit_up:
up(&data->update_lock);
}
static ssize_t max6875_read(struct kobject *kobj, char *buf, loff_t off,
size_t count)
{
struct i2c_client *client = kobj_to_i2c_client(kobj);
struct max6875_data *data = i2c_get_clientdata(client);
int slice, max_slice;
if (off > USER_EEPROM_SIZE)
return 0;
if (off + count > USER_EEPROM_SIZE)
count = USER_EEPROM_SIZE - off;
/* refresh slices which contain requested bytes */
max_slice = (off + count - 1) >> SLICE_BITS;
for (slice = (off >> SLICE_BITS); slice <= max_slice; slice++)
max6875_update_slice(client, slice);
memcpy(buf, &data->data[off], count);
return count;
}
static struct bin_attribute user_eeprom_attr = {
.attr = {
.name = "eeprom",
.mode = S_IRUGO,
.owner = THIS_MODULE,
},
.size = USER_EEPROM_SIZE,
.read = max6875_read,
};
static int max6875_attach_adapter(struct i2c_adapter *adapter)
{
return i2c_probe(adapter, &addr_data, max6875_detect);
}
/* This function is called by i2c_probe */
static int max6875_detect(struct i2c_adapter *adapter, int address, int kind)
{
struct i2c_client *real_client;
struct i2c_client *fake_client;
struct max6875_data *data;
int err = 0;
if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA
| I2C_FUNC_SMBUS_READ_BYTE))
return 0;
/* Only check even addresses */
if (address & 1)
return 0;
if (!(data = kmalloc(sizeof(struct max6875_data), GFP_KERNEL)))
return -ENOMEM;
memset(data, 0, sizeof(struct max6875_data));
/* A fake client is created on the odd address */
if (!(fake_client = kmalloc(sizeof(struct i2c_client), GFP_KERNEL))) {
err = -ENOMEM;
goto exit_kfree1;
}
memset(fake_client, 0, sizeof(struct i2c_client));
/* Init real i2c_client */
real_client = &data->client;
i2c_set_clientdata(real_client, data);
real_client->addr = address;
real_client->adapter = adapter;
real_client->driver = &max6875_driver;
real_client->flags = 0;
strlcpy(real_client->name, "max6875", I2C_NAME_SIZE);
init_MUTEX(&data->update_lock);
/* Init fake client data */
/* set the client data to the i2c_client so that it will get freed */
i2c_set_clientdata(fake_client, fake_client);
fake_client->addr = address | 1;
fake_client->adapter = adapter;
fake_client->driver = &max6875_driver;
fake_client->flags = 0;
strlcpy(fake_client->name, "max6875 subclient", I2C_NAME_SIZE);
/* Prevent 24RF08 corruption (in case of user error) */
i2c_smbus_write_quick(real_client, 0);
if ((err = i2c_attach_client(real_client)) != 0)
goto exit_kfree2;
if ((err = i2c_attach_client(fake_client)) != 0)
goto exit_detach;
sysfs_create_bin_file(&real_client->dev.kobj, &user_eeprom_attr);
return 0;
exit_detach:
i2c_detach_client(real_client);
exit_kfree2:
kfree(fake_client);
exit_kfree1:
kfree(data);
return err;
}
static int max6875_detach_client(struct i2c_client *client)
{
int err;
err = i2c_detach_client(client);
if (err)
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);