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/*
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;
/* Prevent 24rf08 corruption (in case of user error) */
if (kind < 0)
i2c_smbus_xfer(adapter, address, 0, 0, 0,
I2C_SMBUS_QUICK, NULL);
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);
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