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// SPDX-License-Identifier: GPL-2.0-only
/*
* max6875.c - driver for MAX6874/MAX6875
*
* Copyright (C) 2005 Ben Gardner <bgardner@wabtec.com>
*
* Based on 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.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/mutex.h>
/* 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 *fake_client;
struct mutex update_lock;
u32 valid;
u8 data[USER_EEPROM_SIZE];
unsigned long last_updated[USER_EEPROM_SLICES];
};
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;
mutex_lock(&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,
SLICE_SIZE,
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:
mutex_unlock(&data->update_lock);
}
static ssize_t max6875_read(struct file *filp, struct kobject *kobj,
struct bin_attribute *bin_attr,
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;
/* 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 const struct bin_attribute user_eeprom_attr = {
.attr = {
.name = "eeprom",
.mode = S_IRUGO,
},
.size = USER_EEPROM_SIZE,
.read = max6875_read,
};
static int max6875_probe(struct i2c_client *client)
{
struct i2c_adapter *adapter = client->adapter;
struct max6875_data *data;
int err;
if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA
| I2C_FUNC_SMBUS_READ_BYTE))
return -ENODEV;
/* Only bind to even addresses */
if (client->addr & 1)
return -ENODEV;
data = kzalloc(sizeof(struct max6875_data), GFP_KERNEL);
if (!data)
return -ENOMEM;
/* A fake client is created on the odd address */
data->fake_client = i2c_new_dummy_device(client->adapter, client->addr + 1);
if (IS_ERR(data->fake_client)) {
err = PTR_ERR(data->fake_client);
goto exit_kfree;
}
/* Init real i2c_client */
i2c_set_clientdata(client, data);
mutex_init(&data->update_lock);
err = sysfs_create_bin_file(&client->dev.kobj, &user_eeprom_attr);
if (err)
goto exit_remove_fake;
return 0;
exit_remove_fake:
i2c_unregister_device(data->fake_client);
exit_kfree:
kfree(data);
return err;
}
static void max6875_remove(struct i2c_client *client)
{
struct max6875_data *data = i2c_get_clientdata(client);
i2c_unregister_device(data->fake_client);
sysfs_remove_bin_file(&client->dev.kobj, &user_eeprom_attr);
kfree(data);
}
static const struct i2c_device_id max6875_id[] = {
{ "max6875", 0 },
{ }
};
MODULE_DEVICE_TABLE(i2c, max6875_id);
static struct i2c_driver max6875_driver = {
.driver = {
.name = "max6875",
},
.probe_new = max6875_probe,
.remove = max6875_remove,
.id_table = max6875_id,
};
module_i2c_driver(max6875_driver);
MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
MODULE_DESCRIPTION("MAX6875 driver");
MODULE_LICENSE("GPL");
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