205 lines · c
1// SPDX-License-Identifier: GPL-2.0-only2/*3 * max6875.c - driver for MAX6874/MAX68754 *5 * Copyright (C) 2005 Ben Gardner <bgardner@wabtec.com>6 *7 * Based on eeprom.c8 *9 * The MAX6875 has a bank of registers and two banks of EEPROM.10 * Address ranges are defined as follows:11 * * 0x0000 - 0x0046 = configuration registers12 * * 0x8000 - 0x8046 = configuration EEPROM13 * * 0x8100 - 0x82FF = user EEPROM14 *15 * This driver makes the user EEPROM available for read.16 *17 * The registers & config EEPROM should be accessed via i2c-dev.18 *19 * The MAX6875 ignores the lowest address bit, so each chip responds to20 * two addresses - 0x50/0x51 and 0x52/0x53.21 *22 * Note that the MAX6875 uses i2c_smbus_write_byte_data() to set the read23 * address, so this driver is destructive if loaded for the wrong EEPROM chip.24 */25 26#include <linux/kernel.h>27#include <linux/module.h>28#include <linux/slab.h>29#include <linux/i2c.h>30#include <linux/mutex.h>31 32/* The MAX6875 can only read/write 16 bytes at a time */33#define SLICE_SIZE 1634#define SLICE_BITS 435 36/* USER EEPROM is at addresses 0x8100 - 0x82FF */37#define USER_EEPROM_BASE 0x810038#define USER_EEPROM_SIZE 0x020039#define USER_EEPROM_SLICES 3240 41/* MAX6875 commands */42#define MAX6875_CMD_BLK_READ 0x8443 44/* Each client has this additional data */45struct max6875_data {46 struct i2c_client *fake_client;47 struct mutex update_lock;48 49 u32 valid;50 u8 data[USER_EEPROM_SIZE];51 unsigned long last_updated[USER_EEPROM_SLICES];52};53 54static void max6875_update_slice(struct i2c_client *client, int slice)55{56 struct max6875_data *data = i2c_get_clientdata(client);57 int i, j, addr;58 u8 *buf;59 60 if (slice >= USER_EEPROM_SLICES)61 return;62 63 mutex_lock(&data->update_lock);64 65 buf = &data->data[slice << SLICE_BITS];66 67 if (!(data->valid & (1 << slice)) ||68 time_after(jiffies, data->last_updated[slice])) {69 70 dev_dbg(&client->dev, "Starting update of slice %u\n", slice);71 72 data->valid &= ~(1 << slice);73 74 addr = USER_EEPROM_BASE + (slice << SLICE_BITS);75 76 /* select the eeprom address */77 if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) {78 dev_err(&client->dev, "address set failed\n");79 goto exit_up;80 }81 82 if (i2c_check_functionality(client->adapter,83 I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {84 if (i2c_smbus_read_i2c_block_data(client,85 MAX6875_CMD_BLK_READ,86 SLICE_SIZE,87 buf) != SLICE_SIZE) {88 goto exit_up;89 }90 } else {91 for (i = 0; i < SLICE_SIZE; i++) {92 j = i2c_smbus_read_byte(client);93 if (j < 0) {94 goto exit_up;95 }96 buf[i] = j;97 }98 }99 data->last_updated[slice] = jiffies;100 data->valid |= (1 << slice);101 }102exit_up:103 mutex_unlock(&data->update_lock);104}105 106static ssize_t max6875_read(struct file *filp, struct kobject *kobj,107 struct bin_attribute *bin_attr,108 char *buf, loff_t off, size_t count)109{110 struct i2c_client *client = kobj_to_i2c_client(kobj);111 struct max6875_data *data = i2c_get_clientdata(client);112 int slice, max_slice;113 114 /* refresh slices which contain requested bytes */115 max_slice = (off + count - 1) >> SLICE_BITS;116 for (slice = (off >> SLICE_BITS); slice <= max_slice; slice++)117 max6875_update_slice(client, slice);118 119 memcpy(buf, &data->data[off], count);120 121 return count;122}123 124static const struct bin_attribute user_eeprom_attr = {125 .attr = {126 .name = "eeprom",127 .mode = S_IRUGO,128 },129 .size = USER_EEPROM_SIZE,130 .read = max6875_read,131};132 133static int max6875_probe(struct i2c_client *client)134{135 struct i2c_adapter *adapter = client->adapter;136 struct max6875_data *data;137 int err;138 139 if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE_DATA140 | I2C_FUNC_SMBUS_READ_BYTE))141 return -ENODEV;142 143 /* Only bind to even addresses */144 if (client->addr & 1)145 return -ENODEV;146 147 data = kzalloc(sizeof(struct max6875_data), GFP_KERNEL);148 if (!data)149 return -ENOMEM;150 151 /* A fake client is created on the odd address */152 data->fake_client = i2c_new_dummy_device(client->adapter, client->addr + 1);153 if (IS_ERR(data->fake_client)) {154 err = PTR_ERR(data->fake_client);155 goto exit_kfree;156 }157 158 /* Init real i2c_client */159 i2c_set_clientdata(client, data);160 mutex_init(&data->update_lock);161 162 err = sysfs_create_bin_file(&client->dev.kobj, &user_eeprom_attr);163 if (err)164 goto exit_remove_fake;165 166 return 0;167 168exit_remove_fake:169 i2c_unregister_device(data->fake_client);170exit_kfree:171 kfree(data);172 return err;173}174 175static void max6875_remove(struct i2c_client *client)176{177 struct max6875_data *data = i2c_get_clientdata(client);178 179 i2c_unregister_device(data->fake_client);180 181 sysfs_remove_bin_file(&client->dev.kobj, &user_eeprom_attr);182 kfree(data);183}184 185static const struct i2c_device_id max6875_id[] = {186 { "max6875" },187 { }188};189MODULE_DEVICE_TABLE(i2c, max6875_id);190 191static struct i2c_driver max6875_driver = {192 .driver = {193 .name = "max6875",194 },195 .probe = max6875_probe,196 .remove = max6875_remove,197 .id_table = max6875_id,198};199 200module_i2c_driver(max6875_driver);201 202MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");203MODULE_DESCRIPTION("MAX6875 driver");204MODULE_LICENSE("GPL");205