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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * max6875.c - driver for MAX6874/MAX6875
4 *
5 * Copyright (C) 2005 Ben Gardner <[email protected]>
6 *
7 * Based on eeprom.c
8 *
9 * The MAX6875 has a bank of registers and two banks of EEPROM.
10 * Address ranges are defined as follows:
11 * * 0x0000 - 0x0046 = configuration registers
12 * * 0x8000 - 0x8046 = configuration EEPROM
13 * * 0x8100 - 0x82FF = user EEPROM
14 *
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 to
20 * two addresses - 0x50/0x51 and 0x52/0x53.
21 *
22 * Note that the MAX6875 uses i2c_smbus_write_byte_data() to set the read
23 * 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 16
34#define SLICE_BITS 4
35
36/* USER EEPROM is at addresses 0x8100 - 0x82FF */
37#define USER_EEPROM_BASE 0x8100
38#define USER_EEPROM_SIZE 0x0200
39#define USER_EEPROM_SLICES 32
40
41/* MAX6875 commands */
42#define MAX6875_CMD_BLK_READ 0x84
43
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 const 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_DATA
140 | 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_obj(struct max6875_data);
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 { .name = "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 <[email protected]>");
203MODULE_DESCRIPTION("MAX6875 driver");
204MODULE_LICENSE("GPL");