1/*
2 * I2C slave mode EEPROM simulator
3 *
4 * Copyright (C) 2014 by Wolfram Sang, Sang Engineering <wsa@sang-engineering.com>
5 * Copyright (C) 2014 by Renesas Electronics Corporation
6 *
7 * This program is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU General Public License as published by the
9 * Free Software Foundation; version 2 of the License.
10 *
11 * Because most IP blocks can only detect one I2C slave address anyhow, this
12 * driver does not support simulating EEPROM types which take more than one
13 * address. It is prepared to simulate bigger EEPROMs with an internal 16 bit
14 * pointer, yet implementation is deferred until the need actually arises.
15 */
16
17#include <linux/i2c.h>
18#include <linux/init.h>
19#include <linux/module.h>
20#include <linux/of.h>
21#include <linux/slab.h>
22#include <linux/spinlock.h>
23#include <linux/sysfs.h>
24
25struct eeprom_data {
26 struct bin_attribute bin;
27 bool first_write;
28 spinlock_t buffer_lock;
29 u8 buffer_idx;
30 u8 buffer[];
31};
32
33static int i2c_slave_eeprom_slave_cb(struct i2c_client *client,
34 enum i2c_slave_event event, u8 *val)
35{
36 struct eeprom_data *eeprom = i2c_get_clientdata(client);
37
38 switch (event) {
39 case I2C_SLAVE_WRITE_RECEIVED:
40 if (eeprom->first_write) {
41 eeprom->buffer_idx = *val;
42 eeprom->first_write = false;
43 } else {
44 spin_lock(&eeprom->buffer_lock);
45 eeprom->buffer[eeprom->buffer_idx++] = *val;
46 spin_unlock(&eeprom->buffer_lock);
47 }
48 break;
49
50 case I2C_SLAVE_READ_PROCESSED:
51 /* The previous byte made it to the bus, get next one */
52 eeprom->buffer_idx++;
53 /* fallthrough */
54 case I2C_SLAVE_READ_REQUESTED:
55 spin_lock(&eeprom->buffer_lock);
56 *val = eeprom->buffer[eeprom->buffer_idx];
57 spin_unlock(&eeprom->buffer_lock);
58 /*
59 * Do not increment buffer_idx here, because we don't know if
60 * this byte will be actually used. Read Linux I2C slave docs
61 * for details.
62 */
63 break;
64
65 case I2C_SLAVE_STOP:
66 case I2C_SLAVE_WRITE_REQUESTED:
67 eeprom->first_write = true;
68 break;
69
70 default:
71 break;
72 }
73
74 return 0;
75}
76
77static ssize_t i2c_slave_eeprom_bin_read(struct file *filp, struct kobject *kobj,
78 struct bin_attribute *attr, char *buf, loff_t off, size_t count)
79{
80 struct eeprom_data *eeprom;
81 unsigned long flags;
82
83 eeprom = dev_get_drvdata(container_of(kobj, struct device, kobj));
84
85 spin_lock_irqsave(&eeprom->buffer_lock, flags);
86 memcpy(buf, &eeprom->buffer[off], count);
87 spin_unlock_irqrestore(&eeprom->buffer_lock, flags);
88
89 return count;
90}
91
92static ssize_t i2c_slave_eeprom_bin_write(struct file *filp, struct kobject *kobj,
93 struct bin_attribute *attr, char *buf, loff_t off, size_t count)
94{
95 struct eeprom_data *eeprom;
96 unsigned long flags;
97
98 eeprom = dev_get_drvdata(container_of(kobj, struct device, kobj));
99
100 spin_lock_irqsave(&eeprom->buffer_lock, flags);
101 memcpy(&eeprom->buffer[off], buf, count);
102 spin_unlock_irqrestore(&eeprom->buffer_lock, flags);
103
104 return count;
105}
106
107static int i2c_slave_eeprom_probe(struct i2c_client *client, const struct i2c_device_id *id)
108{
109 struct eeprom_data *eeprom;
110 int ret;
111 unsigned size = id->driver_data;
112
113 eeprom = devm_kzalloc(&client->dev, sizeof(struct eeprom_data) + size, GFP_KERNEL);
114 if (!eeprom)
115 return -ENOMEM;
116
117 eeprom->first_write = true;
118 spin_lock_init(&eeprom->buffer_lock);
119 i2c_set_clientdata(client, eeprom);
120
121 sysfs_bin_attr_init(&eeprom->bin);
122 eeprom->bin.attr.name = "slave-eeprom";
123 eeprom->bin.attr.mode = S_IRUSR | S_IWUSR;
124 eeprom->bin.read = i2c_slave_eeprom_bin_read;
125 eeprom->bin.write = i2c_slave_eeprom_bin_write;
126 eeprom->bin.size = size;
127
128 ret = sysfs_create_bin_file(&client->dev.kobj, &eeprom->bin);
129 if (ret)
130 return ret;
131
132 ret = i2c_slave_register(client, i2c_slave_eeprom_slave_cb);
133 if (ret) {
134 sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
135 return ret;
136 }
137
138 return 0;
139};
140
141static int i2c_slave_eeprom_remove(struct i2c_client *client)
142{
143 struct eeprom_data *eeprom = i2c_get_clientdata(client);
144
145 i2c_slave_unregister(client);
146 sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
147
148 return 0;
149}
150
151static const struct i2c_device_id i2c_slave_eeprom_id[] = {
152 { "slave-24c02", 2048 / 8 },
153 { }
154};
155MODULE_DEVICE_TABLE(i2c, i2c_slave_eeprom_id);
156
157static struct i2c_driver i2c_slave_eeprom_driver = {
158 .driver = {
159 .name = "i2c-slave-eeprom",
160 },
161 .probe = i2c_slave_eeprom_probe,
162 .remove = i2c_slave_eeprom_remove,
163 .id_table = i2c_slave_eeprom_id,
164};
165module_i2c_driver(i2c_slave_eeprom_driver);
166
167MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
168MODULE_DESCRIPTION("I2C slave mode EEPROM simulator");
169MODULE_LICENSE("GPL v2");
170