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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");
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * I2C slave mode EEPROM simulator
4 *
5 * Copyright (C) 2014 by Wolfram Sang, Sang Engineering <wsa@sang-engineering.com>
6 * Copyright (C) 2014 by Renesas Electronics Corporation
7 *
8 * Because most slave IP cores can only detect one I2C slave address anyhow,
9 * this driver does not support simulating EEPROM types which take more than
10 * one address.
11 */
12
13/*
14 * FIXME: What to do if only 8 bits of a 16 bit address are sent?
15 * The ST-M24C64 sends only 0xff then. Needs verification with other
16 * EEPROMs, though. We currently use the 8 bit as a valid address.
17 */
18
19#include <linux/bitfield.h>
20#include <linux/firmware.h>
21#include <linux/i2c.h>
22#include <linux/init.h>
23#include <linux/module.h>
24#include <linux/of.h>
25#include <linux/slab.h>
26#include <linux/spinlock.h>
27#include <linux/sysfs.h>
28
29struct eeprom_data {
30 struct bin_attribute bin;
31 spinlock_t buffer_lock;
32 u16 buffer_idx;
33 u16 address_mask;
34 u8 num_address_bytes;
35 u8 idx_write_cnt;
36 bool read_only;
37 u8 buffer[];
38};
39
40#define I2C_SLAVE_BYTELEN GENMASK(15, 0)
41#define I2C_SLAVE_FLAG_ADDR16 BIT(16)
42#define I2C_SLAVE_FLAG_RO BIT(17)
43#define I2C_SLAVE_DEVICE_MAGIC(_len, _flags) ((_flags) | ((_len) - 1))
44
45static int i2c_slave_eeprom_slave_cb(struct i2c_client *client,
46 enum i2c_slave_event event, u8 *val)
47{
48 struct eeprom_data *eeprom = i2c_get_clientdata(client);
49
50 switch (event) {
51 case I2C_SLAVE_WRITE_RECEIVED:
52 if (eeprom->idx_write_cnt < eeprom->num_address_bytes) {
53 if (eeprom->idx_write_cnt == 0)
54 eeprom->buffer_idx = 0;
55 eeprom->buffer_idx = *val | (eeprom->buffer_idx << 8);
56 eeprom->idx_write_cnt++;
57 } else {
58 if (!eeprom->read_only) {
59 spin_lock(&eeprom->buffer_lock);
60 eeprom->buffer[eeprom->buffer_idx++ & eeprom->address_mask] = *val;
61 spin_unlock(&eeprom->buffer_lock);
62 }
63 }
64 break;
65
66 case I2C_SLAVE_READ_PROCESSED:
67 /* The previous byte made it to the bus, get next one */
68 eeprom->buffer_idx++;
69 fallthrough;
70 case I2C_SLAVE_READ_REQUESTED:
71 spin_lock(&eeprom->buffer_lock);
72 *val = eeprom->buffer[eeprom->buffer_idx & eeprom->address_mask];
73 spin_unlock(&eeprom->buffer_lock);
74 /*
75 * Do not increment buffer_idx here, because we don't know if
76 * this byte will be actually used. Read Linux I2C slave docs
77 * for details.
78 */
79 break;
80
81 case I2C_SLAVE_STOP:
82 case I2C_SLAVE_WRITE_REQUESTED:
83 eeprom->idx_write_cnt = 0;
84 break;
85
86 default:
87 break;
88 }
89
90 return 0;
91}
92
93static ssize_t i2c_slave_eeprom_bin_read(struct file *filp, struct kobject *kobj,
94 struct bin_attribute *attr, char *buf, loff_t off, size_t count)
95{
96 struct eeprom_data *eeprom;
97 unsigned long flags;
98
99 eeprom = dev_get_drvdata(kobj_to_dev(kobj));
100
101 spin_lock_irqsave(&eeprom->buffer_lock, flags);
102 memcpy(buf, &eeprom->buffer[off], count);
103 spin_unlock_irqrestore(&eeprom->buffer_lock, flags);
104
105 return count;
106}
107
108static ssize_t i2c_slave_eeprom_bin_write(struct file *filp, struct kobject *kobj,
109 struct bin_attribute *attr, char *buf, loff_t off, size_t count)
110{
111 struct eeprom_data *eeprom;
112 unsigned long flags;
113
114 eeprom = dev_get_drvdata(kobj_to_dev(kobj));
115
116 spin_lock_irqsave(&eeprom->buffer_lock, flags);
117 memcpy(&eeprom->buffer[off], buf, count);
118 spin_unlock_irqrestore(&eeprom->buffer_lock, flags);
119
120 return count;
121}
122
123static int i2c_slave_init_eeprom_data(struct eeprom_data *eeprom, struct i2c_client *client,
124 unsigned int size)
125{
126 const struct firmware *fw;
127 const char *eeprom_data;
128 int ret = device_property_read_string(&client->dev, "firmware-name", &eeprom_data);
129
130 if (!ret) {
131 ret = request_firmware_into_buf(&fw, eeprom_data, &client->dev,
132 eeprom->buffer, size);
133 if (ret)
134 return ret;
135 release_firmware(fw);
136 } else {
137 /* An empty eeprom typically has all bits set to 1 */
138 memset(eeprom->buffer, 0xff, size);
139 }
140 return 0;
141}
142
143static int i2c_slave_eeprom_probe(struct i2c_client *client)
144{
145 const struct i2c_device_id *id = i2c_client_get_device_id(client);
146 struct eeprom_data *eeprom;
147 int ret;
148 unsigned int size = FIELD_GET(I2C_SLAVE_BYTELEN, id->driver_data) + 1;
149 unsigned int flag_addr16 = FIELD_GET(I2C_SLAVE_FLAG_ADDR16, id->driver_data);
150
151 eeprom = devm_kzalloc(&client->dev, sizeof(struct eeprom_data) + size, GFP_KERNEL);
152 if (!eeprom)
153 return -ENOMEM;
154
155 eeprom->num_address_bytes = flag_addr16 ? 2 : 1;
156 eeprom->address_mask = size - 1;
157 eeprom->read_only = FIELD_GET(I2C_SLAVE_FLAG_RO, id->driver_data);
158 spin_lock_init(&eeprom->buffer_lock);
159 i2c_set_clientdata(client, eeprom);
160
161 ret = i2c_slave_init_eeprom_data(eeprom, client, size);
162 if (ret)
163 return ret;
164
165 sysfs_bin_attr_init(&eeprom->bin);
166 eeprom->bin.attr.name = "slave-eeprom";
167 eeprom->bin.attr.mode = S_IRUSR | S_IWUSR;
168 eeprom->bin.read = i2c_slave_eeprom_bin_read;
169 eeprom->bin.write = i2c_slave_eeprom_bin_write;
170 eeprom->bin.size = size;
171
172 ret = sysfs_create_bin_file(&client->dev.kobj, &eeprom->bin);
173 if (ret)
174 return ret;
175
176 ret = i2c_slave_register(client, i2c_slave_eeprom_slave_cb);
177 if (ret) {
178 sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
179 return ret;
180 }
181
182 return 0;
183};
184
185static void i2c_slave_eeprom_remove(struct i2c_client *client)
186{
187 struct eeprom_data *eeprom = i2c_get_clientdata(client);
188
189 i2c_slave_unregister(client);
190 sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
191}
192
193static const struct i2c_device_id i2c_slave_eeprom_id[] = {
194 { "slave-24c02", I2C_SLAVE_DEVICE_MAGIC(2048 / 8, 0) },
195 { "slave-24c02ro", I2C_SLAVE_DEVICE_MAGIC(2048 / 8, I2C_SLAVE_FLAG_RO) },
196 { "slave-24c32", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16) },
197 { "slave-24c32ro", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },
198 { "slave-24c64", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16) },
199 { "slave-24c64ro", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },
200 { "slave-24c512", I2C_SLAVE_DEVICE_MAGIC(524288 / 8, I2C_SLAVE_FLAG_ADDR16) },
201 { "slave-24c512ro", I2C_SLAVE_DEVICE_MAGIC(524288 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },
202 { }
203};
204MODULE_DEVICE_TABLE(i2c, i2c_slave_eeprom_id);
205
206static struct i2c_driver i2c_slave_eeprom_driver = {
207 .driver = {
208 .name = "i2c-slave-eeprom",
209 },
210 .probe_new = i2c_slave_eeprom_probe,
211 .remove = i2c_slave_eeprom_remove,
212 .id_table = i2c_slave_eeprom_id,
213};
214module_i2c_driver(i2c_slave_eeprom_driver);
215
216MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
217MODULE_DESCRIPTION("I2C slave mode EEPROM simulator");
218MODULE_LICENSE("GPL v2");