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
29 struct 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
i2c_slave_eeprom_slave_cb(struct i2c_client * client,enum i2c_slave_event event,u8 * val)45 static 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
i2c_slave_eeprom_bin_read(struct file * filp,struct kobject * kobj,struct bin_attribute * attr,char * buf,loff_t off,size_t count)93 static 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
i2c_slave_eeprom_bin_write(struct file * filp,struct kobject * kobj,struct bin_attribute * attr,char * buf,loff_t off,size_t count)108 static 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
i2c_slave_init_eeprom_data(struct eeprom_data * eeprom,struct i2c_client * client,unsigned int size)123 static 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
i2c_slave_eeprom_probe(struct i2c_client * client,const struct i2c_device_id * id)143 static int i2c_slave_eeprom_probe(struct i2c_client *client, const struct i2c_device_id *id)
144 {
145 struct eeprom_data *eeprom;
146 int ret;
147 unsigned int size = FIELD_GET(I2C_SLAVE_BYTELEN, id->driver_data) + 1;
148 unsigned int flag_addr16 = FIELD_GET(I2C_SLAVE_FLAG_ADDR16, id->driver_data);
149
150 eeprom = devm_kzalloc(&client->dev, sizeof(struct eeprom_data) + size, GFP_KERNEL);
151 if (!eeprom)
152 return -ENOMEM;
153
154 eeprom->num_address_bytes = flag_addr16 ? 2 : 1;
155 eeprom->address_mask = size - 1;
156 eeprom->read_only = FIELD_GET(I2C_SLAVE_FLAG_RO, id->driver_data);
157 spin_lock_init(&eeprom->buffer_lock);
158 i2c_set_clientdata(client, eeprom);
159
160 ret = i2c_slave_init_eeprom_data(eeprom, client, size);
161 if (ret)
162 return ret;
163
164 sysfs_bin_attr_init(&eeprom->bin);
165 eeprom->bin.attr.name = "slave-eeprom";
166 eeprom->bin.attr.mode = S_IRUSR | S_IWUSR;
167 eeprom->bin.read = i2c_slave_eeprom_bin_read;
168 eeprom->bin.write = i2c_slave_eeprom_bin_write;
169 eeprom->bin.size = size;
170
171 ret = sysfs_create_bin_file(&client->dev.kobj, &eeprom->bin);
172 if (ret)
173 return ret;
174
175 ret = i2c_slave_register(client, i2c_slave_eeprom_slave_cb);
176 if (ret) {
177 sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
178 return ret;
179 }
180
181 return 0;
182 };
183
i2c_slave_eeprom_remove(struct i2c_client * client)184 static int i2c_slave_eeprom_remove(struct i2c_client *client)
185 {
186 struct eeprom_data *eeprom = i2c_get_clientdata(client);
187
188 i2c_slave_unregister(client);
189 sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
190
191 return 0;
192 }
193
194 static const struct i2c_device_id i2c_slave_eeprom_id[] = {
195 { "slave-24c02", I2C_SLAVE_DEVICE_MAGIC(2048 / 8, 0) },
196 { "slave-24c02ro", I2C_SLAVE_DEVICE_MAGIC(2048 / 8, I2C_SLAVE_FLAG_RO) },
197 { "slave-24c32", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16) },
198 { "slave-24c32ro", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },
199 { "slave-24c64", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16) },
200 { "slave-24c64ro", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },
201 { "slave-24c512", I2C_SLAVE_DEVICE_MAGIC(524288 / 8, I2C_SLAVE_FLAG_ADDR16) },
202 { "slave-24c512ro", I2C_SLAVE_DEVICE_MAGIC(524288 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },
203 { }
204 };
205 MODULE_DEVICE_TABLE(i2c, i2c_slave_eeprom_id);
206
207 static struct i2c_driver i2c_slave_eeprom_driver = {
208 .driver = {
209 .name = "i2c-slave-eeprom",
210 },
211 .probe = i2c_slave_eeprom_probe,
212 .remove = i2c_slave_eeprom_remove,
213 .id_table = i2c_slave_eeprom_id,
214 };
215 module_i2c_driver(i2c_slave_eeprom_driver);
216
217 MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
218 MODULE_DESCRIPTION("I2C slave mode EEPROM simulator");
219 MODULE_LICENSE("GPL v2");
220