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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
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
76
77
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
138 memset(eeprom->buffer, 0xff, size);
139 }
140 return 0;
141}
142
143static 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
184static 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
194static 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};
205MODULE_DEVICE_TABLE(i2c, i2c_slave_eeprom_id);
206
207static 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};
215module_i2c_driver(i2c_slave_eeprom_driver);
216
217MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
218MODULE_DESCRIPTION("I2C slave mode EEPROM simulator");
219MODULE_LICENSE("GPL v2");
220
