i2c: slave-eeprom: Add read only mode
[sfrench/cifs-2.6.git] / drivers / i2c / i2c-slave-eeprom.c
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 IP blocks can only detect one I2C slave address anyhow, this
9  * driver does not support simulating EEPROM types which take more than one
10  * address. It is prepared to simulate bigger EEPROMs with an internal 16 bit
11  * pointer, yet implementation is deferred until the need actually arises.
12  */
13
14 /*
15  * FIXME: What to do if only 8 bits of a 16 bit address are sent?
16  * The ST-M24C64 sends only 0xff then. Needs verification with other
17  * EEPROMs, though. We currently use the 8 bit as a valid address.
18  */
19
20 #include <linux/bitfield.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))
44
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
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(container_of(kobj, struct device, 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
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(container_of(kobj, struct device, 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
123 static int i2c_slave_eeprom_probe(struct i2c_client *client, const struct i2c_device_id *id)
124 {
125         struct eeprom_data *eeprom;
126         int ret;
127         unsigned int size = FIELD_GET(I2C_SLAVE_BYTELEN, id->driver_data);
128         unsigned int flag_addr16 = FIELD_GET(I2C_SLAVE_FLAG_ADDR16, id->driver_data);
129
130         eeprom = devm_kzalloc(&client->dev, sizeof(struct eeprom_data) + size, GFP_KERNEL);
131         if (!eeprom)
132                 return -ENOMEM;
133
134         eeprom->idx_write_cnt = 0;
135         eeprom->num_address_bytes = flag_addr16 ? 2 : 1;
136         eeprom->address_mask = size - 1;
137         eeprom->read_only = FIELD_GET(I2C_SLAVE_FLAG_RO, id->driver_data);
138         spin_lock_init(&eeprom->buffer_lock);
139         i2c_set_clientdata(client, eeprom);
140
141         sysfs_bin_attr_init(&eeprom->bin);
142         eeprom->bin.attr.name = "slave-eeprom";
143         eeprom->bin.attr.mode = S_IRUSR | S_IWUSR;
144         eeprom->bin.read = i2c_slave_eeprom_bin_read;
145         eeprom->bin.write = i2c_slave_eeprom_bin_write;
146         eeprom->bin.size = size;
147
148         ret = sysfs_create_bin_file(&client->dev.kobj, &eeprom->bin);
149         if (ret)
150                 return ret;
151
152         ret = i2c_slave_register(client, i2c_slave_eeprom_slave_cb);
153         if (ret) {
154                 sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
155                 return ret;
156         }
157
158         return 0;
159 };
160
161 static int i2c_slave_eeprom_remove(struct i2c_client *client)
162 {
163         struct eeprom_data *eeprom = i2c_get_clientdata(client);
164
165         i2c_slave_unregister(client);
166         sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
167
168         return 0;
169 }
170
171 static const struct i2c_device_id i2c_slave_eeprom_id[] = {
172         { "slave-24c02", I2C_SLAVE_DEVICE_MAGIC(2048 / 8,  0) },
173         { "slave-24c02ro", I2C_SLAVE_DEVICE_MAGIC(2048 / 8,  I2C_SLAVE_FLAG_RO) },
174         { "slave-24c32", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16) },
175         { "slave-24c32ro", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },
176         { "slave-24c64", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16) },
177         { "slave-24c64ro", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },
178         { }
179 };
180 MODULE_DEVICE_TABLE(i2c, i2c_slave_eeprom_id);
181
182 static struct i2c_driver i2c_slave_eeprom_driver = {
183         .driver = {
184                 .name = "i2c-slave-eeprom",
185         },
186         .probe = i2c_slave_eeprom_probe,
187         .remove = i2c_slave_eeprom_remove,
188         .id_table = i2c_slave_eeprom_id,
189 };
190 module_i2c_driver(i2c_slave_eeprom_driver);
191
192 MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
193 MODULE_DESCRIPTION("I2C slave mode EEPROM simulator");
194 MODULE_LICENSE("GPL v2");