mm/memory.c: fix race when faulting a device private page
[platform/kernel/linux-starfive.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 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
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(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
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
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
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
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");