drivers/i2c/i2c-slave-eeprom.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * I2C slave mode EEPROM simulator
0004  *
0005  * Copyright (C) 2014 by Wolfram Sang, Sang Engineering <wsa@sang-engineering.com>
0006  * Copyright (C) 2014 by Renesas Electronics Corporation
0007  *
0008  * Because most slave IP cores can only detect one I2C slave address anyhow,
0009  * this driver does not support simulating EEPROM types which take more than
0010  * one address.
0011  */
0012
0013 /*
0014  * FIXME: What to do if only 8 bits of a 16 bit address are sent?
0015  * The ST-M24C64 sends only 0xff then. Needs verification with other
0016  * EEPROMs, though. We currently use the 8 bit as a valid address.
0017  */
0018
0019 #include <linux/bitfield.h>
0020 #include <linux/firmware.h>
0021 #include <linux/i2c.h>
0022 #include <linux/init.h>
0023 #include <linux/module.h>
0024 #include <linux/of.h>
0025 #include <linux/slab.h>
0026 #include <linux/spinlock.h>
0027 #include <linux/sysfs.h>
0028
0029 struct eeprom_data {
0030     struct bin_attribute bin;
0031     spinlock_t buffer_lock;
0032     u16 buffer_idx;
0033     u16 address_mask;
0034     u8 num_address_bytes;
0035     u8 idx_write_cnt;
0036     bool read_only;
0037     u8 buffer[];
0038 };
0039
0040 #define I2C_SLAVE_BYTELEN GENMASK(15, 0)
0041 #define I2C_SLAVE_FLAG_ADDR16 BIT(16)
0042 #define I2C_SLAVE_FLAG_RO BIT(17)
0043 #define I2C_SLAVE_DEVICE_MAGIC(_len, _flags) ((_flags) | ((_len) - 1))
0044
0045 static int i2c_slave_eeprom_slave_cb(struct i2c_client *client,
0046                      enum i2c_slave_event event, u8 *val)
0047 {
0048     struct eeprom_data *eeprom = i2c_get_clientdata(client);
0049
0050     switch (event) {
0051     case I2C_SLAVE_WRITE_RECEIVED:
0052         if (eeprom->idx_write_cnt < eeprom->num_address_bytes) {
0053             if (eeprom->idx_write_cnt == 0)
0054                 eeprom->buffer_idx = 0;
0055             eeprom->buffer_idx = *val | (eeprom->buffer_idx << 8);
0056             eeprom->idx_write_cnt++;
0057         } else {
0058             if (!eeprom->read_only) {
0059                 spin_lock(&eeprom->buffer_lock);
0060                 eeprom->buffer[eeprom->buffer_idx++ & eeprom->address_mask] = *val;
0061                 spin_unlock(&eeprom->buffer_lock);
0062             }
0063         }
0064         break;
0065
0066     case I2C_SLAVE_READ_PROCESSED:
0067         /* The previous byte made it to the bus, get next one */
0068         eeprom->buffer_idx++;
0069         fallthrough;
0070     case I2C_SLAVE_READ_REQUESTED:
0071         spin_lock(&eeprom->buffer_lock);
0072         *val = eeprom->buffer[eeprom->buffer_idx & eeprom->address_mask];
0073         spin_unlock(&eeprom->buffer_lock);
0074         /*
0075          * Do not increment buffer_idx here, because we don't know if
0076          * this byte will be actually used. Read Linux I2C slave docs
0077          * for details.
0078          */
0079         break;
0080
0081     case I2C_SLAVE_STOP:
0082     case I2C_SLAVE_WRITE_REQUESTED:
0083         eeprom->idx_write_cnt = 0;
0084         break;
0085
0086     default:
0087         break;
0088     }
0089
0090     return 0;
0091 }
0092
0093 static ssize_t i2c_slave_eeprom_bin_read(struct file *filp, struct kobject *kobj,
0094         struct bin_attribute *attr, char *buf, loff_t off, size_t count)
0095 {
0096     struct eeprom_data *eeprom;
0097     unsigned long flags;
0098
0099     eeprom = dev_get_drvdata(kobj_to_dev(kobj));
0100
0101     spin_lock_irqsave(&eeprom->buffer_lock, flags);
0102     memcpy(buf, &eeprom->buffer[off], count);
0103     spin_unlock_irqrestore(&eeprom->buffer_lock, flags);
0104
0105     return count;
0106 }
0107
0108 static ssize_t i2c_slave_eeprom_bin_write(struct file *filp, struct kobject *kobj,
0109         struct bin_attribute *attr, char *buf, loff_t off, size_t count)
0110 {
0111     struct eeprom_data *eeprom;
0112     unsigned long flags;
0113
0114     eeprom = dev_get_drvdata(kobj_to_dev(kobj));
0115
0116     spin_lock_irqsave(&eeprom->buffer_lock, flags);
0117     memcpy(&eeprom->buffer[off], buf, count);
0118     spin_unlock_irqrestore(&eeprom->buffer_lock, flags);
0119
0120     return count;
0121 }
0122
0123 static int i2c_slave_init_eeprom_data(struct eeprom_data *eeprom, struct i2c_client *client,
0124                       unsigned int size)
0125 {
0126     const struct firmware *fw;
0127     const char *eeprom_data;
0128     int ret = device_property_read_string(&client->dev, "firmware-name", &eeprom_data);
0129
0130     if (!ret) {
0131         ret = request_firmware_into_buf(&fw, eeprom_data, &client->dev,
0132                         eeprom->buffer, size);
0133         if (ret)
0134             return ret;
0135         release_firmware(fw);
0136     } else {
0137         /* An empty eeprom typically has all bits set to 1 */
0138         memset(eeprom->buffer, 0xff, size);
0139     }
0140     return 0;
0141 }
0142
0143 static int i2c_slave_eeprom_probe(struct i2c_client *client, const struct i2c_device_id *id)
0144 {
0145     struct eeprom_data *eeprom;
0146     int ret;
0147     unsigned int size = FIELD_GET(I2C_SLAVE_BYTELEN, id->driver_data) + 1;
0148     unsigned int flag_addr16 = FIELD_GET(I2C_SLAVE_FLAG_ADDR16, id->driver_data);
0149
0150     eeprom = devm_kzalloc(&client->dev, sizeof(struct eeprom_data) + size, GFP_KERNEL);
0151     if (!eeprom)
0152         return -ENOMEM;
0153
0154     eeprom->num_address_bytes = flag_addr16 ? 2 : 1;
0155     eeprom->address_mask = size - 1;
0156     eeprom->read_only = FIELD_GET(I2C_SLAVE_FLAG_RO, id->driver_data);
0157     spin_lock_init(&eeprom->buffer_lock);
0158     i2c_set_clientdata(client, eeprom);
0159
0160     ret = i2c_slave_init_eeprom_data(eeprom, client, size);
0161     if (ret)
0162         return ret;
0163
0164     sysfs_bin_attr_init(&eeprom->bin);
0165     eeprom->bin.attr.name = "slave-eeprom";
0166     eeprom->bin.attr.mode = S_IRUSR | S_IWUSR;
0167     eeprom->bin.read = i2c_slave_eeprom_bin_read;
0168     eeprom->bin.write = i2c_slave_eeprom_bin_write;
0169     eeprom->bin.size = size;
0170
0171     ret = sysfs_create_bin_file(&client->dev.kobj, &eeprom->bin);
0172     if (ret)
0173         return ret;
0174
0175     ret = i2c_slave_register(client, i2c_slave_eeprom_slave_cb);
0176     if (ret) {
0177         sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
0178         return ret;
0179     }
0180
0181     return 0;
0182 };
0183
0184 static int i2c_slave_eeprom_remove(struct i2c_client *client)
0185 {
0186     struct eeprom_data *eeprom = i2c_get_clientdata(client);
0187
0188     i2c_slave_unregister(client);
0189     sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
0190
0191     return 0;
0192 }
0193
0194 static const struct i2c_device_id i2c_slave_eeprom_id[] = {
0195     { "slave-24c02", I2C_SLAVE_DEVICE_MAGIC(2048 / 8,  0) },
0196     { "slave-24c02ro", I2C_SLAVE_DEVICE_MAGIC(2048 / 8,  I2C_SLAVE_FLAG_RO) },
0197     { "slave-24c32", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16) },
0198     { "slave-24c32ro", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },
0199     { "slave-24c64", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16) },
0200     { "slave-24c64ro", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },
0201     { "slave-24c512", I2C_SLAVE_DEVICE_MAGIC(524288 / 8, I2C_SLAVE_FLAG_ADDR16) },
0202     { "slave-24c512ro", I2C_SLAVE_DEVICE_MAGIC(524288 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },
0203     { }
0204 };
0205 MODULE_DEVICE_TABLE(i2c, i2c_slave_eeprom_id);
0206
0207 static struct i2c_driver i2c_slave_eeprom_driver = {
0208     .driver = {
0209         .name = "i2c-slave-eeprom",
0210     },
0211     .probe = i2c_slave_eeprom_probe,
0212     .remove = i2c_slave_eeprom_remove,
0213     .id_table = i2c_slave_eeprom_id,
0214 };
0215 module_i2c_driver(i2c_slave_eeprom_driver);
0216
0217 MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
0218 MODULE_DESCRIPTION("I2C slave mode EEPROM simulator");
0219 MODULE_LICENSE("GPL v2");