diff options
Diffstat (limited to 'drivers/i2c/i2c-slave-eeprom.c')
| -rw-r--r-- | drivers/i2c/i2c-slave-eeprom.c | 219 |
1 files changed, 219 insertions, 0 deletions
diff --git a/drivers/i2c/i2c-slave-eeprom.c b/drivers/i2c/i2c-slave-eeprom.c new file mode 100644 index 000000000..5c7ae421c --- /dev/null +++ b/drivers/i2c/i2c-slave-eeprom.c @@ -0,0 +1,219 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * I2C slave mode EEPROM simulator + * + * Copyright (C) 2014 by Wolfram Sang, Sang Engineering <wsa@sang-engineering.com> + * Copyright (C) 2014 by Renesas Electronics Corporation + * + * Because most slave IP cores can only detect one I2C slave address anyhow, + * this driver does not support simulating EEPROM types which take more than + * one address. + */ + +/* + * FIXME: What to do if only 8 bits of a 16 bit address are sent? + * The ST-M24C64 sends only 0xff then. Needs verification with other + * EEPROMs, though. We currently use the 8 bit as a valid address. + */ + +#include <linux/bitfield.h> +#include <linux/firmware.h> +#include <linux/i2c.h> +#include <linux/init.h> +#include <linux/module.h> +#include <linux/of.h> +#include <linux/slab.h> +#include <linux/spinlock.h> +#include <linux/sysfs.h> + +struct eeprom_data { + struct bin_attribute bin; + spinlock_t buffer_lock; + u16 buffer_idx; + u16 address_mask; + u8 num_address_bytes; + u8 idx_write_cnt; + bool read_only; + u8 buffer[]; +}; + +#define I2C_SLAVE_BYTELEN GENMASK(15, 0) +#define I2C_SLAVE_FLAG_ADDR16 BIT(16) +#define I2C_SLAVE_FLAG_RO BIT(17) +#define I2C_SLAVE_DEVICE_MAGIC(_len, _flags) ((_flags) | ((_len) - 1)) + +static int i2c_slave_eeprom_slave_cb(struct i2c_client *client, + enum i2c_slave_event event, u8 *val) +{ + struct eeprom_data *eeprom = i2c_get_clientdata(client); + + switch (event) { + case I2C_SLAVE_WRITE_RECEIVED: + if (eeprom->idx_write_cnt < eeprom->num_address_bytes) { + if (eeprom->idx_write_cnt == 0) + eeprom->buffer_idx = 0; + eeprom->buffer_idx = *val | (eeprom->buffer_idx << 8); + eeprom->idx_write_cnt++; + } else { + if (!eeprom->read_only) { + spin_lock(&eeprom->buffer_lock); + eeprom->buffer[eeprom->buffer_idx++ & eeprom->address_mask] = *val; + spin_unlock(&eeprom->buffer_lock); + } + } + break; + + case I2C_SLAVE_READ_PROCESSED: + /* The previous byte made it to the bus, get next one */ + eeprom->buffer_idx++; + fallthrough; + case I2C_SLAVE_READ_REQUESTED: + spin_lock(&eeprom->buffer_lock); + *val = eeprom->buffer[eeprom->buffer_idx & eeprom->address_mask]; + spin_unlock(&eeprom->buffer_lock); + /* + * Do not increment buffer_idx here, because we don't know if + * this byte will be actually used. Read Linux I2C slave docs + * for details. + */ + break; + + case I2C_SLAVE_STOP: + case I2C_SLAVE_WRITE_REQUESTED: + eeprom->idx_write_cnt = 0; + break; + + default: + break; + } + + return 0; +} + +static ssize_t i2c_slave_eeprom_bin_read(struct file *filp, struct kobject *kobj, + struct bin_attribute *attr, char *buf, loff_t off, size_t count) +{ + struct eeprom_data *eeprom; + unsigned long flags; + + eeprom = dev_get_drvdata(kobj_to_dev(kobj)); + + spin_lock_irqsave(&eeprom->buffer_lock, flags); + memcpy(buf, &eeprom->buffer[off], count); + spin_unlock_irqrestore(&eeprom->buffer_lock, flags); + + return count; +} + +static ssize_t i2c_slave_eeprom_bin_write(struct file *filp, struct kobject *kobj, + struct bin_attribute *attr, char *buf, loff_t off, size_t count) +{ + struct eeprom_data *eeprom; + unsigned long flags; + + eeprom = dev_get_drvdata(kobj_to_dev(kobj)); + + spin_lock_irqsave(&eeprom->buffer_lock, flags); + memcpy(&eeprom->buffer[off], buf, count); + spin_unlock_irqrestore(&eeprom->buffer_lock, flags); + + return count; +} + +static int i2c_slave_init_eeprom_data(struct eeprom_data *eeprom, struct i2c_client *client, + unsigned int size) +{ + const struct firmware *fw; + const char *eeprom_data; + int ret = device_property_read_string(&client->dev, "firmware-name", &eeprom_data); + + if (!ret) { + ret = request_firmware_into_buf(&fw, eeprom_data, &client->dev, + eeprom->buffer, size); + if (ret) + return ret; + release_firmware(fw); + } else { + /* An empty eeprom typically has all bits set to 1 */ + memset(eeprom->buffer, 0xff, size); + } + return 0; +} + +static int i2c_slave_eeprom_probe(struct i2c_client *client, const struct i2c_device_id *id) +{ + struct eeprom_data *eeprom; + int ret; + unsigned int size = FIELD_GET(I2C_SLAVE_BYTELEN, id->driver_data) + 1; + unsigned int flag_addr16 = FIELD_GET(I2C_SLAVE_FLAG_ADDR16, id->driver_data); + + eeprom = devm_kzalloc(&client->dev, sizeof(struct eeprom_data) + size, GFP_KERNEL); + if (!eeprom) + return -ENOMEM; + + eeprom->num_address_bytes = flag_addr16 ? 2 : 1; + eeprom->address_mask = size - 1; + eeprom->read_only = FIELD_GET(I2C_SLAVE_FLAG_RO, id->driver_data); + spin_lock_init(&eeprom->buffer_lock); + i2c_set_clientdata(client, eeprom); + + ret = i2c_slave_init_eeprom_data(eeprom, client, size); + if (ret) + return ret; + + sysfs_bin_attr_init(&eeprom->bin); + eeprom->bin.attr.name = "slave-eeprom"; + eeprom->bin.attr.mode = S_IRUSR | S_IWUSR; + eeprom->bin.read = i2c_slave_eeprom_bin_read; + eeprom->bin.write = i2c_slave_eeprom_bin_write; + eeprom->bin.size = size; + + ret = sysfs_create_bin_file(&client->dev.kobj, &eeprom->bin); + if (ret) + return ret; + + ret = i2c_slave_register(client, i2c_slave_eeprom_slave_cb); + if (ret) { + sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin); + return ret; + } + + return 0; +}; + +static int i2c_slave_eeprom_remove(struct i2c_client *client) +{ + struct eeprom_data *eeprom = i2c_get_clientdata(client); + + i2c_slave_unregister(client); + sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin); + + return 0; +} + +static const struct i2c_device_id i2c_slave_eeprom_id[] = { + { "slave-24c02", I2C_SLAVE_DEVICE_MAGIC(2048 / 8, 0) }, + { "slave-24c02ro", I2C_SLAVE_DEVICE_MAGIC(2048 / 8, I2C_SLAVE_FLAG_RO) }, + { "slave-24c32", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16) }, + { "slave-24c32ro", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) }, + { "slave-24c64", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16) }, + { "slave-24c64ro", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) }, + { "slave-24c512", I2C_SLAVE_DEVICE_MAGIC(524288 / 8, I2C_SLAVE_FLAG_ADDR16) }, + { "slave-24c512ro", I2C_SLAVE_DEVICE_MAGIC(524288 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) }, + { } +}; +MODULE_DEVICE_TABLE(i2c, i2c_slave_eeprom_id); + +static struct i2c_driver i2c_slave_eeprom_driver = { + .driver = { + .name = "i2c-slave-eeprom", + }, + .probe = i2c_slave_eeprom_probe, + .remove = i2c_slave_eeprom_remove, + .id_table = i2c_slave_eeprom_id, +}; +module_i2c_driver(i2c_slave_eeprom_driver); + +MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>"); +MODULE_DESCRIPTION("I2C slave mode EEPROM simulator"); +MODULE_LICENSE("GPL v2"); |