diff options
Diffstat (limited to 'drivers/i2c/i2c-slave-eeprom.c')
| -rw-r--r-- | drivers/i2c/i2c-slave-eeprom.c | 169 |
1 files changed, 169 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..b2039f94c --- /dev/null +++ b/drivers/i2c/i2c-slave-eeprom.c @@ -0,0 +1,169 @@ +/* + * I2C slave mode EEPROM simulator + * + * Copyright (C) 2014 by Wolfram Sang, Sang Engineering <wsa@sang-engineering.com> + * Copyright (C) 2014 by Renesas Electronics Corporation + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License as published by the + * Free Software Foundation; version 2 of the License. + * + * Because most IP blocks can only detect one I2C slave address anyhow, this + * driver does not support simulating EEPROM types which take more than one + * address. It is prepared to simulate bigger EEPROMs with an internal 16 bit + * pointer, yet implementation is deferred until the need actually arises. + */ + +#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; + bool first_write; + spinlock_t buffer_lock; + u8 buffer_idx; + u8 buffer[]; +}; + +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->first_write) { + eeprom->buffer_idx = *val; + eeprom->first_write = false; + } else { + spin_lock(&eeprom->buffer_lock); + eeprom->buffer[eeprom->buffer_idx++] = *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]; + 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->first_write = true; + 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(container_of(kobj, struct device, 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(container_of(kobj, struct device, 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_eeprom_probe(struct i2c_client *client, const struct i2c_device_id *id) +{ + struct eeprom_data *eeprom; + int ret; + unsigned size = id->driver_data; + + eeprom = devm_kzalloc(&client->dev, sizeof(struct eeprom_data) + size, GFP_KERNEL); + if (!eeprom) + return -ENOMEM; + + eeprom->first_write = true; + spin_lock_init(&eeprom->buffer_lock); + i2c_set_clientdata(client, eeprom); + + 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", 2048 / 8 }, + { } +}; +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"); |