linux-imx

/*

 * 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;