slave.c

/******************************************************************************
 *
 *  $Id$
 *
 *  Copyright (C) 2006  Florian Pose, Ingenieurgemeinschaft IgH
 *
 *  This file is part of the IgH EtherCAT Master.
 *
 *  The IgH EtherCAT Master 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; either version 2 of the
 *  License, or (at your option) any later version.
 *
 *  The IgH EtherCAT Master is distributed in the hope that it will be
 *  useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with the IgH EtherCAT Master; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 *  The right to use EtherCAT Technology is granted and comes free of
 *  charge under condition of compatibility of product made by
 *  Licensee. People intending to distribute/sell products based on the
 *  code, have to sign an agreement to guarantee that products using
 *  software based on IgH EtherCAT master stay compatible with the actual
 *  EtherCAT specification (which are released themselves as an open
 *  standard) as the (only) precondition to have the right to use EtherCAT
 *  Technology, IP and trade marks.
 *
 *****************************************************************************/

/**
   \file
   EtherCAT slave methods.
*/

/*****************************************************************************/

#include <linux/module.h>
#include <linux/delay.h>

#include "globals.h"
#include "slave.h"
#include "datagram.h"
#include "master.h"

/*****************************************************************************/

extern const ec_code_msg_t al_status_messages[];

/*****************************************************************************/

int ec_slave_fetch_categories(ec_slave_t *);
ssize_t ec_show_slave_attribute(struct kobject *, struct attribute *, char *);
ssize_t ec_store_slave_attribute(struct kobject *, struct attribute *,
                                 const char *, size_t);

/*****************************************************************************/

/** \cond */

EC_SYSFS_READ_ATTR(ring_position);
EC_SYSFS_READ_ATTR(advanced_position);
EC_SYSFS_READ_ATTR(vendor_name); // deprecated
EC_SYSFS_READ_ATTR(product_name); // deprecated
EC_SYSFS_READ_ATTR(product_desc); // deprecated
EC_SYSFS_READ_ATTR(name);
EC_SYSFS_READ_ATTR(type); // deprecated
EC_SYSFS_READ_WRITE_ATTR(state);
EC_SYSFS_READ_WRITE_ATTR(eeprom);

static struct attribute *def_attrs[] = {
    &attr_ring_position,
    &attr_advanced_position,
    &attr_vendor_name,
    &attr_product_name,
    &attr_product_desc,
    &attr_name,
    &attr_type,
    &attr_state,
    &attr_eeprom,
    NULL,
};

static struct sysfs_ops sysfs_ops = {
    .show = ec_show_slave_attribute,
    .store = ec_store_slave_attribute
};

static struct kobj_type ktype_ec_slave = {
    .release = ec_slave_clear,
    .sysfs_ops = &sysfs_ops,
    .default_attrs = def_attrs
};

/** \endcond */

/*****************************************************************************/

/**
   Slave constructor.
   \return 0 in case of success, else < 0
*/

int ec_slave_init(ec_slave_t *slave, /**< EtherCAT slave */
                  ec_master_t *master, /**< EtherCAT master */
                  uint16_t ring_position, /**< ring position */
                  uint16_t station_address /**< station address to configure */
                  )
{
    unsigned int i;

    slave->ring_position = ring_position;
    slave->station_address = station_address;

    // init kobject and add it to the hierarchy
    memset(&slave->kobj, 0x00, sizeof(struct kobject));
    kobject_init(&slave->kobj);
    slave->kobj.ktype = &ktype_ec_slave;
    slave->kobj.parent = &master->kobj;
    if (kobject_set_name(&slave->kobj, "slave%03i", slave->ring_position)) {
        EC_ERR("Failed to set kobject name.\n");
        kobject_put(&slave->kobj);
        return -1;
    }

    slave->master = master;
    slave->coupler_index = 0;
    slave->coupler_subindex = 0xFFFF;
    slave->base_type = 0;
    slave->base_revision = 0;
    slave->base_build = 0;
    slave->base_fmmu_count = 0;
    slave->base_sync_count = 0;
    slave->sii_alias = 0;
    slave->sii_vendor_id = 0;
    slave->sii_product_code = 0;
    slave->sii_revision_number = 0;
    slave->sii_serial_number = 0;
    slave->sii_rx_mailbox_offset = 0;
    slave->sii_rx_mailbox_size = 0;
    slave->sii_tx_mailbox_offset = 0;
    slave->sii_tx_mailbox_size = 0;
    slave->sii_mailbox_protocols = 0;
    slave->type = NULL;
    slave->registered = 0;
    slave->fmmu_count = 0;
    slave->eeprom_data = NULL;
    slave->eeprom_size = 0;
    slave->eeprom_group = NULL;
    slave->eeprom_image = NULL;
    slave->eeprom_order = NULL;
    slave->eeprom_name = NULL;
    slave->requested_state = EC_SLAVE_STATE_UNKNOWN;
    slave->current_state = EC_SLAVE_STATE_UNKNOWN;
    slave->error_flag = 0;
    slave->online = 1;
    slave->new_eeprom_data = NULL;
    slave->new_eeprom_size = 0;

    INIT_LIST_HEAD(&slave->eeprom_strings);
    INIT_LIST_HEAD(&slave->eeprom_syncs);
    INIT_LIST_HEAD(&slave->eeprom_pdos);
    INIT_LIST_HEAD(&slave->sdo_dictionary);
    INIT_LIST_HEAD(&slave->varsize_fields);

    for (i = 0; i < 4; i++) {
        slave->dl_link[i] = 0;
        slave->dl_loop[i] = 0;
        slave->dl_signal[i] = 0;
        slave->sii_physical_layer[i] = 0xFF;
    }

    return 0;
}

/*****************************************************************************/

/**
   Slave destructor.
*/

void ec_slave_clear(struct kobject *kobj /**< kobject of the slave */)
{
    ec_slave_t *slave;
    ec_eeprom_string_t *string, *next_str;
    ec_eeprom_sync_t *sync, *next_sync;
    ec_eeprom_pdo_t *pdo, *next_pdo;
    ec_eeprom_pdo_entry_t *entry, *next_ent;
    ec_sdo_t *sdo, *next_sdo;
    ec_sdo_entry_t *en, *next_en;
    ec_varsize_t *var, *next_var;

    slave = container_of(kobj, ec_slave_t, kobj);

    // free all string objects
    list_for_each_entry_safe(string, next_str, &slave->eeprom_strings, list) {
        list_del(&string->list);
        kfree(string);
    }

    // free all sync managers
    list_for_each_entry_safe(sync, next_sync, &slave->eeprom_syncs, list) {
        list_del(&sync->list);
        kfree(sync);
    }

    // free all PDOs
    list_for_each_entry_safe(pdo, next_pdo, &slave->eeprom_pdos, list) {
        list_del(&pdo->list);
        if (pdo->name) kfree(pdo->name);

        // free all PDO entries
        list_for_each_entry_safe(entry, next_ent, &pdo->entries, list) {
            list_del(&entry->list);
            if (entry->name) kfree(entry->name);
            kfree(entry);
        }

        kfree(pdo);
    }

    if (slave->eeprom_group) kfree(slave->eeprom_group);
    if (slave->eeprom_image) kfree(slave->eeprom_image);
    if (slave->eeprom_order) kfree(slave->eeprom_order);
    if (slave->eeprom_name) kfree(slave->eeprom_name);

    // free all SDOs
    list_for_each_entry_safe(sdo, next_sdo, &slave->sdo_dictionary, list) {
        list_del(&sdo->list);
        if (sdo->name) kfree(sdo->name);

        // free all SDO entries
        list_for_each_entry_safe(en, next_en, &sdo->entries, list) {
            list_del(&en->list);
            kfree(en);
        }
        kfree(sdo);
    }

    // free information about variable sized data fields
    list_for_each_entry_safe(var, next_var, &slave->varsize_fields, list) {
        list_del(&var->list);
        kfree(var);
    }

    if (slave->eeprom_data) kfree(slave->eeprom_data);
    if (slave->new_eeprom_data) kfree(slave->new_eeprom_data);
}

/*****************************************************************************/

/**
   Reads all necessary information from a slave.
   \return 0 in case of success, else < 0
*/

int ec_slave_fetch(ec_slave_t *slave /**< EtherCAT slave */)
{
    ec_datagram_t *datagram;
    unsigned int i;
    uint16_t dl_status;

    datagram = &slave->master->simple_datagram;

    // read base data
    if (ec_datagram_nprd(datagram, slave->station_address, 0x0000, 6))
        return -1;
    if (unlikely(ec_master_simple_io(slave->master, datagram))) {
        EC_ERR("Reading base data from slave %i failed!\n",
               slave->ring_position);
        return -1;
    }

    slave->base_type =       EC_READ_U8 (datagram->data);
    slave->base_revision =   EC_READ_U8 (datagram->data + 1);
    slave->base_build =      EC_READ_U16(datagram->data + 2);
    slave->base_fmmu_count = EC_READ_U8 (datagram->data + 4);
    slave->base_sync_count = EC_READ_U8 (datagram->data + 5);

    if (slave->base_fmmu_count > EC_MAX_FMMUS)
        slave->base_fmmu_count = EC_MAX_FMMUS;

    // read data link status
    if (ec_datagram_nprd(datagram, slave->station_address, 0x0110, 2))
        return -1;
    if (unlikely(ec_master_simple_io(slave->master, datagram))) {
        EC_ERR("Reading DL status from slave %i failed!\n",
               slave->ring_position);
        return -1;
    }

    dl_status = EC_READ_U16(datagram->data);
    for (i = 0; i < 4; i++) {
        slave->dl_link[i] = dl_status & (1 << (4 + i)) ? 1 : 0;
        slave->dl_loop[i] = dl_status & (1 << (8 + i * 2)) ? 1 : 0;
        slave->dl_signal[i] = dl_status & (1 << (9 + i * 2)) ? 1 : 0;
    }

    // read EEPROM data
    if (ec_slave_sii_read16(slave, 0x0004, &slave->sii_alias))
        return -1;
    if (ec_slave_sii_read32(slave, 0x0008, &slave->sii_vendor_id))
        return -1;
    if (ec_slave_sii_read32(slave, 0x000A, &slave->sii_product_code))
        return -1;
    if (ec_slave_sii_read32(slave, 0x000C, &slave->sii_revision_number))
        return -1;
    if (ec_slave_sii_read32(slave, 0x000E, &slave->sii_serial_number))
        return -1;
    if (ec_slave_sii_read16(slave, 0x0018, &slave->sii_rx_mailbox_offset))
        return -1;
    if (ec_slave_sii_read16(slave, 0x0019, &slave->sii_rx_mailbox_size))
        return -1;
    if (ec_slave_sii_read16(slave, 0x001A, &slave->sii_tx_mailbox_offset))
        return -1;
    if (ec_slave_sii_read16(slave, 0x001B, &slave->sii_tx_mailbox_size))
        return -1;
    if (ec_slave_sii_read16(slave, 0x001C, &slave->sii_mailbox_protocols))
        return -1;

    if (unlikely(ec_slave_fetch_categories(slave))) {
        EC_ERR("Failed to fetch category data!\n");
        return -1;
    }

    return 0;
}

/*****************************************************************************/

/**
   Reads 16 bit from the slave information interface (SII).
   \return 0 in case of success, else < 0
*/

int ec_slave_sii_read16(ec_slave_t *slave,
                        /**< EtherCAT slave */
                        uint16_t offset,
                        /**< address of the SII register to read */
                        uint16_t *target
                        /**< target memory */
                        )
{
    ec_datagram_t *datagram;
    cycles_t start, end, timeout;

    datagram = &slave->master->simple_datagram;

    // initiate read operation
    if (ec_datagram_npwr(datagram, slave->station_address, 0x502, 6))
        return -1;
    EC_WRITE_U8 (datagram->data,     0x00); // read-only access
    EC_WRITE_U8 (datagram->data + 1, 0x01); // request read operation
    EC_WRITE_U32(datagram->data + 2, offset);
    if (unlikely(ec_master_simple_io(slave->master, datagram))) {
        EC_ERR("SII-read failed on slave %i!\n", slave->ring_position);
        return -1;
    }

    start = get_cycles();
    timeout = (cycles_t) 100 * cpu_khz; // 100ms

    while (1)
    {
        udelay(10);

        if (ec_datagram_nprd(datagram, slave->station_address, 0x502, 10))
            return -1;
        if (unlikely(ec_master_simple_io(slave->master, datagram))) {
            EC_ERR("Getting SII-read status failed on slave %i!\n",
                   slave->ring_position);
            return -1;
        }

        end = get_cycles();

        // check for "busy bit"
        if (likely((EC_READ_U8(datagram->data + 1) & 0x81) == 0)) {
            *target = EC_READ_U16(datagram->data + 6);
            return 0;
        }

        if (unlikely((end - start) >= timeout)) {
            EC_ERR("SII-read. Slave %i timed out!\n", slave->ring_position);
            return -1;
        }
    }
}

/*****************************************************************************/

/**
   Reads 32 bit from the slave information interface (SII).
   \return 0 in case of success, else < 0
*/

int ec_slave_sii_read32(ec_slave_t *slave,
                        /**< EtherCAT slave */
                        uint16_t offset,
                        /**< address of the SII register to read */
                        uint32_t *target
                        /**< target memory */
                        )
{
    ec_datagram_t *datagram;
    cycles_t start, end, timeout;

    datagram = &slave->master->simple_datagram;

    // initiate read operation
    if (ec_datagram_npwr(datagram, slave->station_address, 0x502, 6))
        return -1;
    EC_WRITE_U8 (datagram->data,     0x00); // read-only access
    EC_WRITE_U8 (datagram->data + 1, 0x01); // request read operation
    EC_WRITE_U32(datagram->data + 2, offset);
    if (unlikely(ec_master_simple_io(slave->master, datagram))) {
        EC_ERR("SII-read failed on slave %i!\n", slave->ring_position);
        return -1;
    }

    start = get_cycles();
    timeout = (cycles_t) 100 * cpu_khz; // 100ms

    while (1)
    {
        udelay(10);

        if (ec_datagram_nprd(datagram, slave->station_address, 0x502, 10))
            return -1;
        if (unlikely(ec_master_simple_io(slave->master, datagram))) {
            EC_ERR("Getting SII-read status failed on slave %i!\n",
                   slave->ring_position);
            return -1;
        }

        end = get_cycles();

        // check "busy bit"
        if (likely((EC_READ_U8(datagram->data + 1) & 0x81) == 0)) {
            *target = EC_READ_U32(datagram->data + 6);
            return 0;
        }

        if (unlikely((end - start) >= timeout)) {
            EC_ERR("SII-read. Slave %i timed out!\n", slave->ring_position);
            return -1;
        }
    }
}

/*****************************************************************************/

/**
   Writes 16 bit of data to the slave information interface (SII).
   \return 0 in case of success, else < 0
*/

int ec_slave_sii_write16(ec_slave_t *slave,
                         /**< EtherCAT slave */
                         uint16_t offset,
                         /**< address of the SII register to write */
                         uint16_t value
                         /**< new value */
                         )
{
    ec_datagram_t *datagram;
    cycles_t start, end, timeout;

    datagram = &slave->master->simple_datagram;

    EC_INFO("SII-write (slave %i, offset 0x%04X, value 0x%04X)\n",
            slave->ring_position, offset, value);

    // initiate write operation
    if (ec_datagram_npwr(datagram, slave->station_address, 0x502, 8))
        return -1;
    EC_WRITE_U8 (datagram->data,     0x01); // enable write access
    EC_WRITE_U8 (datagram->data + 1, 0x02); // request write operation
    EC_WRITE_U32(datagram->data + 2, offset);
    EC_WRITE_U16(datagram->data + 6, value);
    if (unlikely(ec_master_simple_io(slave->master, datagram))) {
        EC_ERR("SII-write failed on slave %i!\n", slave->ring_position);
        return -1;
    }

    start = get_cycles();
    timeout = (cycles_t) 100 * cpu_khz; // 100ms

    while (1)
    {
        udelay(10);

        if (ec_datagram_nprd(datagram, slave->station_address, 0x502, 2))
            return -1;
        if (unlikely(ec_master_simple_io(slave->master, datagram))) {
            EC_ERR("Getting SII-write status failed on slave %i!\n",
                   slave->ring_position);
            return -1;
        }

        end = get_cycles();

        // check "busy bit"
        if (likely((EC_READ_U8(datagram->data + 1) & 0x82) == 0)) {
            if (EC_READ_U8(datagram->data + 1) & 0x40) {
                EC_ERR("SII-write failed!\n");
                return -1;
            }
            else {
                EC_INFO("SII-write succeeded!\n");
                return 0;
            }
        }

        if (unlikely((end - start) >= timeout)) {
            EC_ERR("SII-write: Slave %i timed out!\n", slave->ring_position);
            return -1;
        }
    }
}

/*****************************************************************************/

/**
   Fetches data from slave's EEPROM.
   \return 0 in case of success, else < 0
   \todo memory allocation
*/

int ec_slave_fetch_categories(ec_slave_t *slave /**< EtherCAT slave */)
{
    uint16_t word_offset, cat_type, word_count;
    uint32_t value;
    uint8_t *cat_data;
    unsigned int i;

    word_offset = 0x0040;

    if (!(cat_data = (uint8_t *) kmalloc(0x10000, GFP_ATOMIC))) {
        EC_ERR("Failed to allocate 64k bytes for category data.\n");
        return -1;
    }

    while (1) {
        // read category type
        if (ec_slave_sii_read32(slave, word_offset, &value)) {
            EC_ERR("Unable to read category header.\n");
            goto out_free;
        }

        // last category?
        if ((value & 0xFFFF) == 0xFFFF) break;

        cat_type = value & 0x7FFF;
        word_count = (value >> 16) & 0xFFFF;

        // fetch category data
        for (i = 0; i < word_count; i++) {
            if (ec_slave_sii_read32(slave, word_offset + 2 + i, &value)) {
                EC_ERR("Unable to read category data word %i.\n", i);
                goto out_free;
            }

            cat_data[i * 2]     = (value >> 0) & 0xFF;
            cat_data[i * 2 + 1] = (value >> 8) & 0xFF;

            // read second word "on the fly"
            if (i + 1 < word_count) {
                i++;
                cat_data[i * 2]     = (value >> 16) & 0xFF;
                cat_data[i * 2 + 1] = (value >> 24) & 0xFF;
            }
        }

        switch (cat_type)
        {
            case 0x000A:
                if (ec_slave_fetch_strings(slave, cat_data))
                    goto out_free;
                break;
            case 0x001E:
                if (ec_slave_fetch_general(slave, cat_data))
                    goto out_free;
                break;
            case 0x0028:
                break;
            case 0x0029:
                if (ec_slave_fetch_sync(slave, cat_data, word_count))
                    goto out_free;
                break;
            case 0x0032:
                if (ec_slave_fetch_pdo(slave, cat_data, word_count, EC_TX_PDO))
                    goto out_free;
                break;
            case 0x0033:
                if (ec_slave_fetch_pdo(slave, cat_data, word_count, EC_RX_PDO))
                    goto out_free;
                break;
            default:
                EC_WARN("Unknown category type 0x%04X in slave %i.\n",
                        cat_type, slave->ring_position);
        }

        word_offset += 2 + word_count;
    }

    kfree(cat_data);
    return 0;

 out_free:
    kfree(cat_data);
    return -1;
}

/*****************************************************************************/

/**
   Fetches data from a STRING category.
   \return 0 in case of success, else < 0
*/

int ec_slave_fetch_strings(ec_slave_t *slave, /**< EtherCAT slave */
                           const uint8_t *data /**< category data */
                           )
{
    unsigned int string_count, i;
    size_t size;
    off_t offset;
    ec_eeprom_string_t *string;

    string_count = data[0];
    offset = 1;
    for (i = 0; i < string_count; i++) {
        size = data[offset];
        // allocate memory for string structure and data at a single blow
        if (!(string = (ec_eeprom_string_t *)
              kmalloc(sizeof(ec_eeprom_string_t) + size + 1, GFP_ATOMIC))) {
            EC_ERR("Failed to allocate string memory.\n");
            return -1;
        }
        string->size = size;
        // string memory appended to string structure
        string->data = (char *) string + sizeof(ec_eeprom_string_t);
        memcpy(string->data, data + offset + 1, size);
        string->data[size] = 0x00;
        list_add_tail(&string->list, &slave->eeprom_strings);
        offset += 1 + size;
    }

    return 0;
}

/*****************************************************************************/

/**
   Fetches data from a GENERAL category.
   \return 0 in case of success, else < 0
*/

int ec_slave_fetch_general(ec_slave_t *slave, /**< EtherCAT slave */
                           const uint8_t *data /**< category data */
                           )
{
    unsigned int i;

    if (ec_slave_locate_string(slave, data[0], &slave->eeprom_group))
        return -1;
    if (ec_slave_locate_string(slave, data[1], &slave->eeprom_image))
        return -1;
    if (ec_slave_locate_string(slave, data[2], &slave->eeprom_order))
        return -1;
    if (ec_slave_locate_string(slave, data[3], &slave->eeprom_name))
        return -1;

    for (i = 0; i < 4; i++)
        slave->sii_physical_layer[i] =
            (data[4] & (0x03 << (i * 2))) >> (i * 2);

    return 0;
}

/*****************************************************************************/

/**
   Fetches data from a SYNC MANAGER category.
   \return 0 in case of success, else < 0
*/

int ec_slave_fetch_sync(ec_slave_t *slave, /**< EtherCAT slave */
                        const uint8_t *data, /**< category data */
                        size_t word_count /**< number of words */
                        )
{
    unsigned int sync_count, i;
    ec_eeprom_sync_t *sync;

    sync_count = word_count / 4; // sync manager struct is 4 words long

    for (i = 0; i < sync_count; i++, data += 8) {
        if (!(sync = (ec_eeprom_sync_t *)
              kmalloc(sizeof(ec_eeprom_sync_t), GFP_ATOMIC))) {
            EC_ERR("Failed to allocate Sync-Manager memory.\n");
            return -1;
        }

        sync->index = i;
        sync->physical_start_address = *((uint16_t *) (data + 0));
        sync->length                 = *((uint16_t *) (data + 2));
        sync->control_register       = data[4];
        sync->enable                 = data[6];

        list_add_tail(&sync->list, &slave->eeprom_syncs);
    }

    return 0;
}

/*****************************************************************************/

/**
   Fetches data from a [RT]XPDO category.
   \return 0 in case of success, else < 0
*/

int ec_slave_fetch_pdo(ec_slave_t *slave, /**< EtherCAT slave */
                       const uint8_t *data, /**< category data */
                       size_t word_count, /**< number of words */
                       ec_pdo_type_t pdo_type /**< PDO type */
                       )
{
    ec_eeprom_pdo_t *pdo;
    ec_eeprom_pdo_entry_t *entry;
    unsigned int entry_count, i;

    while (word_count >= 4) {
        if (!(pdo = (ec_eeprom_pdo_t *)
              kmalloc(sizeof(ec_eeprom_pdo_t), GFP_ATOMIC))) {
            EC_ERR("Failed to allocate PDO memory.\n");
            return -1;
        }

        INIT_LIST_HEAD(&pdo->entries);
        pdo->type = pdo_type;

        pdo->index = *((uint16_t *) data);
        entry_count = data[2];
        pdo->sync_manager = data[3];
        pdo->name = NULL;
        ec_slave_locate_string(slave, data[5], &pdo->name);

        list_add_tail(&pdo->list, &slave->eeprom_pdos);

        word_count -= 4;
        data += 8;

        for (i = 0; i < entry_count; i++) {
            if (!(entry = (ec_eeprom_pdo_entry_t *)
                  kmalloc(sizeof(ec_eeprom_pdo_entry_t), GFP_ATOMIC))) {
                EC_ERR("Failed to allocate PDO entry memory.\n");
                return -1;
            }

            entry->index = *((uint16_t *) data);
            entry->subindex = data[2];
            entry->name = NULL;
            ec_slave_locate_string(slave, data[3], &entry->name);
            entry->bit_length = data[5];

            list_add_tail(&entry->list, &pdo->entries);

            word_count -= 4;
            data += 8;
        }
    }

    return 0;
}

/*****************************************************************************/

/**
   Searches the string list for an index and allocates a new string.
   \return 0 in case of success, else < 0
   \todo documentation
*/

int ec_slave_locate_string(ec_slave_t *slave, /**< EtherCAT slave */
                           unsigned int index, /**< string index */
                           char **ptr /**< Address of the string pointer */
                           )
{
    ec_eeprom_string_t *string;
    char *err_string;

    // Erst alten Speicher freigeben
    if (*ptr) {
        kfree(*ptr);
        *ptr = NULL;
    }

    // Index 0 bedeutet "nicht belegt"
    if (!index) return 0;

    // EEPROM-String mit Index finden und kopieren
    list_for_each_entry(string, &slave->eeprom_strings, list) {
        if (--index) continue;

        if (!(*ptr = (char *) kmalloc(string->size + 1, GFP_ATOMIC))) {
            EC_ERR("Unable to allocate string memory.\n");
            return -1;
        }
        memcpy(*ptr, string->data, string->size + 1);
        return 0;
    }

    EC_WARN("String %i not found in slave %i.\n", index, slave->ring_position);

    err_string = "(string not found)";

    if (!(*ptr = (char *) kmalloc(strlen(err_string) + 1, GFP_ATOMIC))) {
        EC_ERR("Unable to allocate string memory.\n");
        return -1;
    }

    memcpy(*ptr, err_string, strlen(err_string) + 1);
    return 0;
}

/*****************************************************************************/

/**
   Acknowledges an error after a state transition.
*/

void ec_slave_state_ack(ec_slave_t *slave, /**< EtherCAT slave */
                        uint8_t state /**< previous state */
                        )
{
    ec_datagram_t *datagram;
    cycles_t start, end, timeout;

    datagram = &slave->master->simple_datagram;

    if (ec_datagram_npwr(datagram, slave->station_address, 0x0120, 2)) return;
    EC_WRITE_U16(datagram->data, state | EC_ACK);
    if (unlikely(ec_master_simple_io(slave->master, datagram))) {
        EC_WARN("Acknowledge sending failed on slave %i!\n",
                slave->ring_position);
        return;
    }

    start = get_cycles();
    timeout = (cycles_t) 100 * cpu_khz; // 100ms

    while (1) {
        udelay(100); // wait a little bit...

        if (ec_datagram_nprd(datagram, slave->station_address, 0x0130, 2))
            return;
        if (unlikely(ec_master_simple_io(slave->master, datagram))) {
            slave->current_state = EC_SLAVE_STATE_UNKNOWN;
            EC_WARN("Acknowledge checking failed on slave %i!\n",
                    slave->ring_position);
            return;
        }

        end = get_cycles();

        if (EC_READ_U8(datagram->data) == state) {
            slave->current_state = state;
            EC_INFO("Acknowleged state 0x%02X on slave %i.\n", state,
                    slave->ring_position);
            return;
        }

        if (end - start >= timeout) {
            slave->current_state = EC_SLAVE_STATE_UNKNOWN;
            EC_WARN("Failed to acknowledge state 0x%02X on slave %i"
                    " - Timeout!\n", state, slave->ring_position);
            return;
        }
    }
}

/*****************************************************************************/

/**
   Reads the AL status code of a slave and displays it.
   If the AL status code is not supported, or if no error occurred (both
   resulting in code = 0), nothing is displayed.
*/

void ec_slave_read_al_status_code(ec_slave_t *slave /**< EtherCAT slave */)
{
    ec_datagram_t *datagram;
    uint16_t code;
    const ec_code_msg_t *al_msg;

    datagram = &slave->master->simple_datagram;

    if (ec_datagram_nprd(datagram, slave->station_address, 0x0134, 2)) return;
    if (unlikely(ec_master_simple_io(slave->master, datagram))) {
        EC_WARN("Failed to read AL status code on slave %i!\n",
                slave->ring_position);
        return;
    }

    if (!(code = EC_READ_U16(datagram->data))) return;

    for (al_msg = al_status_messages; al_msg->code; al_msg++) {
        if (al_msg->code == code) {
            EC_ERR("AL status message 0x%04X: \"%s\".\n",
                   al_msg->code, al_msg->message);
            return;
        }
    }

    EC_ERR("Unknown AL status code 0x%04X.\n", code);
}

/*****************************************************************************/

/**
   Does a state transition.
   \return 0 in case of success, else < 0
*/

int ec_slave_state_change(ec_slave_t *slave, /**< EtherCAT slave */
                          uint8_t state /**< new state */
                          )
{
    ec_datagram_t *datagram;
    cycles_t start, end, timeout;

    datagram = &slave->master->simple_datagram;

    slave->requested_state = state;

    if (ec_datagram_npwr(datagram, slave->station_address, 0x0120, 2))
        return -1;
    EC_WRITE_U16(datagram->data, state);
    if (unlikely(ec_master_simple_io(slave->master, datagram))) {
        EC_ERR("Failed to set state 0x%02X on slave %i!\n",
               state, slave->ring_position);
        return -1;
    }

    start = get_cycles();
    timeout = (cycles_t) 10 * cpu_khz; // 10ms

    while (1)
    {
        udelay(100); // wait a little bit

        if (ec_datagram_nprd(datagram, slave->station_address, 0x0130, 2))
            return -1;
        if (unlikely(ec_master_simple_io(slave->master, datagram))) {
            slave->current_state = EC_SLAVE_STATE_UNKNOWN;
            EC_ERR("Failed to check state 0x%02X on slave %i!\n",
                   state, slave->ring_position);
            return -1;
        }

        end = get_cycles();

        if (unlikely(EC_READ_U8(datagram->data) & 0x10)) {
            // state change error
            EC_ERR("Failed to set state 0x%02X - Slave %i refused state change"
                   " (code 0x%02X)!\n", state, slave->ring_position,
                   EC_READ_U8(datagram->data));
            slave->current_state = EC_READ_U8(datagram->data);
            state = slave->current_state & 0x0F;
            ec_slave_read_al_status_code(slave);
            ec_slave_state_ack(slave, state);
            return -1;
        }

        if (likely(EC_READ_U8(datagram->data) == (state & 0x0F))) {
            slave->current_state = state;
            return 0; // state change successful
        }

        if (unlikely((end - start) >= timeout)) {
            slave->current_state = EC_SLAVE_STATE_UNKNOWN;
            EC_ERR("Failed to check state 0x%02X of slave %i - Timeout!\n",
                   state, slave->ring_position);
            return -1;
        }
    }
}

/*****************************************************************************/

/**
   Prepares an FMMU configuration.
   Configuration data for the FMMU is saved in the slave structure and is
   written to the slave in ecrt_master_activate().