fsm_slave_scan.c

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/*****************************************************************************
 *
 *  Copyright (C) 2006-2026  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 version 2, as
 *  published by the Free Software Foundation.
 *
 *  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
 *
 ****************************************************************************/

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

#include "globals.h"
#include "master.h"
#include "mailbox.h"
#include "slave_config.h"

#include "fsm_slave_scan.h"

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

// prototypes for private methods
int ec_fsm_slave_scan_running(const ec_fsm_slave_scan_t *);
void ec_fsm_slave_scan_enter_sii_size(ec_fsm_slave_scan_t *);
void ec_fsm_slave_scan_enter_assign_sii(ec_fsm_slave_scan_t *);
void ec_fsm_slave_scan_enter_sii_ident(ec_fsm_slave_scan_t *);
void ec_fsm_slave_scan_enter_datalink(ec_fsm_slave_scan_t *);
#ifdef EC_REGALIAS
void ec_fsm_slave_scan_enter_regalias(ec_fsm_slave_scan_t *);
#endif
void ec_fsm_slave_scan_enter_preop(ec_fsm_slave_scan_t *);
void ec_fsm_slave_scan_enter_clear_mailbox(ec_fsm_slave_scan_t *);
void ec_fsm_slave_scan_enter_pdos(ec_fsm_slave_scan_t *);

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

void ec_fsm_slave_scan_state_start(ec_fsm_slave_scan_t *);
void ec_fsm_slave_scan_state_address(ec_fsm_slave_scan_t *);
void ec_fsm_slave_scan_state_state(ec_fsm_slave_scan_t *);
void ec_fsm_slave_scan_state_base(ec_fsm_slave_scan_t *);
void ec_fsm_slave_scan_state_dc_cap(ec_fsm_slave_scan_t *);
void ec_fsm_slave_scan_state_dc_times(ec_fsm_slave_scan_t *);
void ec_fsm_slave_scan_state_datalink(ec_fsm_slave_scan_t *);
#ifdef EC_SII_ASSIGN
void ec_fsm_slave_scan_state_assign_sii(ec_fsm_slave_scan_t *);
#endif
void ec_fsm_slave_scan_state_sii_ident(ec_fsm_slave_scan_t *);
void ec_fsm_slave_scan_state_sii_size(ec_fsm_slave_scan_t *);
void ec_fsm_slave_scan_state_sii_data(ec_fsm_slave_scan_t *);
void ec_fsm_slave_scan_state_mailbox_cleared(ec_fsm_slave_scan_t *);
#ifdef EC_REGALIAS
void ec_fsm_slave_scan_state_regalias(ec_fsm_slave_scan_t *);
#endif
void ec_fsm_slave_scan_state_preop(ec_fsm_slave_scan_t *);
void ec_fsm_slave_scan_state_sync(ec_fsm_slave_scan_t *);
void ec_fsm_slave_scan_state_pdos(ec_fsm_slave_scan_t *);

void ec_fsm_slave_scan_state_end(ec_fsm_slave_scan_t *);
void ec_fsm_slave_scan_state_error(ec_fsm_slave_scan_t *);

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

void ec_fsm_slave_scan_init(
        ec_fsm_slave_scan_t *fsm, 
        ec_datagram_t *datagram, 
        ec_fsm_slave_config_t *fsm_slave_config, 
        ec_fsm_pdo_t *fsm_pdo 
        )
{
    fsm->slave = NULL;
    fsm->datagram = datagram;
    fsm->fsm_slave_config = fsm_slave_config;
    fsm->fsm_pdo = fsm_pdo;

    fsm->retries = 0;
    fsm->state = NULL;
    fsm->sii_offset = 0;

    // init sub state machines
    ec_fsm_sii_init(&fsm->fsm_sii, fsm->datagram);
}

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

void ec_fsm_slave_scan_clear(
        ec_fsm_slave_scan_t *fsm 
        )
{
    // clear sub state machines
    ec_fsm_sii_clear(&fsm->fsm_sii);
}

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

void ec_fsm_slave_scan_start(
        ec_fsm_slave_scan_t *fsm, 
        ec_slave_t *slave 
        )
{
    fsm->slave = slave;
    fsm->state = ec_fsm_slave_scan_state_start;
}

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

int ec_fsm_slave_scan_running(
        const ec_fsm_slave_scan_t *fsm 
        )
{
    return fsm->state != ec_fsm_slave_scan_state_end
        && fsm->state != ec_fsm_slave_scan_state_error;
}

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

int ec_fsm_slave_scan_exec(
        ec_fsm_slave_scan_t *fsm 
        )
{
    if (fsm->datagram->state == EC_DATAGRAM_SENT
        || fsm->datagram->state == EC_DATAGRAM_QUEUED) {
        // datagram was not sent or received yet.
        return ec_fsm_slave_scan_running(fsm);
    }

    fsm->state(fsm);
    return ec_fsm_slave_scan_running(fsm);
}

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

int ec_fsm_slave_scan_success(
        const ec_fsm_slave_scan_t *fsm 
        )
{
    return fsm->state == ec_fsm_slave_scan_state_end;
}

/*****************************************************************************
 *  slave scan state machine
 ****************************************************************************/

void ec_fsm_slave_scan_state_start(
        ec_fsm_slave_scan_t *fsm 
        )
{
    // write station address
    ec_datagram_apwr(fsm->datagram, fsm->slave->ring_position, 0x0010, 2);
    EC_WRITE_U16(fsm->datagram->data, fsm->slave->station_address);
    fsm->retries = EC_FSM_RETRIES;
    fsm->state = ec_fsm_slave_scan_state_address;
}

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

void ec_fsm_slave_scan_state_address(
        ec_fsm_slave_scan_t *fsm 
        )
{
    ec_datagram_t *datagram = fsm->datagram;

    if (datagram->state == EC_DATAGRAM_TIMED_OUT && fsm->retries--)
        return;

    if (datagram->state != EC_DATAGRAM_RECEIVED) {
        fsm->state = ec_fsm_slave_scan_state_error;
        EC_SLAVE_ERR(fsm->slave,
                "Failed to receive station address datagram: ");
        ec_datagram_print_state(datagram);
        return;
    }

    if (datagram->working_counter != 1) {
        fsm->slave->error_flag = 1;
        fsm->state = ec_fsm_slave_scan_state_error;
        EC_SLAVE_ERR(fsm->slave, "Failed to write station address: ");
        ec_datagram_print_wc_error(datagram);
        return;
    }

    // Read AL state
    ec_datagram_fprd(datagram, fsm->slave->station_address, 0x0130, 2);
    ec_datagram_zero(datagram);
    fsm->retries = EC_FSM_RETRIES;
    fsm->state = ec_fsm_slave_scan_state_state;
}

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

void ec_fsm_slave_scan_state_state(
        ec_fsm_slave_scan_t *fsm 
        )
{
    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_t *slave = fsm->slave;

    if (datagram->state == EC_DATAGRAM_TIMED_OUT && fsm->retries--)
        return;

    if (datagram->state != EC_DATAGRAM_RECEIVED) {
        fsm->state = ec_fsm_slave_scan_state_error;
        EC_SLAVE_ERR(slave, "Failed to receive AL state datagram: ");
        ec_datagram_print_state(datagram);
        return;
    }

    if (datagram->working_counter != 1) {
        fsm->slave->error_flag = 1;
        fsm->state = ec_fsm_slave_scan_state_error;
        EC_SLAVE_ERR(slave, "Failed to read AL state: ");
        ec_datagram_print_wc_error(datagram);
        return;
    }

    slave->current_state = EC_READ_U8(datagram->data);
    if (slave->current_state & EC_SLAVE_STATE_ACK_ERR) {
        char state_str[EC_STATE_STRING_SIZE];
        ec_state_string(slave->current_state, state_str, 0);
        EC_SLAVE_WARN(slave, "Slave has state error bit set (%s)!\n",
                state_str);
    }

    // read base data
    ec_datagram_fprd(datagram, fsm->slave->station_address, 0x0000, 12);
    ec_datagram_zero(datagram);
    fsm->retries = EC_FSM_RETRIES;
    fsm->state = ec_fsm_slave_scan_state_base;
}

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

void ec_fsm_slave_scan_state_base(
        ec_fsm_slave_scan_t *fsm 
        )
{
    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_t *slave = fsm->slave;
    u8 octet;
    int i;

    if (datagram->state == EC_DATAGRAM_TIMED_OUT && fsm->retries--)
        return;

    if (datagram->state != EC_DATAGRAM_RECEIVED) {
        fsm->state = ec_fsm_slave_scan_state_error;
        EC_SLAVE_ERR(slave, "Failed to receive base data datagram: ");
        ec_datagram_print_state(datagram);
        return;
    }

    if (datagram->working_counter != 1) {
        fsm->slave->error_flag = 1;
        fsm->state = ec_fsm_slave_scan_state_error;
        EC_SLAVE_ERR(slave, "Failed to read base data: ");
        ec_datagram_print_wc_error(datagram);
        return;
    }

    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);
    if (slave->base_fmmu_count > EC_MAX_FMMUS) {
        EC_SLAVE_WARN(slave, "Slave has more FMMUs (%u) than the master can"
                " handle (%u).\n", slave->base_fmmu_count, EC_MAX_FMMUS);
        slave->base_fmmu_count = EC_MAX_FMMUS;
    }

    slave->base_sync_count = EC_READ_U8(datagram->data + 5);
    if (slave->base_sync_count > EC_MAX_SYNC_MANAGERS) {
        EC_SLAVE_WARN(slave, "Slave provides more sync managers (%u)"
                " than the master can handle (%u).\n",
                slave->base_sync_count, EC_MAX_SYNC_MANAGERS);
        slave->base_sync_count = EC_MAX_SYNC_MANAGERS;
    }

    octet = EC_READ_U8(datagram->data + 7);
    for (i = 0; i < EC_MAX_PORTS; i++) {
        slave->ports[i].desc = (octet >> (2 * i)) & 0x03;
    }

    octet = EC_READ_U8(datagram->data + 8);
    slave->base_fmmu_bit_operation = octet & 0x01;
    slave->base_dc_supported = (octet >> 2) & 0x01;
    slave->base_dc_range = ((octet >> 3) & 0x01) ? EC_DC_64 : EC_DC_32;

    if (slave->base_dc_supported) {
        // read DC capabilities
        ec_datagram_fprd(datagram, slave->station_address, 0x0910,
                slave->base_dc_range == EC_DC_64 ? 8 : 4);
        ec_datagram_zero(datagram);
        fsm->retries = EC_FSM_RETRIES;
        fsm->state = ec_fsm_slave_scan_state_dc_cap;
    } else {
        ec_fsm_slave_scan_enter_datalink(fsm);
    }
}

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

void ec_fsm_slave_scan_state_dc_cap(
        ec_fsm_slave_scan_t *fsm 
        )
{
    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_t *slave = fsm->slave;

    if (datagram->state == EC_DATAGRAM_TIMED_OUT && fsm->retries--)
        return;

    if (datagram->state != EC_DATAGRAM_RECEIVED) {
        fsm->state = ec_fsm_slave_scan_state_error;
        EC_SLAVE_ERR(slave, "Failed to receive system time datagram: ");
        ec_datagram_print_state(datagram);
        return;
    }

    if (datagram->working_counter == 1) {
        slave->has_dc_system_time = 1;
        EC_SLAVE_DBG(slave, 1, "Slave has the System Time register.\n");
    } else if (datagram->working_counter == 0) {
        EC_SLAVE_DBG(slave, 1, "Slave has no System Time register; delay "
                "measurement only.\n");
    } else {
        fsm->slave->error_flag = 1;
        fsm->state = ec_fsm_slave_scan_state_error;
        EC_SLAVE_ERR(slave, "Failed to determine, if system time register is "
                "supported: ");
        ec_datagram_print_wc_error(datagram);
        return;
    }

    // read DC port receive times
    ec_datagram_fprd(datagram, slave->station_address, 0x0900, 16);
    ec_datagram_zero(datagram);
    fsm->retries = EC_FSM_RETRIES;
    fsm->state = ec_fsm_slave_scan_state_dc_times;
}

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

void ec_fsm_slave_scan_state_dc_times(
        ec_fsm_slave_scan_t *fsm 
        )
{
    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_t *slave = fsm->slave;
    int i;

    if (datagram->state == EC_DATAGRAM_TIMED_OUT && fsm->retries--)
        return;

    if (datagram->state != EC_DATAGRAM_RECEIVED) {
        fsm->state = ec_fsm_slave_scan_state_error;
        EC_SLAVE_ERR(slave, "Failed to receive system time datagram: ");
        ec_datagram_print_state(datagram);
        return;
    }

    if (datagram->working_counter != 1) {
        fsm->slave->error_flag = 1;
        fsm->state = ec_fsm_slave_scan_state_error;
        EC_SLAVE_ERR(slave, "Failed to get DC receive times: ");
        ec_datagram_print_wc_error(datagram);
        return;
    }

    for (i = 0; i < EC_MAX_PORTS; i++) {
        slave->ports[i].receive_time = EC_READ_U32(datagram->data + 4 * i);
    }

    ec_fsm_slave_scan_enter_datalink(fsm);
}

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

void ec_fsm_slave_scan_enter_datalink(
        ec_fsm_slave_scan_t *fsm 
        )
{
    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_t *slave = fsm->slave;

    // read data link status
    ec_datagram_fprd(datagram, slave->station_address, 0x0110, 2);
    ec_datagram_zero(datagram);
    fsm->retries = EC_FSM_RETRIES;
    fsm->state = ec_fsm_slave_scan_state_datalink;
}

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

void ec_fsm_slave_scan_enter_sii_size(
        ec_fsm_slave_scan_t *fsm 
        )
{
    // Start fetching SII size

    EC_SLAVE_DBG(fsm->slave, 1, "Determining SII size.\n");

    fsm->sii_offset = EC_FIRST_SII_CATEGORY_OFFSET; // first category header
    ec_fsm_sii_read(&fsm->fsm_sii, fsm->slave, fsm->sii_offset,
            EC_FSM_SII_USE_CONFIGURED_ADDRESS);
    fsm->state = ec_fsm_slave_scan_state_sii_size;
    fsm->state(fsm); // execute state immediately
}

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

#ifdef EC_SII_ASSIGN

void ec_fsm_slave_scan_enter_assign_sii(
        ec_fsm_slave_scan_t *fsm 
        )
{
    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_t *slave = fsm->slave;

    EC_SLAVE_DBG(slave, 1, "Assigning SII access to EtherCAT.\n");

    // assign SII to ECAT
    ec_datagram_fpwr(datagram, slave->station_address, 0x0500, 1);
    EC_WRITE_U8(datagram->data, 0x00); // EtherCAT
    fsm->retries = EC_FSM_RETRIES;
    fsm->state = ec_fsm_slave_scan_state_assign_sii;
}

#endif

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

void ec_fsm_slave_scan_enter_sii_ident(
        ec_fsm_slave_scan_t *fsm 
        )
{
    // Start fetching identification (alias/vendor/product/revision/serial)
    // to check for possible SII cache hits

    EC_SLAVE_DBG(fsm->slave, 1, "Loading SII identification words.\n");

    fsm->sii_offset = EC_SII_WORD_OFFSET_ALIAS;
    ec_fsm_sii_read(&fsm->fsm_sii, fsm->slave, fsm->sii_offset,
            EC_FSM_SII_USE_CONFIGURED_ADDRESS);
    fsm->state = ec_fsm_slave_scan_state_sii_ident;
    fsm->state(fsm); // execute state immediately
}

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

void ec_fsm_slave_scan_state_datalink(
        ec_fsm_slave_scan_t *fsm 
        )
{
    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_t *slave = fsm->slave;
    uint16_t dl_status;
    unsigned int i;

    if (datagram->state == EC_DATAGRAM_TIMED_OUT && fsm->retries--)
        return;

    if (datagram->state != EC_DATAGRAM_RECEIVED) {
        fsm->state = ec_fsm_slave_scan_state_error;
        EC_SLAVE_ERR(slave, "Failed to receive DL status datagram: ");
        ec_datagram_print_state(datagram);
        return;
    }

    if (datagram->working_counter != 1) {
        fsm->slave->error_flag = 1;
        fsm->state = ec_fsm_slave_scan_state_error;
        EC_SLAVE_ERR(slave, "Failed to read DL status: ");
        ec_datagram_print_wc_error(datagram);
        return;
    }

    dl_status = EC_READ_U16(datagram->data);
    for (i = 0; i < EC_MAX_PORTS; i++) {
        slave->ports[i].link.link_up =
            dl_status & (1 << (4 + i)) ? 1 : 0;
        slave->ports[i].link.loop_closed =
            dl_status & (1 << (8 + i * 2)) ? 1 : 0;
        slave->ports[i].link.signal_detected =
            dl_status & (1 << (9 + i * 2)) ? 1 : 0;
    }

#ifdef EC_SII_ASSIGN
    ec_fsm_slave_scan_enter_assign_sii(fsm);
#else
    if (fsm->slave->master->sii_caching != EC_SII_DISABLE_CACHING) {
        ec_fsm_slave_scan_enter_sii_ident(fsm);
    }
    else {
        ec_fsm_slave_scan_enter_sii_size(fsm);
    }
#endif
}

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

#ifdef EC_SII_ASSIGN

void ec_fsm_slave_scan_state_assign_sii(
        ec_fsm_slave_scan_t *fsm 
        )
{
    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_t *slave = fsm->slave;

    if (datagram->state == EC_DATAGRAM_TIMED_OUT && fsm->retries--) {
        return;
    }

    if (datagram->state != EC_DATAGRAM_RECEIVED) {
        EC_SLAVE_WARN(slave, "Failed to receive SII assignment datagram: ");
        ec_datagram_print_state(datagram);
        // Try to go on, probably assignment is correct
        goto continue_with_sii_size;
    }

    if (datagram->working_counter != 1) {
        EC_SLAVE_WARN(slave, "Failed to assign SII to EtherCAT: ");
        ec_datagram_print_wc_error(datagram);
        // Try to go on, probably assignment is correct
    }

continue_with_sii_size:
    if (fsm->slave->master->sii_caching != EC_SII_DISABLE_CACHING) {
        ec_fsm_slave_scan_enter_sii_ident(fsm);
    }
    else {
        ec_fsm_slave_scan_enter_sii_size(fsm);
    }
}

#endif

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

void ec_fsm_slave_scan_state_sii_ident(
        ec_fsm_slave_scan_t *fsm 
        )
{
    ec_slave_t *slave = fsm->slave;
    unsigned int words_fitting;
    int words_to_copy;
    uint32_t vendor, product, revision, serial;
    ec_sii_page_t *cached;

    if (ec_fsm_sii_exec(&fsm->fsm_sii)) {
        return;
    }

    if (!ec_fsm_sii_success(&fsm->fsm_sii)) {
        fsm->slave->error_flag = 1;
        fsm->state = ec_fsm_slave_scan_state_error;
        EC_SLAVE_ERR(slave, "Failed to fetch SII identification.\n");
        return;
    }

    if (fsm->sii_offset == EC_SII_WORD_OFFSET_ALIAS) {
        // First step: Fetch alias from 0x0004, then go to 0x0008
        // unfortunately it makes no sense to read through, if only 2 words
        // are read in parallel (depends on the slave)
        slave->sii.alias = EC_READ_U16(fsm->fsm_sii.value);
        slave->effective_alias = slave->sii.alias;

        EC_SLAVE_DBG(slave, 1, "Alias %u\n", slave->sii.alias);

        // Continue with vendor ID
        fsm->sii_offset = EC_SII_WORD_OFFSET_VENDOR;
        ec_fsm_sii_read(&fsm->fsm_sii, slave, fsm->sii_offset,
                        EC_FSM_SII_USE_CONFIGURED_ADDRESS);
        ec_fsm_sii_exec(&fsm->fsm_sii); // execute state immediately
        return;
    }

    // Vendor ID and following
    words_fitting = EC_NUM_SII_IDENT_WORDS + EC_SII_WORD_OFFSET_VENDOR
        - fsm->sii_offset;
    words_to_copy = min(words_fitting, fsm->fsm_sii.read_word_count);
    memcpy(fsm->sii_ident + (fsm->sii_offset - EC_SII_WORD_OFFSET_VENDOR) * 2,
                    fsm->fsm_sii.value, words_to_copy * 2);

    if (fsm->sii_offset - EC_SII_WORD_OFFSET_VENDOR
            + fsm->fsm_sii.read_word_count < EC_NUM_SII_IDENT_WORDS) {
        // fetch the remaining words
        fsm->sii_offset += fsm->fsm_sii.read_word_count;
        ec_fsm_sii_read(&fsm->fsm_sii, slave, fsm->sii_offset,
                EC_FSM_SII_USE_CONFIGURED_ADDRESS);
        ec_fsm_sii_exec(&fsm->fsm_sii); // execute state immediately
        return;
    }

    // All identification words read

    vendor = EC_READ_U32(fsm->sii_ident);
    product = EC_READ_U32(fsm->sii_ident + 4);
    revision = EC_READ_U32(fsm->sii_ident + 8);
    serial = EC_READ_U32(fsm->sii_ident + 12);

    EC_SLAVE_DBG(slave, 1,
            "Identification 0x%08X / 0x%08X / 0x%08X / 0x%08X\n",
            vendor, product, revision, serial);

    cached = ec_master_find_cached_sii_page(slave->master, vendor,
            product, revision, serial, slave->sii.alias);
    if (cached) {
        int ret;

        EC_SLAVE_DBG(slave, 1, "Found matching SII page in cache.\n");

        ret = ec_sii_page_copy(&slave->sii_page, cached);
        if (ret) {
            EC_SLAVE_ERR(slave, "Failed to copy cached SII page.\n");
            fsm->slave->error_flag = 1;
            fsm->state = ec_fsm_slave_scan_state_error;
            return;
        }

        slave->sii_page.origin = EC_SII_PAGE_CACHED;

        // Evaluate the (cached) SII contents...
        if (ec_slave_analyze_sii_data(slave)) {
            EC_SLAVE_ERR(slave, "Failed to analyze category data.\n");
            fsm->slave->error_flag = 1;
            fsm->state = ec_fsm_slave_scan_state_error;
            return;
        }

#ifdef EC_REGALIAS
        ec_fsm_slave_scan_enter_regalias(fsm);
#else
        if (slave->sii.mailbox_protocols & EC_MBOX_COE) {
            ec_fsm_slave_scan_enter_preop(fsm);
        } else {
            fsm->state = ec_fsm_slave_scan_state_end;
        }
#endif
        return;
    }

    EC_SLAVE_DBG(slave, 1, "No matching SII page found in cache.\n");
    // We will have to read it out by ourselves. Sigh...
    ec_fsm_slave_scan_enter_sii_size(fsm);
}

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

void ec_fsm_slave_scan_state_sii_size(
        ec_fsm_slave_scan_t *fsm 
        )
{
    ec_slave_t *slave = fsm->slave;
    uint16_t cat_type, cat_size;
    size_t word_count = 0;

    if (ec_fsm_sii_exec(&fsm->fsm_sii))
        return;

    if (!ec_fsm_sii_success(&fsm->fsm_sii)) {
        fsm->slave->error_flag = 1;
        fsm->state = ec_fsm_slave_scan_state_error;
        EC_SLAVE_ERR(slave, "Failed to determine SII content size:"
                " Reading word offset 0x%04x failed. Assuming %u words.\n",
                fsm->sii_offset, EC_FIRST_SII_CATEGORY_OFFSET);
        word_count = EC_FIRST_SII_CATEGORY_OFFSET;
        goto alloc_sii;
    }

    cat_type = EC_READ_U16(fsm->fsm_sii.value);
    cat_size = EC_READ_U16(fsm->fsm_sii.value + 2);

    if (cat_type != 0xFFFF) { // not the last category
        off_t next_offset = 2UL + fsm->sii_offset + cat_size;

        EC_SLAVE_DBG(slave, 1, "Found category type %u with size %u."
                " Proceeding to offset %zd.\n",
                cat_type, cat_size, (ssize_t)next_offset);

        if (next_offset >= EC_MAX_SII_SIZE) {
            EC_SLAVE_WARN(slave, "SII size exceeds %u words"
                    " (0xffff limiter missing?).\n", EC_MAX_SII_SIZE);
            // cut off category data...
            word_count = EC_FIRST_SII_CATEGORY_OFFSET;
            goto alloc_sii;
        }
        fsm->sii_offset = next_offset;
        ec_fsm_sii_read(&fsm->fsm_sii, slave, fsm->sii_offset,
                        EC_FSM_SII_USE_CONFIGURED_ADDRESS);
        ec_fsm_sii_exec(&fsm->fsm_sii); // execute state immediately
        return;
    }

    word_count = fsm->sii_offset + 1;

alloc_sii:
    if (ec_sii_page_alloc(&slave->sii_page, word_count)) {
        EC_SLAVE_ERR(slave, "Failed to allocate %zu words of SII data.\n",
               word_count);
        slave->error_flag = 1;
        fsm->state = ec_fsm_slave_scan_state_error;
        return;
    }

    // Start fetching SII contents

    fsm->state = ec_fsm_slave_scan_state_sii_data;
    fsm->sii_offset = 0x0000;
    ec_fsm_sii_read(&fsm->fsm_sii, slave, fsm->sii_offset,
            EC_FSM_SII_USE_CONFIGURED_ADDRESS);
    ec_fsm_sii_exec(&fsm->fsm_sii); // execute state immediately
}

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

void ec_fsm_slave_scan_state_sii_data(
        ec_fsm_slave_scan_t *fsm 
        )
{
    ec_slave_t *slave = fsm->slave;
    unsigned int words_fitting;
    int words_to_copy;

    if (ec_fsm_sii_exec(&fsm->fsm_sii)) return;

    if (!ec_fsm_sii_success(&fsm->fsm_sii)) {
        fsm->slave->error_flag = 1;
        fsm->state = ec_fsm_slave_scan_state_error;
        EC_SLAVE_ERR(slave, "Failed to fetch SII contents.\n");
        return;
    }

    // Did we get 2 or 4 words?
    words_fitting = slave->sii_page.word_count - fsm->sii_offset;
    words_to_copy = min(words_fitting, fsm->fsm_sii.read_word_count);
    memcpy(slave->sii_page.words + fsm->sii_offset, fsm->fsm_sii.value,
            words_to_copy * 2);

    if (fsm->sii_offset + fsm->fsm_sii.read_word_count
            < slave->sii_page.word_count) {
        // fetch the next words
        fsm->sii_offset += fsm->fsm_sii.read_word_count;
        ec_fsm_sii_read(&fsm->fsm_sii, slave, fsm->sii_offset,
                        EC_FSM_SII_USE_CONFIGURED_ADDRESS);
        ec_fsm_sii_exec(&fsm->fsm_sii); // execute state immediately
        return;
    }

    slave->sii_page.origin = EC_SII_PAGE_FETCHED;

    // All words read. Evaluate the SII contents...
    if (ec_slave_analyze_sii_data(slave)) {
        EC_SLAVE_ERR(slave, "Failed to analyze category data.\n");
        fsm->slave->error_flag = 1;
        fsm->state = ec_fsm_slave_scan_state_error;
    }

    // Add the page that we just read to the cache
    ec_master_cache_sii_page(slave->master, &slave->sii_page);

#ifdef EC_REGALIAS
    ec_fsm_slave_scan_enter_regalias(fsm);
#else
    if (slave->sii.mailbox_protocols & EC_MBOX_COE) {
        ec_fsm_slave_scan_enter_preop(fsm);
    } else {
        fsm->state = ec_fsm_slave_scan_state_end;
    }
#endif
}

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

#ifdef EC_REGALIAS

void ec_fsm_slave_scan_enter_regalias(
        ec_fsm_slave_scan_t *fsm 
        )
{
    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_t *slave = fsm->slave;

    // read alias from register
    EC_SLAVE_DBG(slave, 1, "Reading alias from register.\n");
    ec_datagram_fprd(datagram, slave->station_address, 0x0012, 2);
    ec_datagram_zero(datagram);
    fsm->retries = EC_FSM_RETRIES;
    fsm->state = ec_fsm_slave_scan_state_regalias;
}

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

void ec_fsm_slave_scan_state_regalias(
        ec_fsm_slave_scan_t *fsm 
        )
{
    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_t *slave = fsm->slave;

    if (datagram->state == EC_DATAGRAM_TIMED_OUT && fsm->retries--)
        return;

    if (datagram->state != EC_DATAGRAM_RECEIVED) {
        fsm->state = ec_fsm_slave_scan_state_error;
        EC_SLAVE_ERR(slave, "Failed to receive register alias datagram: ");
        ec_datagram_print_state(datagram);
        return;
    }

    if (datagram->working_counter != 1) {
        EC_SLAVE_DBG(slave, 1, "Failed to read register alias.\n");
    } else {
        slave->effective_alias = EC_READ_U16(datagram->data);
        EC_SLAVE_DBG(slave, 1, "Read alias %u from register.\n",
                slave->effective_alias);
    }

    if (slave->sii.mailbox_protocols & EC_MBOX_COE) {
        ec_fsm_slave_scan_enter_preop(fsm);
    } else {
        fsm->state = ec_fsm_slave_scan_state_end;
    }
}

#endif // defined EC_REGALIAS

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

void ec_fsm_slave_scan_enter_preop(
        ec_fsm_slave_scan_t *fsm 
        )
{
    ec_slave_t *slave = fsm->slave;
    uint8_t current_state = slave->current_state & EC_SLAVE_STATE_MASK;

    if (current_state != EC_SLAVE_STATE_PREOP
            && current_state != EC_SLAVE_STATE_SAFEOP
            && current_state != EC_SLAVE_STATE_OP) {
        if (slave->master->debug_level) {
            char str[EC_STATE_STRING_SIZE];
            ec_state_string(current_state, str, 0);
            EC_SLAVE_DBG(slave, 0, "Slave is not in the state"
                    " to do mailbox com (%s), setting to PREOP.\n", str);
        }

        fsm->state = ec_fsm_slave_scan_state_preop;
        ec_slave_request_state(slave, EC_SLAVE_STATE_PREOP);
        ec_fsm_slave_config_start(fsm->fsm_slave_config, slave);
        ec_fsm_slave_config_exec(fsm->fsm_slave_config);
    } else {
        EC_SLAVE_DBG(slave, 1, "Reading mailbox"
                " sync manager configuration.\n");

        /* Scan current sync manager configuration to get configured mailbox
         * sizes. */
        ec_datagram_fprd(fsm->datagram, slave->station_address, 0x0800,
                EC_SYNC_PAGE_SIZE * 2);
        fsm->retries = EC_FSM_RETRIES;
        fsm->state = ec_fsm_slave_scan_state_sync;
    }
}

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

void ec_fsm_slave_scan_state_preop(
        ec_fsm_slave_scan_t *fsm 
        )
{
    if (ec_fsm_slave_config_exec(fsm->fsm_slave_config))
        return;

    if (!ec_fsm_slave_config_success(fsm->fsm_slave_config)) {
        fsm->state = ec_fsm_slave_scan_state_error;
        return;
    }

    ec_fsm_slave_scan_enter_clear_mailbox(fsm);
}

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

void ec_fsm_slave_scan_state_sync(
        ec_fsm_slave_scan_t *fsm 
        )
{
    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_t *slave = fsm->slave;
    uint16_t tx_offset, tx_size, rx_offset, rx_size;

    if (datagram->state == EC_DATAGRAM_TIMED_OUT && fsm->retries--)
        return;

    if (datagram->state != EC_DATAGRAM_RECEIVED) {
        fsm->state = ec_fsm_slave_scan_state_error;
        EC_SLAVE_ERR(slave, "Failed to receive sync manager"
                " configuration datagram: ");
        ec_datagram_print_state(datagram);
        return;
    }

    if (datagram->working_counter != 1) {
        fsm->slave->error_flag = 1;
        fsm->state = ec_fsm_slave_scan_state_error;
        EC_SLAVE_ERR(slave, "Failed to read DL status: ");
        ec_datagram_print_wc_error(datagram);
        return;
    }

    rx_offset = EC_READ_U16(datagram->data);
    rx_size = EC_READ_U16(datagram->data + 2);
    tx_offset = EC_READ_U16(datagram->data + 8);
    tx_size = EC_READ_U16(datagram->data + 10);

    if (rx_size == 0xffff) {
        fsm->state = ec_fsm_slave_scan_state_error;
        slave->sii.mailbox_protocols = 0x0000;
        EC_SLAVE_ERR(slave, "Invalid RX mailbox size (%u) configured."
                " Disabling mailbox communication.", rx_size);
        return;
    }

    if (tx_size == 0xffff) {
        fsm->state = ec_fsm_slave_scan_state_error;
        slave->sii.mailbox_protocols = 0x0000;
        EC_SLAVE_ERR(slave, "Invalid TX mailbox size (%u) configured."
                " Disabling mailbox communication.", tx_size);
        return;
    }

    slave->configured_rx_mailbox_offset = rx_offset;
    slave->configured_rx_mailbox_size = rx_size;
    slave->configured_tx_mailbox_offset = tx_offset;
    slave->configured_tx_mailbox_size = tx_size;

    EC_SLAVE_DBG(slave, 1, "Mailbox configuration:\n");
    EC_SLAVE_DBG(slave, 1, " RX offset=0x%04x size=%u\n",
            slave->configured_rx_mailbox_offset,
            slave->configured_rx_mailbox_size);
    EC_SLAVE_DBG(slave, 1, " TX offset=0x%04x size=%u\n",
            slave->configured_tx_mailbox_offset,
            slave->configured_tx_mailbox_size);

    // allocate memory for mailbox response data
    ec_slave_mbox_prealloc(slave);

    ec_fsm_slave_scan_enter_clear_mailbox(fsm);
}

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

void ec_fsm_slave_scan_enter_clear_mailbox(
        ec_fsm_slave_scan_t *fsm 
        )
{
    ec_slave_t *slave = fsm->slave;

    // If there is some old data in the slave's mailbox, read it out and
    // discard it. We don't need to check the mailbox first, we just ignore
    // an error or empty mailbox response.
    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_mbox_prepare_fetch(fsm->slave, datagram);
    fsm->retries = EC_FSM_RETRIES;
    fsm->state = ec_fsm_slave_scan_state_mailbox_cleared;

    slave->valid_mbox_data = 0;
}

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

void ec_fsm_slave_scan_state_mailbox_cleared(
        ec_fsm_slave_scan_t *fsm 
        )
{
    ec_slave_t *slave = fsm->slave;
    ec_datagram_t *datagram = fsm->datagram;

    if (fsm->datagram->state == EC_DATAGRAM_TIMED_OUT && fsm->retries--) {
        ec_slave_mbox_prepare_fetch(fsm->slave, datagram);
        return;
    }

    if (unlikely(slave->master->debug_level > 0)
        && datagram->state == EC_DATAGRAM_RECEIVED
        && datagram->working_counter == 1)
        EC_SLAVE_INFO(slave, "Cleared old data from the mailbox\n");

    slave->valid_mbox_data = 1;

    ec_fsm_slave_scan_enter_pdos(fsm);
}

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

void ec_fsm_slave_scan_enter_pdos(
        ec_fsm_slave_scan_t *fsm 
        )
{
    ec_slave_t *slave = fsm->slave;
    ec_pdo_mode_t assign_mode = EC_PDO_MODE_DEFAULT;
    ec_pdo_mode_t config_mode = EC_PDO_MODE_DEFAULT;
    const ec_slave_config_t *sc;

    // Look up a not-yet-attached configuration for this slave (attaching
    // only happens after the whole bus has been scanned) to find out if
    // the application requested non-default PDO scanning behavior.
    if ((sc = ec_master_find_config_for_slave(slave->master, slave))) {
        assign_mode = sc->pdo_assign_mode;
        config_mode = sc->pdo_config_mode;
    }

    if (assign_mode == EC_PDO_MODE_FIXED
            || assign_mode == EC_PDO_MODE_WRITE) {
        if (config_mode == EC_PDO_MODE_FIXED
                || config_mode == EC_PDO_MODE_WRITE) {
            EC_SLAVE_DBG(slave, 1, "Skipping PDO scanning"
                    " (fixed PDO assignment/configuration).\n");
            fsm->state = ec_fsm_slave_scan_state_end;
            return;
        }
    }

    EC_SLAVE_DBG(slave, 1, "Scanning PDO assignment and mapping.\n");
    fsm->state = ec_fsm_slave_scan_state_pdos;
    ec_fsm_pdo_start_reading(fsm->fsm_pdo, slave, assign_mode, config_mode);
    ec_fsm_pdo_exec(fsm->fsm_pdo, fsm->datagram); // execute immediately
}

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

void ec_fsm_slave_scan_state_pdos(
        ec_fsm_slave_scan_t *fsm 
        )
{
    if (ec_fsm_pdo_exec(fsm->fsm_pdo, fsm->datagram)) {
        return;
    }

    if (!ec_fsm_pdo_success(fsm->fsm_pdo)) {
        fsm->state = ec_fsm_slave_scan_state_error;
        return;
    }

    // reading PDO configuration finished
    fsm->state = ec_fsm_slave_scan_state_end;
}

/*****************************************************************************
 * Common state functions
 ****************************************************************************/

void ec_fsm_slave_scan_state_error(
        ec_fsm_slave_scan_t *fsm 
        )
{
}

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

void ec_fsm_slave_scan_state_end(
        ec_fsm_slave_scan_t *fsm 
        )
{
}

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