/******************************************************************************
 *
 *  $Id$
 *
 *  Copyright (C) 2008  Olav Zarges, imc Messsysteme GmbH
 *
 *  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
 *
 *  ---
 *
 *  The license mentioned above concerns the source code only. Using the
 *  EtherCAT technology and brand is only permitted in compliance with the
 *  industrial property and similar rights of Beckhoff Automation GmbH.
 *
 *****************************************************************************/

/**
   \file
   EtherCAT FoE state machines.
*/

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

#include "globals.h"
#include "master.h"
#include "mailbox.h"
#include "fsm_foe.h"
#include "foe.h"

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

/** Maximum time in ms to wait for responses when reading out the dictionary.
 */
#define EC_FSM_FOE_TIMEOUT 3000

/** Mailbox type FoE.
 */
#define EC_MBOX_TYPE_FILEACCESS 0x04

/** Size of the FoE header.
 */
#define EC_FOE_HEADER_SIZE 6
// uint8_t  OpCode
// uint8_t  reserved
// uint32_t PacketNo, Password, ErrorCode

//#define DEBUG_FOE

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

/** FoE OpCodes.
 */
enum {
    EC_FOE_OPCODE_RRQ  = 1, /**< Read request. */
    EC_FOE_OPCODE_WRQ  = 2, /**< Write request. */
    EC_FOE_OPCODE_DATA = 3, /**< Data. */
    EC_FOE_OPCODE_ACK  = 4, /**< Acknowledge. */
    EC_FOE_OPCODE_ERR  = 5, /**< Error. */
    EC_FOE_OPCODE_BUSY = 6  /**< Busy. */
} ec_foe_opcode_t;

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

int ec_foe_prepare_data_send(ec_fsm_foe_t *);
int ec_foe_prepare_wrq_send(ec_fsm_foe_t *);
int ec_foe_prepare_rrq_send(ec_fsm_foe_t *);
int ec_foe_prepare_send_ack(ec_fsm_foe_t *);

void ec_foe_set_tx_error(ec_fsm_foe_t *, uint32_t);
void ec_foe_set_rx_error(ec_fsm_foe_t *, uint32_t);

void ec_fsm_foe_write(ec_fsm_foe_t *);
void ec_fsm_foe_read(ec_fsm_foe_t *);
void ec_fsm_foe_end(ec_fsm_foe_t *);
void ec_fsm_foe_error(ec_fsm_foe_t *);

void ec_fsm_foe_state_wrq_sent(ec_fsm_foe_t *);
void ec_fsm_foe_state_rrq_sent(ec_fsm_foe_t *);

void ec_fsm_foe_state_ack_check(ec_fsm_foe_t *);
void ec_fsm_foe_state_ack_read(ec_fsm_foe_t *);

void ec_fsm_foe_state_data_sent(ec_fsm_foe_t *);

void ec_fsm_foe_state_data_check(ec_fsm_foe_t *);
void ec_fsm_foe_state_data_read(ec_fsm_foe_t *);
void ec_fsm_foe_state_sent_ack(ec_fsm_foe_t *);

void ec_fsm_foe_write_start(ec_fsm_foe_t *);
void ec_fsm_foe_read_start(ec_fsm_foe_t *);

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

/**
   Constructor.
*/

void ec_fsm_foe_init(ec_fsm_foe_t *fsm, /**< finite state machine */
                     ec_datagram_t *datagram /**< datagram */
                     )
{
    fsm->state     = NULL;
    fsm->datagram  = datagram;
    fsm->rx_errors = 0;
    fsm->tx_errors = 0;
}

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

/**
   Destructor.
*/

void ec_fsm_foe_clear(ec_fsm_foe_t *fsm /**< finite state machine */)
{
}

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

/**
   Executes the current state of the state machine.
   \return false, if state machine has terminated
*/

int ec_fsm_foe_exec(ec_fsm_foe_t *fsm /**< finite state machine */)
{
    fsm->state(fsm);

    return fsm->state != ec_fsm_foe_end && fsm->state != ec_fsm_foe_error;
}

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

/**
   Returns, if the state machine terminated with success.
   \return non-zero if successful.
*/

int ec_fsm_foe_success(ec_fsm_foe_t *fsm /**< Finite state machine */)
{
    return fsm->state == ec_fsm_foe_end;
}

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

/** Prepares an FoE transfer.
 */
void ec_fsm_foe_transfer(
        ec_fsm_foe_t *fsm, /**< State machine. */
        ec_slave_t *slave, /**< EtherCAT slave. */
        ec_foe_request_t *request /**< Sdo request. */
        )
{
    fsm->slave = slave;
    fsm->request = request;
    if (request->dir == EC_DIR_OUTPUT) {
        fsm->state = ec_fsm_foe_write;
    }
    else {
        fsm->state = ec_fsm_foe_read;
    }
}

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

/**
   State: ERROR.
*/

void ec_fsm_foe_error(ec_fsm_foe_t *fsm /**< finite state machine */)
{
#ifdef DEBUG_FOE
    printk("ec_fsm_foe_error()\n");
#endif
}

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

/**
   State: END.
*/

void ec_fsm_foe_end(ec_fsm_foe_t *fsm /**< finite state machine */)
{
#ifdef DEBUG_FOE
    printk("ec_fsm_foe_end\n");
#endif
}

/*****************************************************************************/
/**
   Sends a file or the next fragment.
*/

int ec_foe_prepare_data_send(ec_fsm_foe_t *fsm)
{
    size_t remaining_size, current_size;
    uint8_t *data;

    remaining_size = fsm->tx_buffer_size - fsm->tx_buffer_offset;

    if (remaining_size < fsm->slave->configured_tx_mailbox_size
            - EC_MBOX_HEADER_SIZE - EC_FOE_HEADER_SIZE) {
        current_size = remaining_size;
        fsm->tx_last_packet = 1;
    } else {
        current_size = fsm->slave->configured_tx_mailbox_size
            - EC_MBOX_HEADER_SIZE - EC_FOE_HEADER_SIZE;
    }

    data = ec_slave_mbox_prepare_send(fsm->slave,
            fsm->datagram, EC_MBOX_TYPE_FILEACCESS,
            current_size + EC_FOE_HEADER_SIZE);
    if (IS_ERR(data))
        return -1;

    EC_WRITE_U8 ( data, EC_FOE_OPCODE_DATA );    // OpCode = DataBlock req.
    EC_WRITE_U32( data + 2, fsm->tx_packet_no ); // PacketNo, Password

    memcpy(data + EC_FOE_HEADER_SIZE,
            fsm->tx_buffer + fsm->tx_buffer_offset, current_size);
    fsm->tx_current_size = current_size;

    return 0;
}

/*****************************************************************************/
/**
   Prepare a write request (WRQ) with filename
*/

int ec_foe_prepare_wrq_send(ec_fsm_foe_t *fsm)
{
    size_t current_size;
    uint8_t *data;

    fsm->tx_buffer_offset = 0;
    fsm->tx_current_size = 0;
    fsm->tx_packet_no = 0;
    fsm->tx_last_packet = 0;

    current_size = fsm->tx_filename_len;

    data = ec_slave_mbox_prepare_send(fsm->slave, fsm->datagram,
            EC_MBOX_TYPE_FILEACCESS, current_size + EC_FOE_HEADER_SIZE);
    if (IS_ERR(data))
        return -1;

    EC_WRITE_U16( data, EC_FOE_OPCODE_WRQ); // fsm write request
    EC_WRITE_U32( data + 2, fsm->tx_packet_no );

    memcpy(data + EC_FOE_HEADER_SIZE, fsm->tx_filename, current_size);

    return 0;
}

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

/** Start a write operation.
 */
void ec_fsm_foe_write(
        ec_fsm_foe_t *fsm /**< FoE statemachine. */
        )
{
    fsm->tx_buffer = fsm->request->buffer;
    fsm->tx_buffer_size = fsm->request->data_size;
    fsm->tx_buffer_offset = 0;

    fsm->tx_filename = fsm->request->file_name;
    fsm->tx_filename_len = strlen(fsm->tx_filename);

    fsm->state = ec_fsm_foe_write_start;
}

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

/** Initializes the FoE write state machine.
 */
void ec_fsm_foe_write_start(ec_fsm_foe_t *fsm /**< finite state machine */)
{
    ec_slave_t *slave = fsm->slave;

    fsm->tx_buffer_offset = 0;
    fsm->tx_current_size = 0;
    fsm->tx_packet_no = 0;
    fsm->tx_last_packet = 0;

#ifdef DEBUG_FOE
    printk("ec_fsm_foe_write_start()\n");
#endif

    if (!(slave->sii.mailbox_protocols & EC_MBOX_FOE)) {
        ec_foe_set_tx_error(fsm, FOE_MBOX_PROT_ERROR);
        EC_ERR("Slave %u does not support FoE!\n", slave->ring_position);
        return;
    }

    if (ec_foe_prepare_wrq_send(fsm)) {
        ec_foe_set_tx_error(fsm, FOE_PROT_ERROR);
        return;
    }

    fsm->state = ec_fsm_foe_state_wrq_sent;
}

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

/** Check for acknowledge.
 */
void ec_fsm_foe_state_ack_check(
        ec_fsm_foe_t *fsm /**< FoE statemachine. */
        )
{
    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_t *slave = fsm->slave;

#ifdef DEBUG_FOE
    printk("ec_fsm_foe_ack_check()\n");
#endif

    if (datagram->state != EC_DATAGRAM_RECEIVED) {
        ec_foe_set_rx_error(fsm, FOE_RECEIVE_ERROR);
        EC_ERR("Failed to receive FoE mailbox check datagram for slave %u: ",
               slave->ring_position);
        ec_datagram_print_state(datagram);
        return;
    }

    if (datagram->working_counter != 1) {
        // slave did not put anything in the mailbox yet
        ec_foe_set_rx_error(fsm, FOE_WC_ERROR);
        EC_ERR("Reception of FoE mailbox check datagram failed on slave %u: ",
               slave->ring_position);
        ec_datagram_print_wc_error(datagram);
        return;
    }

    if (!ec_slave_mbox_check(datagram)) {
        unsigned long diff_ms =
            (datagram->jiffies_received - fsm->jiffies_start) * 1000 / HZ;
        if (diff_ms >= EC_FSM_FOE_TIMEOUT) {
            ec_foe_set_tx_error(fsm, FOE_TIMEOUT_ERROR);
            EC_ERR("Timeout while waiting for ack response "
                    "on slave %u.\n", slave->ring_position);
            return;
        }

        ec_slave_mbox_prepare_check(slave, datagram); // can not fail.
        fsm->retries = EC_FSM_RETRIES;
        return;
    }

    // Fetch response
    ec_slave_mbox_prepare_fetch(slave, datagram); // can not fail.

    fsm->retries = EC_FSM_RETRIES;
    fsm->state = ec_fsm_foe_state_ack_read;
}

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

/** Acknowledge a read operation.
 */
void ec_fsm_foe_state_ack_read(
        ec_fsm_foe_t *fsm /**< FoE statemachine. */
        )
{
    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_t *slave = fsm->slave;
    uint8_t *data, mbox_prot;
    uint8_t opCode;
    size_t rec_size;

#ifdef DEBUG_FOE
    printk("ec_fsm_foe_ack_read()\n");
#endif

    if (datagram->state != EC_DATAGRAM_RECEIVED) {
        ec_foe_set_rx_error(fsm, FOE_RECEIVE_ERROR);
        EC_ERR("Failed to receive FoE ack response datagram for"
               " slave %u: ", slave->ring_position);
        ec_datagram_print_state(datagram);
        return;
    }

    if (datagram->working_counter != 1) {
        ec_foe_set_rx_error(fsm, FOE_WC_ERROR);
        EC_ERR("Reception of FoE ack response failed on slave %u: ",
                slave->ring_position);
        ec_datagram_print_wc_error(datagram);
        return;
    }

    if (!(data = ec_slave_mbox_fetch(fsm->slave, datagram,
                    &mbox_prot, &rec_size))) {
        ec_foe_set_tx_error(fsm, FOE_PROT_ERROR);
        return;
    }

    if (mbox_prot != EC_MBOX_TYPE_FILEACCESS) { // FoE
        ec_foe_set_tx_error(fsm, FOE_MBOX_PROT_ERROR);
        EC_ERR("Received mailbox protocol 0x%02X as response.\n", mbox_prot);
        return;
    }

    opCode = EC_READ_U8(data);

    if (opCode == EC_FOE_OPCODE_BUSY) {
        // slave not ready
        if (ec_foe_prepare_data_send(fsm)) {
            ec_foe_set_tx_error(fsm, FOE_PROT_ERROR);
            EC_ERR("Slave is busy.\n");
            return;
        }
        fsm->state = ec_fsm_foe_state_data_sent;
        return;
    }

    if (opCode == EC_FOE_OPCODE_ACK) {
        fsm->tx_packet_no++;
        fsm->tx_buffer_offset += fsm->tx_current_size;

        if (fsm->tx_last_packet) {
            fsm->state = ec_fsm_foe_end;
            return;
        }

        if (ec_foe_prepare_data_send(fsm)) {
            ec_foe_set_tx_error(fsm, FOE_PROT_ERROR);
            return;
        }
        fsm->state = ec_fsm_foe_state_data_sent;
        return;
    }
    ec_foe_set_tx_error(fsm, FOE_ACK_ERROR);
}

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

/** State: WRQ SENT.
 *
 * Checks is the previous transmit datagram succeded and sends the next
 * fragment, if necessary.
 */
void ec_fsm_foe_state_wrq_sent(
        ec_fsm_foe_t *fsm /**< FoE statemachine. */
        )
{
    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_t *slave = fsm->slave;

#ifdef DEBUG_FOE
    printk("ec_foe_state_sent_wrq()\n");
#endif

    if (datagram->state != EC_DATAGRAM_RECEIVED) {
        ec_foe_set_rx_error(fsm, FOE_RECEIVE_ERROR);
        EC_ERR("Failed to send FoE WRQ for slave %u: ",
                slave->ring_position);
        ec_datagram_print_state(datagram);
        return;
    }

    if (datagram->working_counter != 1) {
        // slave did not put anything in the mailbox yet
        ec_foe_set_rx_error(fsm, FOE_WC_ERROR);
        EC_ERR("Reception of FoE WRQ failed on slave %u: ",
                slave->ring_position);
        ec_datagram_print_wc_error(datagram);
        return;
    }

    fsm->jiffies_start = datagram->jiffies_sent;

    ec_slave_mbox_prepare_check(fsm->slave, datagram); // can not fail.

    fsm->retries = EC_FSM_RETRIES;
    fsm->state = ec_fsm_foe_state_ack_check;
}

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

/** State: WRQ SENT.
 *
 * Checks is the previous transmit datagram succeded and sends the next
 * fragment, if necessary.
 */
void ec_fsm_foe_state_data_sent(
        ec_fsm_foe_t *fsm /**< Foe statemachine. */
        )
{
    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_t *slave = fsm->slave;

#ifdef DEBUG_FOE
    printk("ec_fsm_foe_state_data_sent()\n");
#endif

    if (fsm->datagram->state != EC_DATAGRAM_RECEIVED) {
        ec_foe_set_tx_error(fsm, FOE_RECEIVE_ERROR);
        EC_ERR("Failed to receive FoE ack response datagram for"
               " slave %u: ", slave->ring_position);
        ec_datagram_print_state(datagram);
        return;
    }

    if (fsm->datagram->working_counter != 1) {
        ec_foe_set_tx_error(fsm, FOE_WC_ERROR);
        EC_ERR("Reception of FoE data send failed on slave %u: ",
                slave->ring_position);
        ec_datagram_print_wc_error(datagram);
        return;
    }

    ec_slave_mbox_prepare_check(fsm->slave, fsm->datagram);
    fsm->jiffies_start = jiffies;
    fsm->retries = EC_FSM_RETRIES;
    fsm->state = ec_fsm_foe_state_ack_check;
}

/*****************************************************************************/
/**
   Prepare a read request (RRQ) with filename
*/

int ec_foe_prepare_rrq_send(ec_fsm_foe_t *fsm)
{
    size_t current_size;
    uint8_t *data;

    current_size = fsm->rx_filename_len;

    data = ec_slave_mbox_prepare_send(fsm->slave, fsm->datagram,
            EC_MBOX_TYPE_FILEACCESS, current_size + EC_FOE_HEADER_SIZE);
    if (IS_ERR(data))
        return -1;

    EC_WRITE_U16(data, EC_FOE_OPCODE_RRQ); // fsm read request
    EC_WRITE_U32(data + 2, 0x00000000); // no passwd
    memcpy(data + EC_FOE_HEADER_SIZE, fsm->rx_filename, current_size);

    if (fsm->slave->master->debug_level) {
        EC_DBG("FoE Read Request:\n");
        ec_print_data(data, current_size + EC_FOE_HEADER_SIZE);
    }

    return 0;
}


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

/** Prepare to send an acknowledge.
 */
int ec_foe_prepare_send_ack(
        ec_fsm_foe_t *foe /**< FoE statemachine. */
        )
{
    uint8_t *data;

    data = ec_slave_mbox_prepare_send(foe->slave, foe->datagram,
            EC_MBOX_TYPE_FILEACCESS, EC_FOE_HEADER_SIZE);
    if (IS_ERR(data))
        return -1;

    EC_WRITE_U16(data, EC_FOE_OPCODE_ACK);
    EC_WRITE_U32(data + 2, foe->rx_expected_packet_no);

    return 0;
}

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

/** State: RRQ SENT.
 *
 * Checks is the previous transmit datagram succeded and sends the next
 * fragment, if necessary.
 */
void ec_fsm_foe_state_rrq_sent(
        ec_fsm_foe_t *fsm /**< FoE statemachine. */
        )
{
    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_t *slave = fsm->slave;

#ifdef DEBUG_FOE
    printk("ec_foe_state_rrq_sent()\n");
#endif

    if (datagram->state != EC_DATAGRAM_RECEIVED) {
        ec_foe_set_rx_error(fsm, FOE_RECEIVE_ERROR);
        EC_ERR("Failed to send FoE RRQ for slave %u" ": ",
                slave->ring_position);
        ec_datagram_print_state(datagram);
        return;
    }

    if (datagram->working_counter != 1) {
        // slave did not put anything in the mailbox yet
        ec_foe_set_rx_error(fsm, FOE_WC_ERROR);
        EC_ERR("Reception of FoE RRQ failed on slave %u: ",
                slave->ring_position);
        ec_datagram_print_wc_error(datagram);
        return;
    }

    fsm->jiffies_start = datagram->jiffies_sent;

    ec_slave_mbox_prepare_check(fsm->slave, datagram); // can not fail.

    fsm->retries = EC_FSM_RETRIES;
    fsm->state = ec_fsm_foe_state_data_check;
}

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

/** Start a read operation.
 */
void ec_fsm_foe_read(
        ec_fsm_foe_t *fsm /**< FoE state machine. */
        )
{
    fsm->state = ec_fsm_foe_read_start;
    fsm->rx_filename = fsm->request->file_name;
    fsm->rx_filename_len = strlen(fsm->rx_filename);

    fsm->rx_buffer = fsm->request->buffer;
    fsm->rx_buffer_size = fsm->request->buffer_size;
}

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

/** Starting state for read operations.
 */
void ec_fsm_foe_read_start(
        ec_fsm_foe_t *fsm /**< FoE statemachine. */
        )
{
    size_t current_size;
    ec_slave_t *slave = fsm->slave;

    fsm->rx_buffer_offset = 0;
    fsm->rx_current_size = 0;
    fsm->rx_packet_no = 0;
    fsm->rx_expected_packet_no = 1;
    fsm->rx_last_packet = 0;

    current_size = fsm->rx_filename_len;

#ifdef DEBUG_FOE
    printk("ec_fsm_foe_read_start()\n");
#endif

    if (!(slave->sii.mailbox_protocols & EC_MBOX_FOE)) {
        ec_foe_set_tx_error(fsm, FOE_MBOX_PROT_ERROR);
        EC_ERR("Slave %u does not support FoE!\n", slave->ring_position);
        return;
    }

    if (ec_foe_prepare_rrq_send(fsm)) {
        ec_foe_set_rx_error(fsm, FOE_PROT_ERROR);
        return;
    }

    fsm->state = ec_fsm_foe_state_rrq_sent;
}

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

/** Check for data.
 */
void ec_fsm_foe_state_data_check(
        ec_fsm_foe_t *fsm /**< FoE statemachine. */
        )
{
    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_t *slave = fsm->slave;

#ifdef DEBUG_FOE
    printk("ec_fsm_foe_state_data_check()\n");
#endif

    if (datagram->state != EC_DATAGRAM_RECEIVED) {
        ec_foe_set_rx_error(fsm, FOE_RECEIVE_ERROR);
        EC_ERR("Failed to send FoE DATA READ for slave %u: ",
                slave->ring_position);
        ec_datagram_print_state(datagram);
        return;
    }

    if (datagram->working_counter != 1) {
        ec_foe_set_rx_error(fsm, FOE_WC_ERROR);
        EC_ERR("Reception of FoE DATA READ on slave %u: ",
                slave->ring_position);
        ec_datagram_print_wc_error(datagram);
        return;
    }

    if (!ec_slave_mbox_check(datagram)) {
        unsigned long diff_ms =
            (datagram->jiffies_received - fsm->jiffies_start) * 1000 / HZ;
        if (diff_ms >= EC_FSM_FOE_TIMEOUT) {
            ec_foe_set_tx_error(fsm, FOE_TIMEOUT_ERROR);
            EC_ERR("Timeout while waiting for ack response "
                    "on slave %u.\n", slave->ring_position);
            return;
        }

        ec_slave_mbox_prepare_check(slave, datagram); // can not fail.
        fsm->retries = EC_FSM_RETRIES;
        return;
    }

    // Fetch response
    ec_slave_mbox_prepare_fetch(slave, datagram); // can not fail.

    fsm->retries = EC_FSM_RETRIES;
    fsm->state = ec_fsm_foe_state_data_read;

}

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

/** Start reading data.
 */
void ec_fsm_foe_state_data_read(
        ec_fsm_foe_t *fsm /**< FoE statemachine. */
        )
{
    size_t rec_size;
    uint8_t *data, opCode, packet_no, mbox_prot;

    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_t *slave = fsm->slave;

#ifdef DEBUG_FOE
    printk("ec_fsm_foe_state_data_read()\n");
#endif

    if (datagram->state != EC_DATAGRAM_RECEIVED) {
        ec_foe_set_rx_error(fsm, FOE_RECEIVE_ERROR);
        EC_ERR("Failed to receive FoE DATA READ datagram for"
               " slave %u: ", slave->ring_position);
        ec_datagram_print_state(datagram);
        return;
    }

    if (datagram->working_counter != 1) {
        ec_foe_set_rx_error(fsm, FOE_WC_ERROR);
        EC_ERR("Reception of FoE DATA READ failed on slave %u: ",
                slave->ring_position);
        ec_datagram_print_wc_error(datagram);
        return;
    }

    if (!(data = ec_slave_mbox_fetch(slave, datagram, &mbox_prot, &rec_size))) {
        ec_foe_set_rx_error(fsm, FOE_MBOX_FETCH_ERROR);
        return;
    }

    if (mbox_prot != EC_MBOX_TYPE_FILEACCESS) { // FoE
        EC_ERR("Received mailbox protocol 0x%02X as response.\n", mbox_prot);
        ec_foe_set_rx_error(fsm, FOE_PROT_ERROR);
        return;
    }

    opCode = EC_READ_U8(data);

    if (opCode == EC_FOE_OPCODE_BUSY) {
        if (ec_foe_prepare_send_ack(fsm)) {
            ec_foe_set_rx_error(fsm, FOE_PROT_ERROR);
        }
        return;
    }

    if (opCode == EC_FOE_OPCODE_ERR) {
        fsm->request->error_code = EC_READ_U32(data + 2);
        EC_ERR("Received FoE Error Request (code 0x%08x) on slave %u.\n",
                fsm->request->error_code, slave->ring_position);
        if (rec_size > 6) {
            uint8_t text[1024];
            strncpy(text, data + 6, min(rec_size - 6, sizeof(text)));
            EC_ERR("FoE Error Text: %s\n", text);
        }
        ec_foe_set_rx_error(fsm, FOE_OPCODE_ERROR);
        return;
    }

    if (opCode != EC_FOE_OPCODE_DATA) {
        EC_ERR("Received OPCODE %x, expected %x on slave %u.\n",
                opCode, EC_FOE_OPCODE_DATA, slave->ring_position);
        fsm->request->error_code = 0x00000000;
        ec_foe_set_rx_error(fsm, FOE_OPCODE_ERROR);
        return;
    }

    packet_no = EC_READ_U16(data + 2);
    if (packet_no != fsm->rx_expected_packet_no) {
        EC_ERR("Received unexpected packet number on slave %u.\n",
                slave->ring_position);
        ec_foe_set_rx_error(fsm, FOE_PACKETNO_ERROR);
        return;
    }

    rec_size -= EC_FOE_HEADER_SIZE;

    if (fsm->rx_buffer_size >= fsm->rx_buffer_offset + rec_size) {
        memcpy(fsm->rx_buffer + fsm->rx_buffer_offset,
                data + EC_FOE_HEADER_SIZE, rec_size);
        fsm->rx_buffer_offset += rec_size;
    }

    fsm->rx_last_packet =
        (rec_size + EC_MBOX_HEADER_SIZE + EC_FOE_HEADER_SIZE
         != fsm->slave->configured_rx_mailbox_size);

    if (fsm->rx_last_packet ||
            (slave->configured_rx_mailbox_size - EC_MBOX_HEADER_SIZE
             - EC_FOE_HEADER_SIZE + fsm->rx_buffer_offset)
            <= fsm->rx_buffer_size) {
        // either it was the last packet or a new packet will fit into the
        // delivered buffer
#ifdef DEBUG_FOE
        printk ("last_packet=true\n");
#endif
        if (ec_foe_prepare_send_ack(fsm)) {
            ec_foe_set_rx_error(fsm, FOE_RX_DATA_ACK_ERROR);
            return;
        }

        fsm->state = ec_fsm_foe_state_sent_ack;
    }
    else {
        // no more data fits into the delivered buffer
        // ... wait for new read request
        printk ("ERROR: data doesn't fit in receive buffer\n");
        printk ("       rx_buffer_size  = %d\n", fsm->rx_buffer_size);
        printk ("       rx_buffer_offset= %d\n", fsm->rx_buffer_offset);
        printk ("       rec_size        = %zd\n", rec_size);
        printk ("       rx_mailbox_size = %d\n",
                slave->configured_rx_mailbox_size);
        printk ("       rx_last_packet  = %d\n", fsm->rx_last_packet);
        fsm->request->result = FOE_READY;
    }
}

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

/** Sent an acknowledge.
 */
void ec_fsm_foe_state_sent_ack(
        ec_fsm_foe_t *fsm /**< FoE statemachine. */
        )
{
    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_t *slave = fsm->slave;

#ifdef DEBUG_FOE
    printk("ec_foe_state_sent_ack()\n");
#endif

    if (datagram->state != EC_DATAGRAM_RECEIVED) {
        ec_foe_set_rx_error(fsm, FOE_RECEIVE_ERROR);
        EC_ERR("Failed to send FoE ACK for slave %u: ",
                slave->ring_position);
        ec_datagram_print_state(datagram);
        return;
    }

    if (datagram->working_counter != 1) {
        // slave did not put anything into the mailbox yet
        ec_foe_set_rx_error(fsm, FOE_WC_ERROR);
        EC_ERR("Reception of FoE ACK failed on slave %u: ",
                slave->ring_position);
        ec_datagram_print_wc_error(datagram);
        return;
    }

    fsm->jiffies_start = datagram->jiffies_sent;

    ec_slave_mbox_prepare_check(fsm->slave, datagram); // can not fail.

    if (fsm->rx_last_packet) {
        fsm->rx_expected_packet_no = 0;
        fsm->request->data_size = fsm->rx_buffer_offset;
        fsm->state = ec_fsm_foe_end;
    }
    else {
        fsm->rx_expected_packet_no++;
        fsm->retries = EC_FSM_RETRIES;
        fsm->state = ec_fsm_foe_state_data_check;
    }
}

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

/** Set an error code and go to the send error state.
 */
void ec_foe_set_tx_error(
        ec_fsm_foe_t *fsm, /**< FoE statemachine. */
        uint32_t errorcode /**< FoE error code. */
        )
{
    fsm->tx_errors++;
    fsm->request->result = errorcode;
    fsm->state = ec_fsm_foe_error;
}

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

/** Set an error code and go to the receive error state.
 */
void ec_foe_set_rx_error(
        ec_fsm_foe_t *fsm, /**< FoE statemachine. */
        uint32_t errorcode /**< FoE error code. */
        )
{
    fsm->rx_errors++;
    fsm->request->result = errorcode;
    fsm->state = ec_fsm_foe_error;
}

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