Slave configuration exclusively from master thread; removed
authorFlorian Pose <fp@igh-essen.com>
Mon, 12 Mar 2007 18:21:42 +0000
changeset 656 370aa8c2d1b1
parent 655 3702f0d6693b
child 657 7756b9f2eac2
Slave configuration exclusively from master thread; removed
ec_master_sync_io(); introduced events in the master state machine;
locking of slave scanning and slave configuration through allow_scan
and allow_config flags.
NEWS
TODO
master/fsm_master.c
master/fsm_master.h
master/master.c
master/master.h
master/slave.c
--- a/NEWS	Mon Mar 12 18:15:06 2007 +0000
+++ b/NEWS	Mon Mar 12 18:21:42 2007 +0000
@@ -37,6 +37,9 @@
 * Implemented setting of secondary slave address (alias) via sysfs.
 * Implemented SDO reading in operation mode via sysfs.
 * Removed annoying eeprom_write_enable file. EEPROM writing always enabled.
+* Slave configuration is now done exclusively from the master thread. Removed
+  ec_master_sync_io(). Userspace threads are now waiting for events in the
+  state machine.
 * Master state machine scheduled with timeout if idle, otherwise is executed
   as fast as possible (with schedule()).
 * Removed EtherCAT line comments from 8139too drivers.
--- a/TODO	Mon Mar 12 18:15:06 2007 +0000
+++ b/TODO	Mon Mar 12 18:21:42 2007 +0000
@@ -28,6 +28,10 @@
   - SDO write access in sysfs.
   - Configure slave ports to automatically open on link detection.
   - Calculate cycle time of operation state machine.
+  - Locking for serveral slave variables for sysfs access.
+  - Interrupt master state machines state scan for other jobs.
+  - Master state machine, slave configuration: Do not check every slave on
+    a cycle.
 
 * Less important issues:
   - Implement all EtherCAT datagram types.
--- a/master/fsm_master.c	Mon Mar 12 18:15:06 2007 +0000
+++ b/master/fsm_master.c	Mon Mar 12 18:21:42 2007 +0000
@@ -221,53 +221,68 @@
         EC_INFO("Slave states: %s.\n", states);
     }
 
-    // topology change in idle mode: clear all slaves and scan the bus
-    if (fsm->topology_change_pending &&
-            master->mode == EC_MASTER_MODE_IDLE) {
-        fsm->topology_change_pending = 0;
-        fsm->tainted = 0;
-        fsm->idle = 0;
-        fsm->scan_jiffies = jiffies;
-
-        ec_master_eoe_stop(master);
-        ec_master_destroy_slaves(master);
-
-        master->slave_count = datagram->working_counter;
-
-        if (!master->slave_count) {
-            // no slaves present -> finish state machine.
-            fsm->state = ec_fsm_master_state_end;
-            return;
-        }
-
-        // init slaves
-        for (i = 0; i < master->slave_count; i++) {
-            if (!(slave = (ec_slave_t *) kmalloc(sizeof(ec_slave_t),
-                                                 GFP_ATOMIC))) {
-                EC_ERR("Failed to allocate slave %i!\n", i);
-                ec_master_destroy_slaves(master);
-                fsm->state = ec_fsm_master_state_error;
+    if (fsm->topology_change_pending) {
+        down(&master->scan_sem);
+        if (!master->allow_scan) {
+            up(&master->scan_sem);
+        }
+        else {
+            master->scan_state = EC_REQUEST_IN_PROGRESS;
+            up(&master->scan_sem);
+            
+            // topology change when scan is allowed:
+            // clear all slaves and scan the bus
+            fsm->topology_change_pending = 0;
+            fsm->tainted = 0;
+            fsm->idle = 0;
+            fsm->scan_jiffies = jiffies;
+
+            ec_master_eoe_stop(master);
+            ec_master_destroy_slaves(master);
+
+            master->slave_count = datagram->working_counter;
+
+            if (!master->slave_count) {
+                // no slaves present -> finish state machine.
+                master->scan_state = EC_REQUEST_COMPLETE;
+                wake_up_interruptible(&master->scan_queue);
+                fsm->state = ec_fsm_master_state_end;
                 return;
             }
 
-            if (ec_slave_init(slave, master, i, i + 1)) {
-                // freeing of "slave" already done
-                ec_master_destroy_slaves(master);
-                fsm->state = ec_fsm_master_state_error;
-                return;
+            // init slaves
+            for (i = 0; i < master->slave_count; i++) {
+                if (!(slave = (ec_slave_t *) kmalloc(sizeof(ec_slave_t),
+                                GFP_ATOMIC))) {
+                    EC_ERR("Failed to allocate slave %i!\n", i);
+                    ec_master_destroy_slaves(master);
+                    master->scan_state = EC_REQUEST_FAILURE;
+                    wake_up_interruptible(&master->scan_queue);
+                    fsm->state = ec_fsm_master_state_error;
+                    return;
+                }
+
+                if (ec_slave_init(slave, master, i, i + 1)) {
+                    // freeing of "slave" already done
+                    ec_master_destroy_slaves(master);
+                    master->scan_state = EC_REQUEST_FAILURE;
+                    wake_up_interruptible(&master->scan_queue);
+                    fsm->state = ec_fsm_master_state_error;
+                    return;
+                }
+
+                list_add_tail(&slave->list, &master->slaves);
             }
 
-            list_add_tail(&slave->list, &master->slaves);
-        }
-
-        EC_INFO("Scanning bus.\n");
-
-        // begin scanning of slaves
-        fsm->slave = list_entry(master->slaves.next, ec_slave_t, list);
-        fsm->state = ec_fsm_master_state_scan_slaves;
-        ec_fsm_slave_start_scan(&fsm->fsm_slave, fsm->slave);
-        ec_fsm_slave_exec(&fsm->fsm_slave); // execute immediately
-        return;
+            EC_INFO("Scanning bus.\n");
+
+            // begin scanning of slaves
+            fsm->slave = list_entry(master->slaves.next, ec_slave_t, list);
+            fsm->state = ec_fsm_master_state_scan_slaves;
+            ec_fsm_slave_start_scan(&fsm->fsm_slave, fsm->slave);
+            ec_fsm_slave_exec(&fsm->fsm_slave); // execute immediately
+            return;
+        }
     }
 
     // fetch state from each slave
@@ -392,36 +407,35 @@
 /*****************************************************************************/
 
 /**
-   Master action: PROC_STATES.
-   Processes the slave states.
-*/
-
-void ec_fsm_master_action_process_states(ec_fsm_master_t *fsm
-                                         /**< master state machine */
-                                         )
-{
+ */
+
+int ec_fsm_master_action_configure(
+        ec_fsm_master_t *fsm /**< master state machine */
+        )
+{
+    ec_slave_t *slave;
     ec_master_t *master = fsm->master;
-    ec_slave_t *slave;
     char old_state[EC_STATE_STRING_SIZE], new_state[EC_STATE_STRING_SIZE];
 
     // check if any slaves are not in the state, they're supposed to be
+    // FIXME do not check all slaves in every cycle...
     list_for_each_entry(slave, &master->slaves, list) {
         if (slave->error_flag
-            || slave->online_state == EC_SLAVE_OFFLINE
-            || slave->requested_state == EC_SLAVE_STATE_UNKNOWN
-            || (slave->current_state == slave->requested_state
-                && slave->self_configured)) continue;
+                || slave->online_state == EC_SLAVE_OFFLINE
+                || slave->requested_state == EC_SLAVE_STATE_UNKNOWN
+                || (slave->current_state == slave->requested_state
+                    && slave->self_configured)) continue;
 
         if (master->debug_level) {
             ec_state_string(slave->current_state, old_state);
             if (slave->current_state != slave->requested_state) {
                 ec_state_string(slave->requested_state, new_state);
                 EC_DBG("Changing state of slave %i (%s -> %s).\n",
-                       slave->ring_position, old_state, new_state);
+                        slave->ring_position, old_state, new_state);
             }
             else if (!slave->self_configured) {
                 EC_DBG("Reconfiguring slave %i (%s).\n",
-                       slave->ring_position, old_state);
+                        slave->ring_position, old_state);
             }
         }
 
@@ -430,7 +444,43 @@
         fsm->state = ec_fsm_master_state_configure_slave;
         ec_fsm_slave_start_conf(&fsm->fsm_slave, slave);
         ec_fsm_slave_exec(&fsm->fsm_slave); // execute immediately
-        return;
+        return 1;
+    }
+
+    if (fsm->config_error)
+        master->config_state = EC_REQUEST_FAILURE;
+    else
+        master->config_state = EC_REQUEST_COMPLETE;
+    wake_up_interruptible(&master->config_queue);
+    return 0;
+}
+
+/*****************************************************************************/
+
+/**
+   Master action: PROC_STATES.
+   Processes the slave states.
+*/
+
+void ec_fsm_master_action_process_states(ec_fsm_master_t *fsm
+                                         /**< master state machine */
+                                         )
+{
+    ec_master_t *master = fsm->master;
+    ec_slave_t *slave;
+
+    down(&master->config_sem);
+    if (!master->allow_config) {
+        up(&master->config_sem);
+    }
+    else {
+        master->config_state = EC_REQUEST_IN_PROGRESS;
+        fsm->config_error = 0;
+        up(&master->config_sem);
+        
+        // check for pending slave configurations
+        if (ec_fsm_master_action_configure(fsm))
+            return;
     }
 
     // Check, if EoE processing has to be started
@@ -769,13 +819,8 @@
 
     EC_INFO("Bus scanning completed in %u ms.\n",
             (u32) (jiffies - fsm->scan_jiffies) * 1000 / HZ);
-
-    // set initial states of all slaves to PREOP to make mailbox
-    // communication possible
-    list_for_each_entry(slave, &master->slaves, list) {
-        if (slave->requested_state == EC_SLAVE_STATE_UNKNOWN)
-            ec_slave_request_state(slave, EC_SLAVE_STATE_PREOP);
-    }
+    master->scan_state = EC_REQUEST_COMPLETE;
+    wake_up_interruptible(&master->scan_queue);
 
     fsm->state = ec_fsm_master_state_end;
 }
@@ -794,7 +839,14 @@
     if (ec_fsm_slave_exec(&fsm->fsm_slave)) // execute slave's state machine
         return;
 
-    ec_fsm_master_action_process_states(fsm);
+    if (!ec_fsm_slave_success(&fsm->fsm_slave))
+        fsm->config_error = 1;
+
+    // configure next slave, if necessary
+    if (ec_fsm_master_action_configure(fsm))
+        return;
+
+    fsm->state = ec_fsm_master_state_end;
 }
 
 /*****************************************************************************/
--- a/master/fsm_master.h	Mon Mar 12 18:15:06 2007 +0000
+++ b/master/fsm_master.h	Mon Mar 12 18:21:42 2007 +0000
@@ -89,6 +89,7 @@
     unsigned int validate; /**< non-zero, if validation to do */
     unsigned int tainted; /**< non-zero, if the current bus topology does
                             not meet the initial conditions */
+    unsigned int config_error; /**< error during slave configuration */
     ec_slave_t *slave; /**< current slave */
     ec_eeprom_write_request_t *eeprom_request; /**< EEPROM write request */
     off_t eeprom_index; /**< index to EEPROM write request data */
--- a/master/master.c	Mon Mar 12 18:15:06 2007 +0000
+++ b/master/master.c	Mon Mar 12 18:21:42 2007 +0000
@@ -121,7 +121,17 @@
 
     INIT_LIST_HEAD(&master->slaves);
     master->slave_count = 0;
-
+    
+    master->scan_state = EC_REQUEST_IN_PROGRESS;
+    master->allow_scan = 1;
+    init_MUTEX(&master->scan_sem);
+    init_waitqueue_head(&master->scan_queue);
+
+    master->config_state = EC_REQUEST_COMPLETE;
+    master->allow_config = 1;
+    init_MUTEX(&master->config_sem);
+    init_waitqueue_head(&master->config_queue);
+    
     INIT_LIST_HEAD(&master->datagram_queue);
     master->datagram_index = 0;
 
@@ -320,24 +330,13 @@
 
 /**
  * Starts the master thread.
-*/
-
-int ec_master_thread_start(ec_master_t *master /**< EtherCAT master */)
-{
-    int (*thread_func)(ec_master_t *);
-
-    switch (master->mode) {
-        case EC_MASTER_MODE_IDLE:
-            thread_func = ec_master_idle_thread;
-            break;
-        case EC_MASTER_MODE_OPERATION:
-            thread_func = ec_master_operation_thread;
-            break;
-        default:
-            EC_ERR("Invalid master mode while starting thread!\n");
-            return -1;
-    }
-
+ */
+
+int ec_master_thread_start(
+        ec_master_t *master, /**< EtherCAT master */
+        int (*thread_func)(ec_master_t *) /**< thread function to start */
+        )
+{
     init_completion(&master->thread_exit);
 
     EC_INFO("Starting master thread.\n");
@@ -352,22 +351,32 @@
 
 /**
  * Stops the master thread.
-*/
+ */
 
 void ec_master_thread_stop(ec_master_t *master /**< EtherCAT master */)
 {
-    if (master->thread_id) {
-        kill_proc(master->thread_id, SIGTERM, 1);
-        wait_for_completion(&master->thread_exit);
-        EC_INFO("Master thread exited.\n");
-    }    
+    if (!master->thread_id) {
+        EC_WARN("ec_master_thread_stop: Already finished!\n");
+        return;
+    }
+
+    kill_proc(master->thread_id, SIGTERM, 1);
+    wait_for_completion(&master->thread_exit);
+    EC_INFO("Master thread exited.\n");
+
+    if (master->fsm_datagram.state != EC_DATAGRAM_SENT) return;
+    
+    // wait for FSM datagram
+    while (get_cycles() - master->fsm_datagram.cycles_sent
+            < (cycles_t) EC_IO_TIMEOUT /* us */ * (cpu_khz / 1000))
+        schedule();
 }
 
 /*****************************************************************************/
 
 /**
  * Transition function from ORPHANED to IDLE mode.
-*/
+ */
 
 int ec_master_enter_idle_mode(ec_master_t *master /**< EtherCAT master */)
 {
@@ -376,7 +385,7 @@
     master->cb_data = master;
 
     master->mode = EC_MASTER_MODE_IDLE;
-    if (ec_master_thread_start(master)) {
+    if (ec_master_thread_start(master, ec_master_idle_thread)) {
         master->mode = EC_MASTER_MODE_ORPHANED;
         return -1;
     }
@@ -388,7 +397,7 @@
 
 /**
  * Transition function from IDLE to ORPHANED mode.
-*/
+ */
 
 void ec_master_leave_idle_mode(ec_master_t *master /**< EtherCAT master */)
 {
@@ -403,57 +412,55 @@
 
 /**
  * Transition function from IDLE to OPERATION mode.
-*/
+ */
 
 int ec_master_enter_operation_mode(ec_master_t *master /**< EtherCAT master */)
 {
     ec_slave_t *slave;
 
-    ec_master_eoe_stop(master); // stop EoE timer
-    master->eoe_checked = 1; // prevent from starting again by FSM
-    ec_master_thread_stop(master);
-
-    master->mode = EC_MASTER_MODE_OPERATION;
-
-    // wait for FSM datagram
-    if (master->fsm_datagram.state == EC_DATAGRAM_SENT) {
-        while (get_cycles() - master->fsm_datagram.cycles_sent
-               < (cycles_t) EC_IO_TIMEOUT /* us */ * (cpu_khz / 1000)) {}
-        ecrt_master_receive(master);
-    }
-
-    // finish running IDLE FSM
-    if (ec_fsm_master_running(&master->fsm)) {
-        while (ec_fsm_master_exec(&master->fsm)) {
-            ec_master_queue_datagram(master, &master->fsm_datagram);
-            ec_master_sync_io(master);
-        }
-    }
-
-    if (master->debug_level) {
-        if (ec_master_measure_bus_time(master)) {
-            EC_ERR("Bus time measuring failed!\n");
-            goto out_idle;
-        }
-    }
-
-    // set initial slave states
+    down(&master->config_sem);
+    master->allow_config = 0; // temporarily disable slave configuration
+    up(&master->config_sem);
+
+    // wait for slave configuration to complete
+    if (wait_event_interruptible(master->config_queue,
+                master->config_state != EC_REQUEST_IN_PROGRESS)) {
+        EC_INFO("Finishing slave configuration interrupted by signal.\n");
+        goto out_allow;
+    }
+
+    if (master->debug_level)
+        EC_DBG("Waiting for pending slave configuration returned.\n");
+
+    down(&master->scan_sem);
+    master->allow_scan = 0; // 'lock' the slave list
+    up(&master->scan_sem);
+
+    // wait for slave scan to complete
+    if (wait_event_interruptible(master->scan_queue,
+                master->scan_state != EC_REQUEST_IN_PROGRESS)) {
+        EC_INFO("Waiting for slave scan interrupted by signal.\n");
+        goto out_allow;
+    }
+
+    if (master->debug_level)
+        EC_DBG("Waiting for pending slave scan returned.\n");
+
+    // set states for all slaves
     list_for_each_entry(slave, &master->slaves, list) {
         ec_slave_request_state(slave, EC_SLAVE_STATE_PREOP);
     }
 
-    master->eoe_checked = 0; // allow starting EoE again
+    if (master->debug_level)
+        EC_DBG("Switching to operation mode.\n");
+
+    master->mode = EC_MASTER_MODE_OPERATION;
     master->pdo_slaves_offline = 0; // assume all PDO slaves online
-    master->injection_seq_fsm = 0;
-    master->injection_seq_rt = 0;
-
     return 0;
-
- out_idle:
-    master->mode = EC_MASTER_MODE_IDLE;
-    if (ec_master_thread_start(master)) {
-        EC_WARN("Failed to start master thread again!\n");
-    }
+    
+out_allow:
+    master->allow_scan = 1;
+    master->allow_config = 1;
     return -1;
 }
 
@@ -461,73 +468,35 @@
 
 /**
  * Transition function from OPERATION to IDLE mode.
-*/
+ */
 
 void ec_master_leave_operation_mode(ec_master_t *master
                                     /**< EtherCAT master */)
 {
     ec_slave_t *slave;
-    ec_fsm_master_t *fsm = &master->fsm;
-    ec_fsm_slave_t fsm_slave;
-
-    ec_master_eoe_stop(master); // stop EoE timer
-    master->eoe_checked = 1; // prevent from starting again by FSM
-    ec_master_thread_stop(master); // stop master thread
-    master->injection_seq_fsm = 0;
-    master->injection_seq_rt = 0;
-
-    // wait for FSM datagram
-    if (master->fsm_datagram.state == EC_DATAGRAM_SENT) {
-        // active waiting
-        while (get_cycles() - master->fsm_datagram.cycles_sent
-               < (cycles_t) EC_IO_TIMEOUT /* us */ * (cpu_khz / 1000));
-        ecrt_master_receive(master);
-    }
-
-    // finish running master FSM
-    if (ec_fsm_master_running(fsm)) {
-        while (ec_fsm_master_exec(fsm)) {
-            ec_master_queue_datagram(master, &master->fsm_datagram);
-            ec_master_sync_io(master);
-        }
-    }
-
-    ec_fsm_slave_init(&fsm_slave, &master->fsm_datagram);
+
+    master->mode = EC_MASTER_MODE_IDLE;
+
+    ec_master_eoe_stop(master);
+    ec_master_thread_stop(master);
+    
+    master->request_cb = ec_master_request_cb;
+    master->release_cb = ec_master_release_cb;
+    master->cb_data = master;
     
     // set states for all slaves
     list_for_each_entry(slave, &master->slaves, list) {
         ec_slave_reset(slave);
         ec_slave_request_state(slave, EC_SLAVE_STATE_PREOP);
-
-        // don't try to set PREOP for slaves that don't respond,
-        // because of 3 second timeout.
-        if (slave->online_state == EC_SLAVE_OFFLINE) {
-            if (master->debug_level)
-                EC_DBG("Skipping to configure offline slave %i.\n",
-                        slave->ring_position);
-            continue;
-        }
-
-        ec_fsm_slave_start_conf(&fsm_slave, slave);
-        while (ec_fsm_slave_exec(&fsm_slave)) {
-            ec_master_queue_datagram(master, &master->fsm_datagram);
-            ec_master_sync_io(master);
-        }
-    }
-
-    ec_fsm_slave_clear(&fsm_slave);
+    }
 
     ec_master_destroy_domains(master);
-
-    master->request_cb = ec_master_request_cb;
-    master->release_cb = ec_master_release_cb;
-    master->cb_data = master;
-
-    master->eoe_checked = 0; // allow EoE again
-
-    master->mode = EC_MASTER_MODE_IDLE;
-    if (ec_master_thread_start(master)) {
-        EC_WARN("Failed to start master thread!\n");
+    
+    master->allow_scan = 1;
+    master->allow_config = 1;
+
+    if (ec_master_thread_start(master, ec_master_idle_thread)) {
+        EC_WARN("Failed to restart master thread!\n");
     }
 }
 
@@ -811,7 +780,7 @@
     daemonize("EtherCAT-IDLE");
     allow_signal(SIGTERM);
 
-    while (!signal_pending(current) && master->mode == EC_MASTER_MODE_IDLE) {
+    while (!signal_pending(current)) {
         cycles_start = get_cycles();
 
         if (ec_fsm_master_running(&master->fsm)) {
@@ -850,6 +819,8 @@
     }
     
     master->thread_id = 0;
+    if (master->debug_level)
+        EC_DBG("Master IDLE thread exiting...\n");
     complete_and_exit(&master->thread_exit, 0);
 }
 
@@ -866,9 +837,7 @@
     daemonize("EtherCAT-OP");
     allow_signal(SIGTERM);
 
-    while (!signal_pending(current) &&
-            master->mode == EC_MASTER_MODE_OPERATION) {
-
+    while (!signal_pending(current)) {
         if (master->injection_seq_rt != master->injection_seq_fsm ||
                 master->fsm_datagram.state == EC_DATAGRAM_SENT ||
                 master->fsm_datagram.state == EC_DATAGRAM_QUEUED)
@@ -902,6 +871,8 @@
     }
     
     master->thread_id = 0;
+    if (master->debug_level)
+        EC_DBG("Master OP thread exiting...\n");
     complete_and_exit(&master->thread_exit, 0);
 }
 
@@ -1455,8 +1426,6 @@
 {
     uint32_t domain_offset;
     ec_domain_t *domain;
-    ec_fsm_slave_t fsm_slave;
-    ec_slave_t *slave;
 
     // allocate all domains
     domain_offset = 0;
@@ -1468,30 +1437,37 @@
         domain_offset += domain->data_size;
     }
 
-    ec_fsm_slave_init(&fsm_slave, &master->fsm_datagram);
-
-    // configure all slaves
-    list_for_each_entry(slave, &master->slaves, list) {
-        ec_fsm_slave_start_conf(&fsm_slave, slave);
-        while (ec_fsm_slave_exec(&fsm_slave)) { 
-            ec_master_queue_datagram(master, &master->fsm_datagram);
-            ec_master_sync_io(master);
-        }
-
-        if (!ec_fsm_slave_success(&fsm_slave)) {
-            ec_fsm_slave_clear(&fsm_slave);
-            EC_ERR("Failed to configure slave %i!\n", slave->ring_position);
-            return -1;
-        }
-    }
-
-    ec_fsm_slave_clear(&fsm_slave);
+    // request slave configuration
+    down(&master->config_sem);
+    master->allow_config = 1; // request the current configuration
+    master->config_state = EC_REQUEST_IN_PROGRESS;
+    up(&master->config_sem);
+
+    // wait for configuration to complete
+    if (wait_event_interruptible(master->config_queue,
+                master->config_state != EC_REQUEST_IN_PROGRESS)) {
+        EC_INFO("Waiting for configuration interrupted by signal.\n");
+        return -1;
+    }
+
+    if (master->config_state != EC_REQUEST_COMPLETE) {
+        EC_ERR("Failed to configure slaves.\n");
+        return -1;
+    }
+    
+    // restart EoE process and master thread with new locking
+    ec_master_eoe_stop(master);
+    ec_master_thread_stop(master);
+
     ec_master_prepare(master); // prepare asynchronous IO
 
     if (master->debug_level)
         EC_DBG("FSM datagram is %x.\n", (unsigned int) &master->fsm_datagram);
 
-    if (ec_master_thread_start(master)) {
+    master->injection_seq_fsm = 0;
+    master->injection_seq_rt = 0;
+    
+    if (ec_master_thread_start(master, ec_master_operation_thread)) {
         EC_ERR("Failed to start master thread!\n");
         return -1;
     }
@@ -1502,38 +1478,6 @@
 /*****************************************************************************/
 
 /**
-   Sends queued datagrams and waits for their reception.
-*/
-
-void ec_master_sync_io(ec_master_t *master /**< EtherCAT master */)
-{
-    ec_datagram_t *datagram;
-    unsigned int datagrams_sent;
-
-    // send all datagrams
-    ecrt_master_send(master);
-
-    while (1) { // active waiting
-        schedule(); // schedule other processes while waiting.
-        ecrt_master_receive(master); // receive and dequeue datagrams
-
-        // count number of datagrams still waiting for response
-        datagrams_sent = 0;
-        list_for_each_entry(datagram, &master->datagram_queue, queue) {
-            // there may be another process that queued commands
-            // in the meantime.
-            if (datagram->state == EC_DATAGRAM_QUEUED) continue;
-            datagrams_sent++;
-        }
-
-        // abort loop if there are no more datagrams marked as sent.
-        if (!datagrams_sent) break;
-    }
-}
-
-/*****************************************************************************/
-
-/**
    Asynchronous sending of datagrams.
    \ingroup RealtimeInterface
 */
--- a/master/master.h	Mon Mar 12 18:15:06 2007 +0000
+++ b/master/master.h	Mon Mar 12 18:21:42 2007 +0000
@@ -112,6 +112,20 @@
 
     struct list_head slaves; /**< list of slaves on the bus */
     unsigned int slave_count; /**< number of slaves on the bus */
+    
+    ec_request_state_t scan_state; /**< current scanning state */
+    unsigned int allow_scan; /**< non-zero, if slave scanning is allowed */
+    struct semaphore scan_sem; /**< semaphore protecting the scan_state
+                                 variable and the allow_scan flag */
+    wait_queue_head_t scan_queue; /**< queue for processes that wait for
+                                    slave scanning */
+
+    ec_request_state_t config_state; /**< state of slave configuration */
+    unsigned int allow_config; /**< non-zero, if slave scanning is allowed */
+    struct semaphore config_sem; /**< semaphore protecting the config_state
+                                   variable and the allow_config flag */
+    wait_queue_head_t config_queue; /**< queue for processes that wait for
+                                      slave configuration */
 
     struct list_head datagram_queue; /**< datagram queue */
     uint8_t datagram_index; /**< current datagram index */
--- a/master/slave.c	Mon Mar 12 18:15:06 2007 +0000
+++ b/master/slave.c	Mon Mar 12 18:21:42 2007 +0000
@@ -113,7 +113,7 @@
 
     slave->master = master;
 
-    slave->requested_state = EC_SLAVE_STATE_UNKNOWN;
+    slave->requested_state = EC_SLAVE_STATE_PREOP;
     slave->current_state = EC_SLAVE_STATE_UNKNOWN;
     slave->self_configured = 0;
     slave->error_flag = 0;