diff --git a/DSView/pv/appcontrol.cpp b/DSView/pv/appcontrol.cpp
index 444d68ba..618876ce 100644
--- a/DSView/pv/appcontrol.cpp
+++ b/DSView/pv/appcontrol.cpp
@@ -87,7 +87,7 @@ bool AppControl::Init()
     QString dir = GetDecodeScriptDir();   
     strcpy(path, dir.toUtf8().data());
 
-    dsv_info("decode script files directory: \"%s\"", dir.toUtf8().data());
+    dsv_info("Decode script files directory:\"%s\"", dir.toUtf8().data());
 
     // Initialise libsigrokdecode
     if (srd_init(path) != SRD_OK)
diff --git a/DSView/pv/mainwindow.cpp b/DSView/pv/mainwindow.cpp
index c1019715..627331e5 100644
--- a/DSView/pv/mainwindow.cpp
+++ b/DSView/pv/mainwindow.cpp
@@ -313,8 +313,10 @@ namespace pv
     {
         try
         {
-            if (strncmp(_device_agent->name().toUtf8(), "virtual", 7))
+            if (_device_agent->is_hardware()){
                 session_save();
+            }
+
             _session->set_file(file_name);
         }
         catch (QString e)
@@ -414,8 +416,7 @@ namespace pv
     }
 
     void MainWindow::session_save()
-    {
-        QDir dir;
+    { 
 #if QT_VERSION >= 0x050400
         QString path = QStandardPaths::writableLocation(QStandardPaths::AppDataLocation);
 #else
@@ -428,28 +429,40 @@ namespace pv
             return;
         }
 
-        AppConfig &app = AppConfig::Instance();
+        AppConfig &app = AppConfig::Instance();        
 
-        if (dir.mkpath(path))
-        {
-            dir.cd(path);
-            QString driver_name = _device_agent->name();
-            QString mode_name = QString::number(_device_agent->get_work_mode());
-            QString lang_name = ".ses" + QString::number(app._frameOptions.language);
-            QString file_name = dir.absolutePath() + "/" +
-                                driver_name + mode_name +
-                                lang_name + ".dsc";
-            if (strncmp(driver_name.toUtf8(), "virtual", 7) &&
-                !file_name.isEmpty())
-            {
-                on_store_session(file_name);
-            }
+        if (_device_agent->is_hardware()){
+            QString sessionFile = genSessionFileName();
+            on_store_session(sessionFile);
         }
 
         app._frameOptions.windowState = saveState();
         app.SaveFrame();
     }
 
+    QString MainWindow::genSessionFileName()
+    {
+#if QT_VERSION >= 0x050400
+        QString path = QStandardPaths::writableLocation(QStandardPaths::AppDataLocation);
+#else
+        QString path = QStandardPaths::writableLocation(QStandardPaths::DataLocation);
+#endif
+
+        AppConfig &app = AppConfig::Instance();
+
+        QDir dir(path);
+        if (dir.exists() == false){
+            dir.mkpath(path);
+        } 
+
+        QString driver_name = _device_agent->driver_name();
+        QString mode_name = QString::number(_device_agent->get_work_mode());
+        QString lang_name = ".ses" + QString::number(app._frameOptions.language);
+        QString file_name = dir.absolutePath() + "/" + driver_name + mode_name + lang_name + ".dsc";
+
+        return file_name;
+    }
+
     void MainWindow::closeEvent(QCloseEvent *event)
     {
         // not used, refer to closeEvent of mainFrame
@@ -565,17 +578,29 @@ namespace pv
 
     bool MainWindow::on_load_session(QString name)
     {
-        QFile sessionFile(name);
+        if (name == ""){
+            dsv_err("%s", "Session file name is empty.");
+            assert(false);
+        }
+
+        dsv_info("Load session file: \"%s\"", name.toLocal8Bit().data());
+
+        QFile sf(name);
         bool bDone;
 
-        if (!sessionFile.open(QIODevice::ReadOnly))
-        {
-            dsv_warn("%s", "Warning: Couldn't open session file!");
+        if (!sf.exists()){
+            dsv_warn("Warning: session file is not exists: \"%s\"", name.toLocal8Bit().data());
             return false;
         }
 
-        QString sessionData = QString::fromUtf8(sessionFile.readAll());
-        QJsonDocument sessionDoc = QJsonDocument::fromJson(sessionData.toUtf8());
+        if (!sf.open(QIODevice::ReadOnly))
+        {
+            dsv_warn("%s", "Warning: Couldn't open session file to load!");
+            return false;
+        }
+
+        QString sdata = QString::fromUtf8(sf.readAll());
+        QJsonDocument sessionDoc = QJsonDocument::fromJson(sdata.toUtf8());
 
         _protocol_widget->del_all_protocol();
         return load_session_json(sessionDoc, bDone);
@@ -920,6 +945,13 @@ namespace pv
 
     bool MainWindow::on_store_session(QString name)
     {
+        if (name == ""){
+            dsv_err("%s", "Session file name is empty.");
+            assert(false);
+        }
+
+        dsv_info("Store session file: \"%s\"", name.toLocal8Bit().data());
+
         QFile sessionFile(name);
         if (!sessionFile.open(QIODevice::WriteOnly | QIODevice::Text))
         {
@@ -931,8 +963,10 @@ namespace pv
         encoding::set_utf8(outStream);
 
         QJsonObject sessionVar;
-        if (!gen_session_json(sessionVar))
+        if (!gen_session_json(sessionVar)){
             return false;
+        }
+
         QJsonDocument sessionDoc(sessionVar);
         outStream << QString::fromUtf8(sessionDoc.toJson());
         sessionFile.close();
@@ -943,7 +977,10 @@ namespace pv
     {
         QJsonObject sessionVar;
         if (!gen_session_json(sessionVar))
+        {
             return false;
+        }
+
         QJsonDocument sessionDoc(sessionVar);
         QString data = QString::fromUtf8(sessionDoc.toJson());
         str.append(data.toLocal8Bit().data());
@@ -1378,38 +1415,20 @@ namespace pv
     void MainWindow::load_device_config()
     {
         int lang = AppConfig::Instance()._frameOptions.language;
-        QString name = _device_agent->name();
         int mode = _device_agent->get_work_mode();
 
         if (_device_agent->is_hardware())
-        {
-
-#if QT_VERSION >= 0x050400
-            QDir dir(QStandardPaths::writableLocation(QStandardPaths::AppDataLocation));
-#else
-            QDir dir(QStandardPaths::writableLocation(QStandardPaths::DataLocation));
-#endif
-            if (dir.exists())
-            {
-                QString str = dir.absolutePath() + "/";
-                QString lang_name = ".ses" + QString::number(lang);
-                QString ses_name = str +
-                                   name +
-                                   QString::number(mode) +
-                                   lang_name + ".dsc";
-                on_load_session(ses_name);
-            }
+        { 
+            QString sessionFile = genSessionFileName();
+            on_load_session(sessionFile);
         }
-        else
+        else if (_device_agent->is_demo())
         {
             QDir dir(GetResourceDir());
             if (dir.exists())
             {
                 QString str = dir.absolutePath() + "/";
-                QString ses_name = str +
-                                   name +
-                                   QString::number(mode) +
-                                   ".dsc";
+                QString ses_name = str + _device_agent->driver_name() + QString::number(mode) + ".dsc";
                 if (QFileInfo(ses_name).exists())
                     on_load_session(ses_name);
             }
diff --git a/DSView/pv/mainwindow.h b/DSView/pv/mainwindow.h
index abb24783..72b16bee 100644
--- a/DSView/pv/mainwindow.h
+++ b/DSView/pv/mainwindow.h
@@ -94,7 +94,8 @@ private:
 	void setup_ui();
     void retranslateUi(); 
     bool eventFilter(QObject *object, QEvent *event);
-    bool load_session_json(QJsonDocument json, bool &haveDecoder);  
+    bool load_session_json(QJsonDocument json, bool &haveDecoder);
+    QString genSessionFileName();
 
 public slots: 
     void switchTheme(QString style);
diff --git a/DSView/pv/sigsession.cpp b/DSView/pv/sigsession.cpp
index 12d5a0e6..914fc365 100644
--- a/DSView/pv/sigsession.cpp
+++ b/DSView/pv/sigsession.cpp
@@ -203,15 +203,15 @@ namespace pv
         _device_agent.update();
 
         if (_device_agent.is_file())
-            dsv_info("%s\"%s\"", "Switch to file: ", _device_agent.name().toUtf8().data());
+            dsv_info("Switch to file \"%s\" done.", _device_agent.name().toUtf8().data());
         else
-            dsv_info("%s\"%s\"", "Switch to device: ", _device_agent.name().toUtf8().data());
+            dsv_info("Switch to device \"%s\" done.", _device_agent.name().toUtf8().data());
 
         _device_status = ST_INIT;
 
-        RELEASE_ARRAY(_group_traces);
-
         clear_all_decoder();
+
+        RELEASE_ARRAY(_group_traces);        
         init_signals();
 
         _cur_snap_samplerate = _device_agent.get_sample_rate();
diff --git a/DSView/pv/sigsession.h b/DSView/pv/sigsession.h
index da923a9a..596d4887 100644
--- a/DSView/pv/sigsession.h
+++ b/DSView/pv/sigsession.h
@@ -162,8 +162,7 @@ public:
     std::vector<view::GroupSignal*>& get_group_signals();
 
     bool add_decoder(srd_decoder *const dec, bool silent, DecoderStatus *dstatus, 
-            std::list<pv::data::decode::Decoder*> &sub_decoders);
-
+                        std::list<pv::data::decode::Decoder*> &sub_decoders);
     int get_trace_index_by_key_handel(void *handel);
     void remove_decoder(int index);
     void remove_decoder_by_key_handel(void *handel); 
diff --git a/DSView/pv/view/logicsignal.cpp b/DSView/pv/view/logicsignal.cpp
index 5b517c70..0a6581cc 100644
--- a/DSView/pv/view/logicsignal.cpp
+++ b/DSView/pv/view/logicsignal.cpp
@@ -28,6 +28,7 @@
 #include "../data/logicsnapshot.h"
 #include "view.h"
 #include "../dsvdef.h"
+#include "../log.h"
 
 using namespace std;
 
@@ -137,7 +138,9 @@ void LogicSignal::paint_mid(QPainter &p, int left, int right, QColor fore, QColo
 		return;
   
     auto snapshot =  const_cast<data::LogicSnapshot*>(snapshots.front());
-    if (snapshot->empty() || !snapshot->has_data(_probe->index))
+    if (snapshot->empty())
+        return;
+    if (!snapshot->has_data(_probe->index))
         return;
 
     const int64_t last_sample =  snapshot->get_sample_count() - 1;
@@ -148,8 +151,10 @@ void LogicSignal::paint_mid(QPainter &p, int left, int right, QColor fore, QColo
     const double end = (offset + width + 1) * samples_per_pixel;
     const uint64_t end_index = min(max((int64_t)ceil(end), (int64_t)0), last_sample);
     const uint64_t start_index = max((uint64_t)floor(start), (uint64_t)0);
+    
     if (start_index > end_index)
         return;
+
     width = min(width, (uint16_t)ceil((end_index + 1)/samples_per_pixel - offset));
     const uint16_t max_togs = width / TogMaxScale;
 
diff --git a/DSView/pv/view/viewport.cpp b/DSView/pv/view/viewport.cpp
index db2f5400..652e9684 100644
--- a/DSView/pv/view/viewport.cpp
+++ b/DSView/pv/view/viewport.cpp
@@ -199,20 +199,21 @@ void Viewport::paintEvent(QPaintEvent *event)
 }
 
 void Viewport::paintSignals(QPainter &p, QColor fore, QColor back)
-{
+{ 
     std::vector<Trace*> traces;
     _view.get_traces(_type, traces);
 
     if (_view.session().get_device()->get_work_mode() == LOGIC) {
 
-        for(auto &t : traces)
+        for(auto t : traces)
         {
             assert(t); 
 
             if (t->enabled())
                 t->paint_mid(p, 0, t->get_view_rect().right(), fore, back);
         }
-    } else {
+    } 
+    else {
         if (_view.scale() != _curScale ||
             _view.offset() != _curOffset ||
             _view.get_signalHeight() != _curSignalHeight ||
@@ -225,21 +226,13 @@ void Viewport::paintSignals(QPainter &p, QColor fore, QColor back)
             pixmap.fill(Qt::transparent);
 
             QPainter dbp(&pixmap);
-            //dbp.begin(this);
-            for(auto &t : traces)
+           
+            for(auto t : traces)
             {
                 assert(t);
 
-                /*
-                auto ptr = t->get();
-                if (ptr->enabled()){
-                     ptr->paint_mid(dbp, 0, t->get_view_rect().right(), fore, back); 
-                     continue;
-                }
-               */
-
                 if (t->enabled())
-                    t->paint_mid(dbp, 0, t->get_view_rect().right(), fore, back);      
+                    t->paint_mid(dbp, 0, t->get_view_rect().right(), fore, back); 
             }
             _need_update = false;
         }
diff --git a/libsigrok4DSL/dsdevice.c b/libsigrok4DSL/dsdevice.c
index 8f168418..de19b5ac 100644
--- a/libsigrok4DSL/dsdevice.c
+++ b/libsigrok4DSL/dsdevice.c
@@ -46,7 +46,9 @@ SR_PRIV struct sr_channel *sr_channel_new(uint16_t index, int type, gboolean ena
 {
 	struct sr_channel *probe;
 
-	if (!(probe = g_try_malloc0(sizeof(struct sr_channel)))) {
+	probe = g_try_malloc0(sizeof(struct sr_channel));
+
+	if (probe == NULL) {
 		sr_err("Probe malloc failed.");
 		return NULL;
 	}
diff --git a/libsigrok4DSL/hardware/DSL/dsl.c b/libsigrok4DSL/hardware/DSL/dsl.c
index 8c2ae7ea..a89d7844 100644
--- a/libsigrok4DSL/hardware/DSL/dsl.c
+++ b/libsigrok4DSL/hardware/DSL/dsl.c
@@ -310,8 +310,8 @@ static int hw_dev_open(struct sr_dev_driver *di, struct sr_dev_inst *sdi)
 
     if (sdi->status == SR_ST_ACTIVE) {
         /* Device is already in use. */
-        sr_info("Device is actived, can't to open, handle:%p", usb->usb_dev);
-        return SR_ERR;
+        sr_detail("The usb device is opened, handle:%p", usb->usb_dev);
+        return SR_OK;
     }
 
     if (sdi->status == SR_ST_INITIALIZING) {
@@ -319,7 +319,7 @@ static int hw_dev_open(struct sr_dev_driver *di, struct sr_dev_inst *sdi)
     }
     dev_handel = usb->usb_dev;
 
-    sr_info("Open device instance, handle: %p", dev_handel);
+    sr_info("Open usb device instance, handle: %p", dev_handel);
 
     if (libusb_open(dev_handel, &usb->devhdl) != 0){
         sr_err("Failed to open device: %s, handle:%p",
diff --git a/libsigrok4DSL/hardware/DSL/dslogic.c b/libsigrok4DSL/hardware/DSL/dslogic.c
index 245c7a6c..772e236b 100644
--- a/libsigrok4DSL/hardware/DSL/dslogic.c
+++ b/libsigrok4DSL/hardware/DSL/dslogic.c
@@ -1369,10 +1369,12 @@ static int dev_acquisition_start(struct sr_dev_inst *sdi, void *cb_data)
     /* Stop Previous GPIF acquisition */
     wr_cmd.header.dest = DSL_CTL_STOP;
     wr_cmd.header.size = 0;
+    
     if ((ret = command_ctl_wr(usb->devhdl, wr_cmd)) != SR_OK) {
         sr_err("%s: Stop DSLogic acquisition failed!", __func__);
         return ret;
-    } else {
+    } 
+    else {
         sr_info("%s: Stop Previous DSLogic acquisition!", __func__);
     }
 
diff --git a/libsigrok4DSL/lib_main.c b/libsigrok4DSL/lib_main.c
index 0d870703..8729c209 100644
--- a/libsigrok4DSL/lib_main.c
+++ b/libsigrok4DSL/lib_main.c
@@ -216,7 +216,7 @@ SR_API void ds_set_firmware_resource_dir(const char *dir)
 			DS_RES_PATH[len + 1] = 0;
 		}
 
-		sr_info("Firmware resource path:\"%s\"", DS_RES_PATH);
+		sr_info("Firmware resource directory:\"%s\"", DS_RES_PATH);
 	}
 }
 
@@ -310,7 +310,7 @@ SR_API int ds_active_device(ds_device_handle handle)
 	}
 	ret = SR_OK;
 
-	sr_info("%s", "Begin set current device.");
+	sr_info("%s", "Start activating device.");
 
 	if (ds_is_collecting())
 	{
@@ -348,7 +348,10 @@ SR_API int ds_active_device(ds_device_handle handle)
 				sr_err("%s", "Please call ds_set_firmware_resource_dir() to set the firmware resource path.");
 			}
 
-			sr_info("Switch \"%s\" to current device.", dev->name);
+			if (dev->dev_type == DEV_TYPE_FILELOG)
+				sr_info("virtual device name: \"%s\".", dev->name);
+			else
+				sr_info("device name: \"%s\".", dev->name);
 
 			if (open_device_instance(dev) == SR_OK)
 			{
@@ -365,7 +368,7 @@ SR_API int ds_active_device(ds_device_handle handle)
 
 	pthread_mutex_unlock(&lib_ctx.mutext);
 
-	sr_info("%s", "End of setting current device.");
+	sr_info("%s", "Activating device end.");
 
 	if (!bFind)
 	{
diff --git a/libsigrok4DSL/session_driver.c b/libsigrok4DSL/session_driver.c
index 504ddac4..168b29a7 100644
--- a/libsigrok4DSL/session_driver.c
+++ b/libsigrok4DSL/session_driver.c
@@ -435,28 +435,30 @@ static int dev_clear(void)
 static int dev_open(struct sr_dev_inst *sdi)
 {
     int ret;
+    struct session_vdev *vdev;
 
-    if (sdi->priv == NULL)
-    {
-        sdi->priv = g_try_malloc0(sizeof(struct session_vdev));
-        if (sdi->priv == NULL)
-        {
-            sr_err("%s: sdi->priv malloc failed", __func__);
-            return SR_ERR_MALLOC;
-        }
+    assert(sdi);
+
+    if (sdi->status == SR_ST_ACTIVE){
+        // Is opened.
+        return SR_OK;
     }
 
-    struct session_vdev *vdev;
+    assert(sdi->priv == NULL);
+
+    sdi->priv = g_try_malloc0(sizeof(struct session_vdev));
+    if (sdi->priv == NULL)
+    {
+        sr_err("%s: sdi->priv malloc failed", __func__);
+        return SR_ERR_MALLOC;
+    }
     vdev = sdi->priv;
 
+    vdev->buf = g_try_malloc(CHUNKSIZE + sizeof(uint64_t));
     if (vdev->buf == NULL)
     {
-        vdev->buf = g_try_malloc(CHUNKSIZE + sizeof(uint64_t));
-        if (vdev->buf == NULL)
-        {
-            sr_err("%s: vdev->buf malloc failed", __func__);
-            return SR_ERR_MALLOC;
-        }
+        sr_err("%s: vdev->buf malloc failed", __func__);
+        return SR_ERR_MALLOC;
     }
 
     vdev->trig_pos = 0;
@@ -473,6 +475,8 @@ static int dev_open(struct sr_dev_inst *sdi)
     vdev->mstatus.measure_valid = TRUE;
     vdev->archive = NULL;
     vdev->capfile = 0;
+    
+    sdi->status = SR_ST_ACTIVE;
 
     ret = sr_load_virtual_device_session(sdi);
     if (ret != SR_OK)
@@ -494,9 +498,12 @@ static int dev_close(struct sr_dev_inst *sdi)
         g_safe_free(vdev->buf);
         g_safe_free(vdev->logic_buf);
         g_safe_free(sdi->priv);
+
+        sdi->status = SR_ST_INACTIVE;
+        return SR_OK;
     }
 
-    return SR_OK;
+    return SR_ERR_CALL_STATUS;
 }
 
 static int dev_destroy(struct sr_dev_inst *sdi)
@@ -1233,7 +1240,7 @@ SR_PRIV int sr_new_virtual_device(const char *filename, struct sr_dev_inst **out
     g_key_file_free(kf);
     g_free(metafile);
 
-    sdi = sr_dev_inst_new(mode, SR_ST_ACTIVE, NULL, NULL, NULL);
+    sdi = sr_dev_inst_new(mode, SR_ST_INACTIVE, NULL, NULL, NULL);
     sdi->driver = &session_driver;
     sdi->dev_type = DEV_TYPE_FILELOG;
 
@@ -1456,9 +1463,6 @@ static int sr_load_virtual_device_session(struct sr_dev_inst *sdi)
                 }
                 else if (!strncmp(keys[j], "probe", 5))
                 {
-                    if (!sdi)
-                        continue;
-
                     enabled_probes++;
                     tmp_u64 = strtoul(keys[j] + 5, NULL, 10);
                     /* sr_session_save() */