Detect a valid of serial8250 ports

Usually, a Linux kernel reserves a places for the non-PnP serial
devices, for example, such as ttyS[0-4/14]. In case the system has not a
HW devices which are attached to this places, then these devices will be
stubs and present as usual serial ports. Thus, we can know about a
validity of these devices only in attempt to open them and to query a
type of.

Note: This patch is theoretical, because are not tested for a valid 8250
devices.

Task-number: QTBUG-32024
Change-Id: I313145caadfeeee4d5fe3c8e16c1bcf4ae79214d
Reviewed-by: Sergey Belyashov <Sergey.Belyashov@gmail.com>

2 files changed, 29 insertions, 8 deletions

diff --git a/src/serialport/qserialport_unix_p.h b/src/serialport/qserialport_unix_p.h
index 75e6004..5ec6653 100644
--- a/src/serialport/qserialport_unix_p.h
+++ b/src/serialport/qserialport_unix_p.h
@@ -82,6 +82,7 @@ struct serial_struct {
 };
 #define ASYNC_SPD_CUST  0x0030
 #define ASYNC_SPD_MASK  0x1030
+#define PORT_UNKNOWN    0
 #endif
 
 QT_BEGIN_NAMESPACE
diff --git a/src/serialport/qserialportinfo_unix.cpp b/src/serialport/qserialportinfo_unix.cpp
index 6a27d41..58eb62b 100644
--- a/src/serialport/qserialportinfo_unix.cpp
+++ b/src/serialport/qserialportinfo_unix.cpp
@@ -42,6 +42,7 @@
 #include <QtCore/qdir.h>
 #include <QtCore/qscopedpointer.h>
 
+#include <private/qcore_unix_p.h>
 
 #include <errno.h>
 #include <sys/types.h> // kill
@@ -113,6 +114,24 @@ static bool isSerial8250Driver(const QString &driverName)
     return (driverName == QStringLiteral("serial8250"));
 }
 
+static bool isValidSerial8250(const QString &systemLocation)
+{
+#ifdef Q_OS_LINUX
+    const mode_t flags = O_RDWR | O_NONBLOCK | O_NOCTTY;
+    const int fd = qt_safe_open(systemLocation.toLocal8Bit().constData(), flags);
+    if (fd != -1) {
+        struct serial_struct serinfo;
+        const int retval = ::ioctl(fd, TIOCGSERIAL, &serinfo);
+        qt_safe_close(fd);
+        if (retval != -1 && serinfo.type != PORT_UNKNOWN)
+            return true;
+    }
+#else
+    Q_UNUSED(systemLocation);
+#endif
+    return false;
+}
+
 static QString ueventProperty(const QDir &targetDir, const QByteArray &pattern)
 {
     QFile f(QFileInfo(targetDir, QStringLiteral("uevent")).absoluteFilePath());
@@ -200,17 +219,18 @@ QList<QSerialPortInfo> availablePortsBySysfs(bool &ok)
         QDir targetDir(fileInfo.symLinkTarget());
 
         const QString driverName = deviceDriver(targetDir);
-        if (driverName.isEmpty() || isSerial8250Driver(driverName))
-            continue;
-
-        const QString portName = deviceName(targetDir);
-        if (portName.isEmpty())
+        if (driverName.isEmpty())
             continue;
 
         QSerialPortInfoPrivate priv;
 
-        priv.portName = portName;
-        priv.device = QSerialPortInfoPrivate::portNameToSystemLocation(portName);
+        priv.portName = deviceName(targetDir);
+        if (priv.portName.isEmpty())
+            continue;
+
+        priv.device = QSerialPortInfoPrivate::portNameToSystemLocation(priv.portName);
+        if (isSerial8250Driver(driverName) && !isValidSerial8250(priv.device))
+            continue;
 
         do {
             if (priv.description.isEmpty())
@@ -366,7 +386,7 @@ QList<QSerialPortInfo> availablePortsByUdev(bool &ok)
 
         if (parentdev) {
             const QString driverName = deviceDriver(parentdev);
-            if (isSerial8250Driver(driverName))
+            if (isSerial8250Driver(driverName) && !isValidSerial8250(priv.portName))
                 continue;
             priv.description = deviceDescription(dev.data());
             priv.manufacturer = deviceManufacturer(dev.data());