Embedded linux usb-ftdi serial port read issue - serial-port

Question

I have a TI Cortex-based Pengwyn board running embedded Linux that I am trying to use to read raw serial data from a USB-ftdi peripheral so I can process it into data packets.
To do this I've written a simple program (using Qt) and the termios framework. This works no problem on my desktop (Ubuntu VM) machine - it opens /dev/ttyUSB0, configures the serial port, reads and process the data without problems.
I run into problems when I run the same program (cross-compiled for arm obviously) on the pengwyn board... The read() function call does not populate the buffer - although it returns a non-error value, indicating the number of bytes that have been read???
(I also had to rebuilt the linux kernel for the pengwyn board to include teh USB-ftdi serial driver.)
I suspect it is a target configuration issue but I have compared the file permissions and termios settings between both the platforms and they look okay. I am new to this platform and serial/termios stuff so I have undoubtedly over-looked something but I've looked through the "Serial Programming Guide for POSIX Operating Systems" and searched for similar posts regarding arm and usb-ftdi read problems but have yet to find anything.
Any suggestions/observations?
Relevant excerpts from test program:
void Test::startRx(void)
{
bool retval = false;
m_fd = open(m_port.toLocal8Bit(),O_RDONLY |O_NOCTTY | O_NDELAY);
if (m_fd == -1)
{
qDebug() << "Unable to open: " << m_port.toLocal8Bit() << strerror(errno);
}
else
{
m_isConnected = true;
qDebug() << m_port.toLocal8Bit() << "is open...";
fcntl(m_fd, F_SETFL, 0);
struct termios options;
if (tcgetattr(m_fd, &options)!=0)
{
qDebug() << "tcgetattr() failed";
}
//Set the baud rates to 9600
cfsetispeed(&options, B9600);
cfsetospeed(&options, B9600);
//Enable the receiver and set local mode
options.c_cflag |= (CLOCAL | CREAD);
//Set character size
options.c_cflag &= ~CSIZE; /* Mask the character size bits */
options.c_cflag |= CS8; /* Select 8 data bits */
//No parity 8N1:
options.c_cflag &= ~PARENB;
options.c_cflag &= ~CSTOPB;
options.c_cflag &= ~CSIZE;
options.c_cflag |= CS8;
//Disable hardware flow control
options.c_cflag &= ~CRTSCTS;
//Disable software flow control
options.c_iflag &= ~(IXON | IXOFF | IXANY);
//Raw output
options.c_oflag &= ~OPOST;
//Raw input
options.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
//Set the new options for the port...
tcsetattr(m_fd, TCSANOW, &options);
int status;
ioctl(m_fd, TIOCMGET, &status );
qDebug() << "current modem status:" << status;
QThread* m_reader_thread = new QThread;
m_serial_port_reader = new SerialPortReader(0, m_fd);
if (m_serial_port_reader)
{
qDebug() << "creating serial port reader thread...";
m_serial_port_reader->moveToThread(m_reader_thread);
connect(m_serial_port_reader, SIGNAL(notifyRxPacketData(QByteArray *)), this, SLOT(processRxPacketData(QByteArray*)));
//connect(m_serial_port_reader, SIGNAL(error(QString)), this, SLOT(errorString(QString)));
connect(m_reader_thread, SIGNAL(started()), m_serial_port_reader, SLOT(process()));
connect(m_serial_port_reader, SIGNAL(finished()), m_reader_thread, SLOT(quit()));
connect(m_serial_port_reader, SIGNAL(finished()), m_serial_port_reader, SLOT(quit()));
connect(m_reader_thread, SIGNAL(finished()), m_reader_thread, SLOT(deleteLater()));
m_reader_thread->start();
retval = true;
}
....
void SerialPortReader::readData(int i)
{
m_socket_notifier->setEnabled(false);
if (i == m_fd)
{
unsigned char buf[BUFSIZE] = {0};
int bytesRead = read(m_fd, buf, BUFSIZE);
//qDebug() << Q_FUNC_INFO << "file decriptor:" << m_fd << ", no. bytes read:" << bytesRead;
if (bytesRead < 0)
{
qDebug() << Q_FUNC_INFO << "serial port read error";
return;
}
// if the device "disappeared", e.g. from USB, we get a read event for 0 bytes
else if (bytesRead == 0)
{
//qDebug() << Q_FUNC_INFO << "finishing!!!";
return;
}
//process data...
}
m_socket_notifier->setEnabled(true);
}