libgfamininet/libmininet/gfaserial.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <malloc.h>
#include <fcntl.h>
#include <errno.h>
#include <termios.h>
#include <unistd.h>
#include <ctype.h>
#include <sys/file.h>
#include "gfaserial.h"

#define min(a, b)			(((a) < (b)) ? (a) : (b))

/////////////////////////////////////////////////////////////////////////////
// https://blog.mbedded.ninja/programming/operating-systems/linux/linux-serial-ports-using-c-cpp/#everything-is-a-file
/////////////////////////////////////////////////////////////////////////////

typedef struct _GFA_SERIAL_DEVICE
{
	int fd;
	char *pszDeviceName;
	GFA_SER_CFG_PARAMS cfg;
	struct termios tty;
	struct termios ttySave;
	struct timeval tvRX;
	struct timeval tvTX;
	struct timeval tvEcho;
	struct timeval tvPurge;
}GFA_SERIAL_DEVICE, *LPGFA_SERIAL_DEVICE;
typedef const GFA_SERIAL_DEVICE *LPCGFA_SERIAL_DEVICE;

/////////////////////////////////////////////////////////////////////////////

static speed_t _MapBaudrate(uint32_t b)
{
	speed_t s;

	switch(b)
	{
	case 50:		s = B50; break;
	case 75:		s = B75; break;
	case 110:		s = B110; break;
	case 134:		s = B134; break;
	case 150:		s = B150; break;
	case 200:		s = B200; break;
	case 300:		s = B300; break;
	case 600:		s = B600; break;
	case 1200:		s = B1200; break;
	case 1800:		s = B1800; break;
	case 2400:		s = B2400; break;
	case 4800:		s = B4800; break;
	case 9600:		s = B9600; break;
	case 19200:		s = B19200; break;
	case 38400:		s = B38400; break;
	case 57600:		s = B57600; break;
	case 115200:	s = B115200; break;
	case 230400:	s = B230400; break;
	case 460800:	s = B460800; break;
	case 921600:	s = B921600; break;
	default:	    s = (speed_t)-1; break;
	}

	return s;
}

/////////////////////////////////////////////////////////////////////////////

static void _SetDefaultTimeouts(LPGFA_SERIAL_DEVICE psd)
{
	if(psd)
	{
		psd->tvRX.tv_sec		= 0;
		psd->tvRX.tv_usec		= 200000;
		psd->tvTX.tv_sec		= 0;
		psd->tvTX.tv_usec		= 100000;
		psd->tvEcho.tv_sec		= 0;
		psd->tvEcho.tv_usec		= 50000;
		psd->tvPurge.tv_sec		= 0;
		psd->tvPurge.tv_usec	= 10000;
	}
}

static void _CopyTimeval(struct timeval *ptvTo, const struct timeval *ptvFrom)
{
	ptvTo->tv_sec	= ptvFrom->tv_sec;
	ptvTo->tv_usec	= ptvFrom->tv_usec;
}

/////////////////////////////////////////////////////////////////////////////

static bool _ReadEcho(HGFADEVICE hSer, const void *pData, size_t nWritten)
{
	uint8_t b[256];
	ssize_t nRet;
	struct timeval tvSave;
	LPGFA_SERIAL_DEVICE psd = (LPGFA_SERIAL_DEVICE)hSer;
	ssize_t nLeft = (ssize_t)nWritten, nRead = 0, nToRead;
	const char *pszData = (const char*)pData;

	if(!nLeft)
		return false;
	if(	!GfaSerialGetTimeouts(hSer, &tvSave, NULL) ||
		!GfaSerialSetTimeouts(hSer, &psd->tvEcho, NULL))
		return false;

	do
	{
		nToRead = min(nLeft, (ssize_t)sizeof(b));
		if((nRet = GfaSerialReceive(hSer, b, nToRead)) <= 0)
		{
			GfaSerialSetTimeouts(hSer, &tvSave, NULL);
			return false;
		}
		if(memcmp(b, pszData, nRet))
		{
			GfaSerialSetTimeouts(hSer, &tvSave, NULL);
			return false;
		}
		pszData += nRet;
		nRead += nRet;
		nLeft = (ssize_t)nWritten - nRead;
	}
	while(nLeft > 0);

	GfaSerialSetTimeouts(hSer, &tvSave, NULL);
	return (nRead == (ssize_t)nWritten);
}

/////////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////

HGFADEVICE GfaSerialOpen(const char *pszDeviceName, LPCGFA_SER_CFG_PARAMS pscp, size_t nSizeCfgParams)
{
	if(pszDeviceName && *pszDeviceName && pscp && nSizeCfgParams >= sizeof(GFA_SER_CFG_PARAMS))
	{
		LPGFA_SERIAL_DEVICE psd = malloc(sizeof(GFA_SERIAL_DEVICE));
		memset(psd, 0, sizeof(GFA_SERIAL_DEVICE));
		
		/////////////////////////////////////////////////////////////////////
		// Open the device

		if((psd->fd = open(pszDeviceName, O_RDWR | O_NONBLOCK)) < 0)
		{
			GfaSerialClose(psd);
		    return NULL;
		}
		
		/////////////////////////////////////////////////////////////////////
		// Lock device descriptor exclusive

		if(flock(psd->fd, LOCK_EX | LOCK_NB) < 0)
		{
			GfaSerialClose(psd);
		    return NULL;
		}
		
		/////////////////////////////////////////////////////////////////////
		// Get current config and save it for restore on close

		if(tcgetattr(psd->fd, &psd->tty) != 0)
		{
			GfaSerialClose(psd);
		    return NULL;
		}

		memcpy(&psd->ttySave, &psd->tty, sizeof(struct termios));
		
		/////////////////////////////////////////////////////////////////////
		// Set new config

		if(GfaSerialSetConfig(psd, pscp, nSizeCfgParams) < 0)
		{
			GfaSerialClose(psd);
		    return NULL;
		}

		/////////////////////////////////////////////////////////////////////
		// Set deault timeouts.

		_SetDefaultTimeouts(psd);

		/////////////////////////////////////////////////////////////////////
		// Everything ok.

		psd->pszDeviceName = strdup(pszDeviceName);
		GfaSerialPurgeRXBuffer((HGFADEVICE)psd); // clear RX buffer
		return (HGFADEVICE)psd;
	}

	errno = EINVAL;
    return NULL;
}

/////////////////////////////////////////////////////////////////////////////

void GfaSerialClose(HGFADEVICE hSer)
{
	if(hSer)
	{
		int nErrno = errno;
		LPGFA_SERIAL_DEVICE psd = (LPGFA_SERIAL_DEVICE)hSer;
		if(psd->fd >= 0)
		{
			tcsetattr(psd->fd, TCSAFLUSH, &psd->ttySave);
			flock(psd->fd, LOCK_UN | LOCK_NB);
			close(psd->fd);
		}
		if(psd->pszDeviceName)
			free(psd->pszDeviceName);
		free(psd);
		errno = nErrno;
	}
}

/////////////////////////////////////////////////////////////////////////////

ssize_t GfaSerialGetConfig(HGFADEVICE hSer, LPGFA_SER_CFG_PARAMS pscp, size_t nSizeCfgParams)
{
	if(hSer && pscp && nSizeCfgParams == sizeof(GFA_SER_CFG_PARAMS))
	{
		LPGFA_SERIAL_DEVICE psd = (LPGFA_SERIAL_DEVICE)hSer;
		memcpy(pscp, &psd->cfg, sizeof(GFA_SER_CFG_PARAMS));
		return sizeof(GFA_SER_CFG_PARAMS);
	}

	errno = EINVAL;
    return -1;
}

/////////////////////////////////////////////////////////////////////////////

int GfaSerialSetConfig(HGFADEVICE hSer, LPCGFA_SER_CFG_PARAMS pscp, size_t nSizeCfgParams)
{
	if(hSer && pscp && nSizeCfgParams == sizeof(GFA_SER_CFG_PARAMS))
	{
		int nRet;
		speed_t s;
		LPGFA_SERIAL_DEVICE psd = (LPGFA_SERIAL_DEVICE)hSer;

		/////////////////////////////////////////////////////////////////////
		// Baud Rate

		if((s = _MapBaudrate(pscp->baud)) == (speed_t)-1)
		{
			errno = EINVAL;
		    return -1;
		}

		if(	((nRet = cfsetispeed(&psd->tty, s)) < 0) ||
			((nRet = cfsetospeed(&psd->tty, s)) < 0))
		{
		    return nRet;
		}

		/////////////////////////////////////////////////////////////////////
		// data bits

		switch(pscp->data)
		{
		case 5:
			psd->tty.c_cflag &= ~CSIZE;
			psd->tty.c_cflag |= CS5; // 5 bits per byte
			break;
		case 6:
			psd->tty.c_cflag &= ~CSIZE;
			psd->tty.c_cflag |= CS6; // 6 bits per byte
			break;
		case 7:
			psd->tty.c_cflag &= ~CSIZE;
			psd->tty.c_cflag |= CS7; // 7 bits per byte
			break;
		case 8:
			psd->tty.c_cflag &= ~CSIZE;
			psd->tty.c_cflag |= CS8; // 8 bits per byte
			break;
		default:
			errno = EINVAL;
		    return -1;
		}

		/////////////////////////////////////////////////////////////////////
		// stop bits

		switch(pscp->stop)
		{
		case 1:
			psd->tty.c_cflag &= ~CSTOPB; // Clear stop field, only one stop bit used in communication
			break;
		case 2:
			psd->tty.c_cflag |= CSTOPB;  // Set stop field, two stop bits used in communication
			break;
		default:
			errno = EINVAL;
		    return -1;
		}

		/////////////////////////////////////////////////////////////////////
		// parity

		switch(toupper(pscp->parity))
		{
		case 'N':
			psd->tty.c_cflag &= ~(PARENB | PARODD);	// Clear parity bit, disabling parity
			break;
		case 'E':
			psd->tty.c_cflag |= PARENB;		// Set parity bit, enabling parity
			psd->tty.c_cflag &= ~PARODD;	// Clear odd parity bit, enabling even parity
			break;
		case 'O':
			psd->tty.c_cflag |= (PARENB | PARODD);	// Set parity bits, enabling odd parity
			break;
		default:
			errno = EINVAL;
		    return -1;
		}

		/////////////////////////////////////////////////////////////////////
		// RTS/CTS flow control
		// If the CRTSCTS field is set, hardware RTS/CTS flow control is enabled. The most common setting here is to disable it.
		// Enabling this when it should be disabled can result in your serial port receiving no data, as the sender will buffer
		// it indefinitely, waiting for you to be “ready”.

		if(pscp->flowHW)
			psd->tty.c_cflag |= CRTSCTS;  // Enable RTS/CTS hardware flow control
		else
			psd->tty.c_cflag &= ~CRTSCTS; // Disable RTS/CTS hardware flow control (most common)

		/////////////////////////////////////////////////////////////////////
		// Setting CLOCAL disables modem-specific signal lines such as carrier detect. It also
		// prevents the controlling process from getting sent a SIGHUP signal when a modem disconnect
		// is detected, which is usually a good thing here. Setting CLOCAL allows us to read data (we definitely want that!).

		psd->tty.c_cflag |= (CREAD | CLOCAL); // Turn on READ & ignore ctrl lines (CLOCAL = 1)

		/////////////////////////////////////////////////////////////////////
		// UNIX systems provide two basic modes of input, canonical and non-canonical mode. In canonical mode, input is
		// processed when a new line character is received. The receiving application receives that data line-by-line.
		// This is usually undesirable when dealing with a serial port, and so we normally want to disable canonical mode.
		// Also, in canonical mode, some characters such as backspace are treated specially, and are used to edit the
		// current line of text (erase). Again, we don’t want this feature if processing raw serial data, as it will
		// cause particular bytes to go missing!

		psd->tty.c_lflag &= ~ICANON;

		/////////////////////////////////////////////////////////////////////
		// Echo
		// If this bit is set, sent characters will be echoed back. Because we disabled canonical mode,
		// I don’t think these bits actually do anything, but it doesn’t harm to disable them just in case!

		psd->tty.c_lflag &= ~ECHO;		// Disable echo
		psd->tty.c_lflag &= ~ECHOE;		// Disable erasure
		psd->tty.c_lflag &= ~ECHONL;	// Disable new-line echo

		/////////////////////////////////////////////////////////////////////
		// Signal chars
		// When the ISIG bit is set, INTR, QUIT and SUSP characters are interpreted.
		// We don’t want this with a serial port, so clear this bit.

		psd->tty.c_lflag &= ~ISIG; // Disable interpretation of INTR, QUIT and SUSP

		/////////////////////////////////////////////////////////////////////
		// Software Flow Control (IXOFF, IXON, IXANY)
		// Clearing IXOFF, IXON and IXANY disables software flow control.

		if(pscp->flowSW)
			psd->tty.c_iflag |= (IXON | IXOFF); // Turn on s/w flow ctrl
		else
			psd->tty.c_iflag &= ~(IXON | IXOFF | IXANY); // Turn off s/w flow ctrl

		/////////////////////////////////////////////////////////////////////
		// Disabling Special Handling Of Bytes On Receive
		// Clearing all of the following bits disables any special handling of the bytes as they
		// are received by the serial port, before they are passed to the application. We just want the raw data!

		psd->tty.c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP | INLCR | IGNCR | ICRNL); // Disable any special handling of received bytes

		/////////////////////////////////////////////////////////////////////
		// When configuring a serial port, we want to disable any special handling of output chars/bytes.

		psd->tty.c_oflag &= ~OPOST; // Prevent special interpretation of output bytes (e.g. newline chars)
		psd->tty.c_oflag &= ~ONLCR; // Prevent conversion of newline to carriage return/line feed

		/////////////////////////////////////////////////////////////////////
		// VMIN and VTIME

		psd->tty.c_cc[VTIME] = psd->tty.c_cc[VMIN] = 0;    // No blocking, return immediately with what is available

		/////////////////////////////////////////////////////////////////////
		// set configuration

		if((nRet = tcsetattr(psd->fd, TCSAFLUSH, &psd->tty)) == 0)
			memcpy(&psd->cfg, pscp, sizeof(GFA_SER_CFG_PARAMS));
		return nRet;
	}

	errno = EINVAL;
    return -1;
}

/////////////////////////////////////////////////////////////////////////////

int GfaSerialSetBaudrate(HGFADEVICE hSer, uint32_t nBaudrate)
{
	if(hSer && GfaSerialIsValidBaudrate(nBaudrate))
	{
		GFA_SER_CFG_PARAMS scp;

		if(GfaSerialGetConfig(hSer, &scp, sizeof(scp)) == sizeof(scp))
		{
			scp.baud = nBaudrate;
			return GfaSerialSetConfig(hSer, &scp, sizeof(scp));
		}
	}

	errno = EINVAL;
    return -1;
}

/////////////////////////////////////////////////////////////////////////////

bool GfaSerialGetDeviceInterface(LPGFA_GENERIC_DEVICE_INTERFACE pDevItf)
{
	if(pDevItf)
	{
		pDevItf->pfnOpen			= (PFN_GFA_GENERIC_DEV_OPEN)GfaSerialOpen;
		pDevItf->pfnClose			= GfaSerialClose;
		pDevItf->pfnGetConfig		= (PFN_GFA_GENERIC_DEV_GET_CONFIG)GfaSerialGetConfig;
		pDevItf->pfnSetConfig		= (PFN_GFA_GENERIC_DEV_SET_CONFIG)GfaSerialSetConfig;
		pDevItf->pfnIsValidBaudrate = GfaSerialIsValidBaudrate;
		pDevItf->pfnSetBaudrate		= GfaSerialSetBaudrate;
		pDevItf->pfnGetTimeouts		= GfaSerialGetTimeouts;
		pDevItf->pfnSetTimeouts		= GfaSerialSetTimeouts;
		pDevItf->pfnPurgeRXBuffer	= GfaSerialPurgeRXBuffer;
		pDevItf->pfnReceive			= GfaSerialReceive;
		pDevItf->pfnRead			= GfaSerialRead;
		pDevItf->pfnPop				= GfaSerialPop;
		pDevItf->pfnPeek			= GfaSerialPeek;
		pDevItf->pfnTransmit		= GfaSerialTransmit;
		pDevItf->pfnWrite			= GfaSerialWrite;
		pDevItf->pfnPush			= GfaSerialPush;
		return true;
	}

	errno = EINVAL;
	return false;
}

/////////////////////////////////////////////////////////////////////////////

bool GfaSerialIsValidBaudrate(uint32_t nBaudrate)
{
	return _MapBaudrate(nBaudrate) != (speed_t)-1;
}

/////////////////////////////////////////////////////////////////////////////

ssize_t GfaSerialPurgeRXBuffer(HGFADEVICE hSer)
{
	struct timeval tvSave;

	if(hSer && GfaSerialGetTimeouts(hSer, &tvSave, NULL))
	{
		uint8_t b[256];
		ssize_t nRet = 0, nRx;
		LPGFA_SERIAL_DEVICE psd = (LPGFA_SERIAL_DEVICE)hSer;
		GfaSerialSetTimeouts(hSer, &psd->tvPurge, NULL);

		while((nRx = GfaSerialReceive(hSer, b, sizeof(b))) > 0)
			nRet += nRx;

		GfaSerialSetTimeouts(hSer, &tvSave, NULL);
		return nRet;
	}

	errno = EINVAL;
    return -1;
}

/////////////////////////////////////////////////////////////////////////////

bool GfaSerialGetTimeouts(HGFADEVICE hSer, struct timeval *ptvRX, struct timeval *ptvTX)
{
	if(hSer && (ptvRX || ptvTX))
	{
		LPGFA_SERIAL_DEVICE psd = (LPGFA_SERIAL_DEVICE)hSer;
		if(ptvRX)
			memcpy(ptvRX, &psd->tvRX, sizeof(struct timeval));
		if(ptvTX)
			memcpy(ptvTX, &psd->tvTX, sizeof(struct timeval));
		return true;
	}

	errno = EINVAL;
    return false;
}

/////////////////////////////////////////////////////////////////////////////

bool GfaSerialSetTimeouts(HGFADEVICE hSer, const struct timeval *ptvRX, const struct timeval *ptvTX)
{
	if(hSer && (ptvRX || ptvTX))
	{
		LPGFA_SERIAL_DEVICE psd = (LPGFA_SERIAL_DEVICE)hSer;
		if(ptvRX)
			memcpy(&psd->tvRX, ptvRX, sizeof(struct timeval));
		if(ptvTX)
			memcpy(&psd->tvTX, ptvTX, sizeof(struct timeval));
		return true;
	}

	errno = EINVAL;
    return false;
}

/////////////////////////////////////////////////////////////////////////////

ssize_t GfaSerialTransmit(HGFADEVICE hSer, const void *pData, size_t nCbToWrite)
{
	if(hSer && pData && nCbToWrite)
	{
		fd_set fds;
		struct timeval tv;
		ssize_t nRet = 0;
		ssize_t nWritten = 0;
		const char *pszData = (const char*)pData;
		LPGFA_SERIAL_DEVICE psd = (LPGFA_SERIAL_DEVICE)hSer;
		_CopyTimeval(&tv, &psd->tvTX);

		while(nWritten < (ssize_t)nCbToWrite)
		{
			FD_ZERO(&fds);
			FD_SET(psd->fd, &fds);

			nRet = select(psd->fd + 1, NULL, &fds, NULL, &tv);

			if(nRet < 0)
				return -1;
			else if(nRet == 0)
			{
				errno = ETIMEDOUT;
				break;
			}

			nRet = write(psd->fd, pszData, nCbToWrite - nWritten);

			if(nRet < 0)
				return -1;
			else if(nRet == 0)
			{
				// should never happen!
				errno = ENODATA;
				return -1;
			}
			else
			{
				if(	psd->cfg.bHandleTxEcho &&
					!_ReadEcho(hSer, pszData, nRet))
				{
					GfaSerialPurgeRXBuffer(hSer);
					errno = ECOMM;
					return -1;
				}

				pszData += nRet;
				nWritten += nRet;
			}
		}

		return nWritten;
	}

	errno = EINVAL;
	return -1;
}

/////////////////////////////////////////////////////////////////////////////

ssize_t GfaSerialWrite(HGFADEVICE hSer, const void *pData, size_t nCbData)
{
	if(hSer && pData && nCbData)
	{
		ssize_t nRet;
		LPGFA_SERIAL_DEVICE psd = (LPGFA_SERIAL_DEVICE)hSer;

		if((nRet = write(psd->fd, pData, nCbData)) > 0)
		{
			if(	psd->cfg.bHandleTxEcho &&
				!_ReadEcho(hSer, pData, nRet))
			{
				GfaSerialPurgeRXBuffer(hSer);
				errno = ECOMM;
				return -1;
			}
		}

		return nRet;
	}

	errno = EINVAL;
	return -1;
}

/////////////////////////////////////////////////////////////////////////////

ssize_t GfaSerialPush(HGFADEVICE hSer, uint8_t b)
{
	if(hSer)
	{
		fd_set fds;
		struct timeval tv;
		ssize_t nRet = 0;
		LPGFA_SERIAL_DEVICE psd = (LPGFA_SERIAL_DEVICE)hSer;
		_CopyTimeval(&tv, &psd->tvTX);

		FD_ZERO(&fds);
		FD_SET(psd->fd, &fds);

		nRet = select(psd->fd + 1, NULL, &fds, NULL, &tv);

		if(nRet < 0)
			return -1;
		else if(nRet == 0)
		{
			errno = ETIMEDOUT;
			return 0;
		}

		if((nRet = write(psd->fd, &b, 1)) == 1)
		{
			if(	psd->cfg.bHandleTxEcho &&
				!_ReadEcho(hSer, &b, 1))
			{
				GfaSerialPurgeRXBuffer(hSer);
				errno = ECOMM;
				return -1;
			}
		}

		return nRet;
	}

	errno = EINVAL;
	return -1;
}

/////////////////////////////////////////////////////////////////////////////

ssize_t GfaSerialReceive(HGFADEVICE hSer, void *pBuf, size_t nCbToRead)
{
	if(hSer && pBuf && nCbToRead)
	{
		fd_set fds;
		struct timeval tv;
		ssize_t nRet = 0;
		ssize_t nRead = 0;
		char *pszBuf = (char*)pBuf;
		LPGFA_SERIAL_DEVICE psd = (LPGFA_SERIAL_DEVICE)hSer;
		_CopyTimeval(&tv, &psd->tvRX);

		while(nRead < (ssize_t)nCbToRead)
		{
			FD_ZERO(&fds);
			FD_SET(psd->fd, &fds);

			nRet = select(psd->fd + 1, &fds, NULL, NULL, &tv);

			if(nRet < 0)
				return -1;
			else if(nRet == 0)
			{
				errno = ETIMEDOUT;
				break;
			}

			nRet = read(psd->fd, pszBuf, nCbToRead - nRead);

			if(nRet < 0)
				return -1;
			else if(nRet == 0)
			{
				// should never happen!
				errno = ENODATA;
				return -1;
			}
			else
			{
				pszBuf += nRet;
				nRead += nRet;
			}
		}

		return nRead;
	}

	errno = EINVAL;
	return -1;
}

/////////////////////////////////////////////////////////////////////////////

ssize_t GfaSerialRead(HGFADEVICE hSer, void *pBuf, size_t nCbToRead)
{
	if(hSer && pBuf && nCbToRead)
	{
		LPGFA_SERIAL_DEVICE psd = (LPGFA_SERIAL_DEVICE)hSer;
		return read(psd->fd, pBuf, nCbToRead);
	}

	errno = EINVAL;
	return -1;
}

/////////////////////////////////////////////////////////////////////////////

ssize_t GfaSerialPop(HGFADEVICE hSer, uint8_t *pb)
{
	if(hSer && pb)
	{
		fd_set fds;
		struct timeval tv;
		ssize_t nRet = 0;
		LPGFA_SERIAL_DEVICE psd = (LPGFA_SERIAL_DEVICE)hSer;

		FD_ZERO(&fds);
		FD_SET(psd->fd, &fds);
		_CopyTimeval(&tv, &psd->tvRX);

		nRet = select(psd->fd + 1, &fds, NULL, NULL, &tv);

		if(nRet < 0)
			return -1;
		else if(nRet == 0)
		{
			errno = ETIMEDOUT;
			return 0;
		}

		return read(psd->fd, pb, 1);
	}

	errno = EINVAL;
	return -1;
}

/////////////////////////////////////////////////////////////////////////////

ssize_t GfaSerialPeek(HGFADEVICE hSer)
{
	if(hSer)
	{
		fd_set fds;
		struct timeval tvNull = {0, 0};
		LPGFA_SERIAL_DEVICE psd = (LPGFA_SERIAL_DEVICE)hSer;

		FD_ZERO(&fds);
		FD_SET(psd->fd, &fds);

		return select(psd->fd + 1, &fds, NULL, NULL, &tvNull);
	}

	errno = EINVAL;
	return -1;
}