path: root/drv_generic_serial.c

/* $Id: drv_generic_serial.c 728 2007-01-14 11:14:38Z michael $
 * $URL: https://ssl.bulix.org/svn/lcd4linux/branches/0.10.1/drv_generic_serial.c $
 *
 * generic driver helper for serial and usbserial displays
 *
 * Copyright (C) 1999, 2000 Michael Reinelt <reinelt@eunet.at>
 * Copyright (C) 2004 The LCD4Linux Team <lcd4linux-devel@users.sourceforge.net>
 *
 * This file is part of LCD4Linux.
 *
 * LCD4Linux is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * LCD4Linux is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 */

/* 
 *
 * exported fuctions:
 *
 * int drv_generic_serial_open (char *section, char *driver, unsigned int flags)
 *   opens the serial port
 *
 * int drv_generic_serial_poll (char *string, int len)
 *   reads from the serial or USB port
 *   without retry
 *
 * int drv_generic_serial_read (char *string, int len);
 *   reads from the serial or USB port
 *   with retry
 *
 * void drv_generic_serial_write (char *string, int len);
 *   writes to the serial or USB port
 *
 * int drv_generic_serial_close (void);
 *   closes the serial port
 *
 */

#include "config.h"

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <termios.h>
#include <fcntl.h>
#include <time.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/stat.h>

#include "debug.h"
#include "qprintf.h"
#include "cfg.h"
#include "drv_generic_serial.h"


extern int got_signal;

static char *Section;
static char *Driver;
static char *Port;
static speed_t Speed;
static int Device = -1;


#define LOCK "/var/lock/LCK..%s"


/****************************************/
/*** generic serial/USB communication ***/
/****************************************/

static pid_t drv_generic_serial_lock_port(const char *Port)
{
    char lockfile[256];
    char tempfile[256];
    char buffer[16];
    char *port, *p;
    int fd, len, pid;

    if (strncmp(Port, "/dev/", 5) == 0) {
	port = strdup(Port + 5);
    } else {
	port = strdup(Port);
    }

    while ((p = strchr(port, '/')) != NULL) {
	*p = '_';
    }

    qprintf(lockfile, sizeof(lockfile), LOCK, port);
    qprintf(tempfile, sizeof(tempfile), LOCK, "TMP.XXXXXX");

    free(port);

    if ((fd = mkstemp(tempfile)) == -1) {
	error("mkstemp(%s) failed: %s", tempfile, strerror(errno));
	return -1;
    }

    if (fchmod(fd, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH) == -1) {
	error("fchmod(%s) failed: %s", tempfile, strerror(errno));
	close(fd);
	unlink(tempfile);
	return -1;
    }

    snprintf(buffer, sizeof(buffer), "%10d\n", (int) getpid());
    len = strlen(buffer);
    if (write(fd, buffer, len) != len) {
	error("write(%s) failed: %s", tempfile, strerror(errno));
	close(fd);
	unlink(tempfile);
	return -1;
    }
    close(fd);


    while (link(tempfile, lockfile) == -1) {

	if (errno != EEXIST) {
	    error("link(%s, %s) failed: %s", tempfile, lockfile, strerror(errno));
	    unlink(tempfile);
	    return -1;
	}

	if ((fd = open(lockfile, O_RDONLY)) == -1) {
	    if (errno == ENOENT)
		continue;	/* lockfile disappared */
	    error("open(%s) failed: %s", lockfile, strerror(errno));
	    unlink(tempfile);
	    return -1;
	}

	len = read(fd, buffer, sizeof(buffer) - 1);
	if (len < 0) {
	    error("read(%s) failed: %s", lockfile, strerror(errno));
	    unlink(tempfile);
	    return -1;
	}

	buffer[len] = '\0';
	if (sscanf(buffer, "%d", &pid) != 1 || pid == 0) {
	    error("scan(%s) failed.", lockfile);
	    unlink(tempfile);
	    return -1;
	}

	if (pid == getpid()) {
	    error("%s already locked by us. uh-oh...", lockfile);
	    unlink(tempfile);
	    return 0;
	}

	if ((kill(pid, 0) == -1) && errno == ESRCH) {
	    error("removing stale lockfile %s", lockfile);
	    if (unlink(lockfile) == -1 && errno != ENOENT) {
		error("unlink(%s) failed: %s", lockfile, strerror(errno));
		unlink(tempfile);
		return pid;
	    }
	    continue;
	}
	unlink(tempfile);
	return pid;
    }

    unlink(tempfile);
    return 0;
}


static pid_t drv_generic_serial_unlock_port(const char *Port)
{
    char lockfile[256];
    char *port, *p;

    if (strncmp(Port, "/dev/", 5) == 0) {
	port = strdup(Port + 5);
    } else {
	port = strdup(Port);
    }

    while ((p = strchr(port, '/')) != NULL) {
	*p = '_';
    }

    qprintf(lockfile, sizeof(lockfile), LOCK, port);
    unlink(lockfile);
    free(port);

    return 0;
}


int drv_generic_serial_open(const char *section, const char *driver, const unsigned int flags)
{
    int i, fd;
    pid_t pid;
    struct termios portset;

    Section = (char *) section;
    Driver = (char *) driver;

    Port = cfg_get(section, "Port", NULL);
    if (Port == NULL || *Port == '\0') {
	error("%s: no '%s.Port' entry from %s", Driver, section, cfg_source());
	return -1;
    }

    if (cfg_number(section, "Speed", 19200, 1200, 115200, &i) < 0)
	return -1;
    switch (i) {
    case 1200:
	Speed = B1200;
	break;
    case 2400:
	Speed = B2400;
	break;
    case 4800:
	Speed = B4800;
	break;
    case 9600:
	Speed = B9600;
	break;
    case 19200:
	Speed = B19200;
	break;
    case 38400:
	Speed = B38400;
	break;
    case 57600:
	Speed = B57600;
	break;
    case 115200:
	Speed = B115200;
	break;
    default:
	error("%s: unsupported speed '%d' from %s", Driver, i, cfg_source());
	return -1;
    }

    info("%s: using port '%s' at %d baud", Driver, Port, i);

    if ((pid = drv_generic_serial_lock_port(Port)) != 0) {
	if (pid == -1)
	    error("%s: port %s could not be locked", Driver, Port);
	else
	    error("%s: port %s is locked by process %d", Driver, Port, pid);
	return -1;
    }

    fd = open(Port, O_RDWR | O_NOCTTY | O_NDELAY);
    if (fd == -1) {
	error("%s: open(%s) failed: %s", Driver, Port, strerror(errno));
	drv_generic_serial_unlock_port(Port);
	return -1;
    }

    if (tcgetattr(fd, &portset) == -1) {
	error("%s: tcgetattr(%s) failed: %s", Driver, Port, strerror(errno));
	drv_generic_serial_unlock_port(Port);
	return -1;
    }

    cfmakeraw(&portset);
    portset.c_cflag |= flags;
    cfsetispeed(&portset, Speed);
    cfsetospeed(&portset, Speed);
    if (tcsetattr(fd, TCSANOW, &portset) == -1) {
	error("%s: tcsetattr(%s) failed: %s", Driver, Port, strerror(errno));
	drv_generic_serial_unlock_port(Port);
	return -1;
    }

    Device = fd;
    return Device;
}


int drv_generic_serial_poll(char *string, const int len)
{
    int ret;
    if (Device == -1)
	return -1;
    ret = read(Device, string, len);
    if (ret < 0 && errno != EAGAIN) {
	error("%s: read(%s) failed: %s", Driver, Port, strerror(errno));
    }
    return ret;
}


int drv_generic_serial_read(char *string, const int len)
{
    int count, run, ret;

    count = len < 0 ? -len : len;

    for (run = 0; run < 10; run++) {
	ret = drv_generic_serial_poll(string, count);
	if (ret >= 0 || errno != EAGAIN)
	    break;
	info("%s: read(%s): EAGAIN", Driver, Port);
	usleep(1000);
    }

    if (ret > 0 && ret != count && len > 0) {
	error("%s: partial read(%s): len=%d ret=%d", Driver, Port, len, ret);
    }

    return ret;
}


void drv_generic_serial_write(const char *string, const int len)
{
    static int error = 0;
    int run, ret;

    if (Device == -1) {
	error("%s: write to closed port %s failed!", Driver, Port);
	return;
    }

    for (run = 0; run < 10; run++) {
	ret = write(Device, string, len);
	if (ret >= 0 || errno != EAGAIN) {
	    break;
	}
	/* EAGAIN: retry 10 times, emit message after 2nd retry */
	if (run > 0) {
	    info("%s: write(%s): EAGAIN #%d", Driver, Port, run);
	}
	usleep(1000);
    }

    if (ret < 0) {
	error("%s: write(%s) failed: %s", Driver, Port, strerror(errno));
	if (++error > 10) {
	    error("%s: too much errors, giving up", Driver);
	    got_signal = -1;
	}
    } else if (ret != len) {
	error("%s: partial write(%s): len=%d ret=%d", Driver, Port, len, ret);
    } else {
	error = 0;
    }
    return;
}


int drv_generic_serial_close(void)
{
    info("%s: closing port %s", Driver, Port);
    close(Device);
    drv_generic_serial_unlock_port(Port);
    free(Port);
    return 0;
}