[Ftdi-usb-sio-devel] open error after closing the port with excess input data

[Satoru M. <sat...@gm...>]

Hi all,

I'm using FT2232 usb serial device with Linux PC and I have a problem
that I get error on re-opening usb serial port after closing the port
with excess input data from usb serial device.

- connect usb serial device which keeps sending data.
- on Linux PC, open usb serial port and not read any data from the
port. (not call read())
- close the port.
- try to open the port again, but open() returns -1 with errno is EIO(=5).

Once fall in this situation,

- removing and attaching the usb device cannot recover it. (open error again)
- unloading and loading (rmmod and modprobe) ftdi_sio module cannot recover it.
- try to unload usbserial module after unloading ftdi_sio, get following error.

ERROR: Module usbserial is in use

 "rmmod -f" then following error.

ERROR: Removing 'usbserial': Resource temporarily unavailable

- only reboot Linux can recover this situation.

I think it is similar to the case reported by Paul in
"[Ftdi-usb-sio-devel] cannot open port after improper closing" at
2009-02-13 00:13.
I'd like to know how to avoid this situation and recover it without
rebooting Linux.

Could anyone give me advice ?

My environment is:

Linux PC: DELL Inspiron Mini 9 and 10.
kernel: 2.6.28-13 (Ubuntu 9.04 Netbook Remix)
ftdi_sio: v1.4.3

Source code that I used for the test is below.
------
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <termios.h>
#include <signal.h>

struct termios gOldTio;

int my_open(const char *device){
    struct termios newtio;
    int fd;
    tcflag_t baudflag = B57600;

    fd = open(device, O_RDWR | O_NOCTTY);
    if (fd < 0){
        fprintf(stderr,"Unable to open device %s for rw : %i\n", device, errno);
        if((fd = open(device, O_RDONLY | O_NOCTTY)) < 0){
            fprintf(stderr,"Unable to open device %s for read only :
%i\n", device, errno);
            return -1;
        }
    }
    tcgetattr(fd,&gOldTio);

    memset(&newtio, 0, sizeof(newtio));
    newtio.c_cflag = CS8 | CLOCAL | CREAD;
    newtio.c_iflag = IGNPAR | IGNBRK;
    newtio.c_cc [VMIN] = 1; /* Otherwise we go info busy loop */
    cfsetispeed(&newtio, baudflag);
    cfsetospeed(&newtio, baudflag);
    newtio.c_oflag = 0;

    if (tcflush(fd, TCIFLUSH) >= 0 && tcsetattr(fd, TCSANOW, &newtio) >= 0){
        return fd;
    }
    close(fd);
    return -1;
}
int gFd = -1;
void my_shutdown(int val){
    tcflush(gFd,TCIFLUSH);
    tcsetattr(gFd,TCSANOW,&gOldTio);
    close(gFd);
    exit(0);
}

int main(int argc, char **argv){
    char *dev = "/dev/ttyUSB1";

    if(argc == 2){
        dev = argv[1];
    }
    gFd = my_open(dev);
    if(gFd != -1){
        if (signal(SIGTERM,my_shutdown) == SIG_ERR){
        }
        if (signal(SIGINT,my_shutdown) == SIG_ERR){
        }
        while(1){
            char buf[1024];
            //*** read(gFd,buf,sizeof(buf));
        }
        close(gFd);
    }
    return 0;
}
------

Thanks
Satoru