Hey, Guys:
I am doing a project that need to communicate with modem. I searched the
web, found this TI's solution called "gsm0710muxd", you can clone the code
from:
git://git.omapzoom.org/platform/hardware/ti/omap3.git
After compiling and running, everything seems perfect. It create 4 pts
node(/dev/pts/0-4) on ttyS0. However, when I logged on target throught ADB,
and try to echo at+ipr? > /dev/pts/0, a read function error occurs.
gsm0710muxd will create 4 threads(named poll_thread), poll_thread will poll
a device using select(). So, when input echo at+ipr? > /dev/pts/0, select
function will return. Then poll_thread will call read function to get input
from pseudo terminal, and read function returns success. Because poll_thread
is a while(1) loop, it will soon call select again. And select function
returns again. read function will called again. But the second time, read
function returns fail with a EIO signal.
Anyone also faced this problem?
Code:
void* poll_thread(void *vargp)
{
LOGMUX(LOG_DEBUG,"Enter");
Poll_Thread_Arg* poll_thread_arg = (Poll_Thread_Arg*)vargp;
if (poll_thread_arg->fd == -1) {
LOGMUX(LOG_ERR, "Serial port not initialized");
goto terminate;
}
while (1) {
int tmp;
fd_set fdr, fdw;
FD_ZERO(&fdr);
FD_ZERO(&fdw);
FD_SET(poll_thread_arg->fd, &fdr);
if ((tmp = select((1+poll_thread_arg->fd), &fdr, &fdw, NULL, NULL)) > 0) {
LOGMUX(LOG_ERR, "fiddle --- Select returns %d, fd = %d!!!!!", tmp,
poll_thread_arg->fd);
if (FD_ISSET(poll_thread_arg->fd, &fdr)) {
if((*(poll_thread_arg->read_function_ptr))(poll_thread_arg->read_function_arg)
!= 0) {
LOGMUX(LOG_WARNING, "Device read function returned error");
goto terminate;
}
}
} else { //No need to evaluate retval=0 case, since no use of timeout in
select()
switch (errno) {
case EINTR:
LOGMUX(LOG_ERR,"Interrupt signal EINTR caught");
break;
case EAGAIN:
LOGMUX(LOG_ERR,"Interrupt signal EAGAIN caught");
break;
case EBADF:
LOGMUX(LOG_ERR,"Interrupt signal EBADF caught");
break;
case EINVAL:
LOGMUX(LOG_ERR,"Interrupt signal EINVAL caught");
break;
default:
LOGMUX(LOG_ERR,"Unknown interrupt signal caught\n");
}
goto terminate;
}
}
goto terminate;
terminate:
LOGMUX(LOG_ERR, "Device polling thread terminated");
free(poll_thread_arg); //free the memory allocated for the thread args
before exiting thread
return NULL;
}
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