I've tried implementing a nonblocking getchar() using two different methods
1) fcntl(fileno(stdin), F_SETFL, (long)O_NONBLOCK);
2) open("/dev/uart_0, O_RDWR | O_NONBLOCK);
and then use a simple read() on the fd. I would expect to have read() return -1 most times with errno set to EAGAIN. However what I am getting instead is ENOMEM (errno = 12).
I am using a basic NIOS2 on a system with 128kB of memory (implemented in M9K blocks in the EPCS4CE55I8L, no external memory). Did I miss something important either in the SOPC environment or in my BSP settings?
My function is as follows:
/* returns 1 with the character in c if a character was available, 0 otherwise */
int getchar_nonblock(int fd, char *c)
{
int ret;
ret = read(fd, c, 1);
if(ret == -1) {
if(errno == EAGAIN) return 0;
printf("? read returned -1, errno set to %i\r\n", errno);
return 0;
}
return 0;
}
