如何在kernel空间监听串口？

[sukaru]

我要在kernel内监听串口。我尝试如下的代码 结果返回失败

mm_segment_t oldfs;
oldfs = get_fs();
set_fs(KERNEL_DS);
FD_ZERO(&readset);
FD_SET(fd, &readset);
ret = sys_select(pbl.m_hPBLComPortFd+1, &readset, NULL, NULL, NULL);/*这里返回-9 -EBADF*/
set_fs(oldfs);

返回-9是因为在do_select函数里面执行max_select_fd的时候出错了。

int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
{
	ktime_t expire, *to = NULL;
	struct poll_wqueues table;
	poll_table *wait;
	int retval, i, timed_out = 0;
	unsigned long slack = 0;

	rcu_read_lock();
	retval = max_select_fd(n, fds); /*这里返回-9  -EBADF*/
	rcu_read_unlock();
/*
....
...
*/
}

我调试之后发现出错的地方是下面标出来的地方。

static int max_select_fd(unsigned long n, fd_set_bits *fds)
{
	unsigned long *open_fds;
	unsigned long set;
	int max;
	struct fdtable *fdt;

	/* handle last in-complete long-word first */
	set = ~(~0UL << (n & (__NFDBITS-1)));
	n /= __NFDBITS;
	fdt = files_fdtable(current->files);
	open_fds = fdt->open_fds->fds_bits+n;
	max = 0;
	if (set) {
		set &= BITS(fds, n);
		if (set) {
			if (!(set & ~*open_fds))
				goto get_max;
			return -EBADF;/*这里返回的。*/
		}
	}
	while (n) {
		open_fds--;
		n--;
		set = BITS(fds, n);
		if (!set)
			continue;
		if (set & ~*open_fds)
			return -EBADF;
		if (max)
			continue;
get_max:
		do {
			max++;
			set >>= 1;
		} while (set);
		max += n * __NFDBITS;
	}

	return max;
}

谁知道原因么？还是kernel space不能用sys_select函数？

[sukaru]

没人回答么？