n_hdlc.c

powerpc内核mpc8241linux系统下char驱动程序

			if (signal_pending(current)) {
				error = -EINTR;
				break;
			}
			
			tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
		}
		current->state = TASK_RUNNING;
		remove_wait_queue(&n_hdlc->write_wait, &wait);
	}

	if (!error) {		
		/* Retrieve the user's buffer */
		COPY_FROM_USER (error, tbuf->buf, data, count);
		if (error) {
			/* return tx buffer to free list */
			n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,tbuf);
		} else {
			/* Send the data */
			tbuf->count = error = count;
			n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
			n_hdlc_send_frames(n_hdlc,tty);
		}
	}

	return error;
	
}	/* end of n_hdlc_tty_write() */

/* n_hdlc_tty_ioctl()
 *
 *	Process IOCTL system call for the tty device.
 *
 * Arguments:
 *
 *	tty		pointer to tty instance data
 *	file		pointer to open file object for device
 *	cmd		IOCTL command code
 *	arg		argument for IOCTL call (cmd dependent)
 *
 * Return Value:	Command dependent
 */
static int n_hdlc_tty_ioctl (struct tty_struct *tty, struct file * file,
               unsigned int cmd, unsigned long arg)
{
	struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
	int error = 0;
	
	if (debuglevel >= DEBUG_LEVEL_INFO)	
		printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
			__FILE__,__LINE__,cmd);
		
	/* Verify the status of the device */
	if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC)
		return -EBADF;

	switch (cmd) {
	case FIONREAD:
		{
			/* report count of read data available */
			/* in next available frame (if any) */
			int count;
			unsigned long flags;
			spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
			if (n_hdlc->rx_buf_list.head)
				count = n_hdlc->rx_buf_list.head->count;
			else
				count = 0;
			spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
			PUT_USER (error, count, (int *) arg);
		}
		break;
		
	default:
		error = n_tty_ioctl (tty, file, cmd, arg);
		break;
	}
	return error;
	
}	/* end of n_hdlc_tty_ioctl() */

#if LINUX_VERSION_CODE < VERSION(2,1,23)
/* n_hdlc_tty_select()
 * 
 * 	Device select method. Determine if operation requires
 * 	blocking and if so put appropriate wait queue in select
 * 	table and return 0, otherwise return 1.
 * 	
 * Arguments:
 * 
 * 	tty		pointer to tty device instance data
 * 	inode		pointer to inode for device
 * 	filp		pointer to file object
 * 	sel_type	identified the select type (read/write/exception)
 * 	wait		select table for adding wait queue if appropriate
 * 	
 * Return Value:
 * 
 * 	1 if no need to block on operation
 * 	0 if must block and wait queue added to select table
 */
static int n_hdlc_tty_select (struct tty_struct *tty, struct inode *inode,
		struct file *filp, int sel_type, select_table * wait)
{
	struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
	int result = 1;
	
	if (debuglevel >= DEBUG_LEVEL_INFO)	
		printk("%s(%d)n_hdlc_tty_select() called\n",__FILE__,__LINE__);
		
	/* Verify the status of the device */
	if (!n_hdlc)
		return -EBADF;

	if (n_hdlc->magic != HDLC_MAGIC || tty != n_hdlc->tty)
		return -EBADF;

	switch (sel_type) {
	case SEL_IN:
		if (n_hdlc->rx_buf_list.head)
			break;

	case SEL_EX:	/* Exceptions or read errors */
		/* Is this a pty link and the remote disconnected? */
		if (tty->flags & (1 << TTY_OTHER_CLOSED))
			break;

		/* Is this a local link and the modem disconnected? */
		if (tty_hung_up_p (filp))
			break;

		select_wait (&n_hdlc->read_wait, wait);
		result = 0;
		break;
		
	/* Write mode. A write is allowed if there is no current transmission */
	case SEL_OUT:
		if (!n_hdlc->tx_free_buf_list.head) {
			select_wait (&n_hdlc->write_wait, wait);
			result = 0;
		}
		break;
	}
	return result;
}	/* end of n_hdlc_tty_select() */

#else	/* 2.1.23 or later */

/* n_hdlc_tty_poll()
 * 
 * 	TTY callback for poll system call. Determine which 
 * 	operations (read/write) will not block and return
 * 	info to caller.
 * 	
 * Arguments:
 * 
 * 	tty		pointer to tty instance data
 * 	filp		pointer to open file object for device
 * 	poll_table	wait queue for operations
 * 
 * Return Value:
 * 
 * 	bit mask containing info on which ops will not block
 */
static unsigned int n_hdlc_tty_poll (struct tty_struct *tty,
	 struct file *filp, poll_table * wait)
{
	struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
	unsigned int mask = 0;

	if (debuglevel >= DEBUG_LEVEL_INFO)	
		printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
		
	if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
		/* queue current process into any wait queue that */
		/* may awaken in the future (read and write) */
#if LINUX_VERSION_CODE < VERSION(2,1,89)
		poll_wait(&n_hdlc->read_wait, wait);
		poll_wait(&n_hdlc->write_wait, wait);
#else
		poll_wait(filp, &n_hdlc->read_wait, wait);
		poll_wait(filp, &n_hdlc->write_wait, wait);
#endif
		/* set bits for operations that wont block */
		if(n_hdlc->rx_buf_list.head)
			mask |= POLLIN | POLLRDNORM;	/* readable */
		if(tty->flags & (1 << TTY_OTHER_CLOSED))
			mask |= POLLHUP;
		if(tty_hung_up_p(filp))
			mask |= POLLHUP;
		if(n_hdlc->tx_free_buf_list.head)
			mask |= POLLOUT | POLLWRNORM;	/* writable */
	}
	return mask;
}	/* end of n_hdlc_tty_poll() */

#endif

/* n_hdlc_alloc()
 * 
 * 	Allocate an n_hdlc instance data structure
 *
 * Arguments:		None
 * Return Value:	pointer to structure if success, otherwise 0	
 */
static struct n_hdlc *n_hdlc_alloc (void)
{
	struct n_hdlc	*n_hdlc;
	N_HDLC_BUF	*buf;
	int		i;
	
	n_hdlc = (struct n_hdlc *)kmalloc(sizeof(struct n_hdlc), GFP_KERNEL);
	if (!n_hdlc)
		return 0;

	memset(n_hdlc, 0, sizeof(*n_hdlc));

	n_hdlc_buf_list_init(&n_hdlc->rx_free_buf_list);
	n_hdlc_buf_list_init(&n_hdlc->tx_free_buf_list);
	n_hdlc_buf_list_init(&n_hdlc->rx_buf_list);
	n_hdlc_buf_list_init(&n_hdlc->tx_buf_list);
	
	/* allocate free rx buffer list */
	for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
		buf = (N_HDLC_BUF*)kmalloc(sizeof(N_HDLC_BUF),GFP_KERNEL);
		if (buf)
			n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
	}
	
	/* allocate free rx buffer list */
	for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
		buf = (N_HDLC_BUF*)kmalloc(sizeof(N_HDLC_BUF),GFP_KERNEL);
		if (buf)
			n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
	}
	
	/* Initialize the control block */
	n_hdlc->magic  = HDLC_MAGIC;

	n_hdlc->flags  = 0;
	n_hdlc->read_wait  = NULL;
	n_hdlc->write_wait = NULL;
	
	return n_hdlc;
	
}	/* end of n_hdlc_alloc() */

/* n_hdlc_buf_list_init()
 * 
 * 	initialize specified HDLC buffer list
 * 	
 * Arguments:	 	list	pointer to buffer list
 * Return Value:	None	
 */
void n_hdlc_buf_list_init(N_HDLC_BUF_LIST *list)
{
	memset(list,0,sizeof(N_HDLC_BUF_LIST));
		
}	/* end of n_hdlc_buf_list_init() */

/* n_hdlc_buf_put()
 * 
 * 	add specified HDLC buffer to tail of specified list
 * 	
 * Arguments:
 * 
 * 	list	pointer to buffer list
 * 	buf	pointer to buffer
 * 
 * Return Value:	None	
 */
void n_hdlc_buf_put(N_HDLC_BUF_LIST *list,N_HDLC_BUF *buf)
{
	unsigned long flags;
	spin_lock_irqsave(&list->spinlock,flags);
	
	buf->link=NULL;
	if(list->tail)
		list->tail->link = buf;
	else
		list->head = buf;
	list->tail = buf;
	(list->count)++;
	
	spin_unlock_irqrestore(&list->spinlock,flags);
	
}	/* end of n_hdlc_buf_put() */

/* n_hdlc_buf_get()
 * 
 * 	remove and return an HDLC buffer from the
 * 	head of the specified HDLC buffer list
 * 	
 * Arguments:
 * 
 * 	list	pointer to HDLC buffer list
 * 	
 * Return Value:
 * 
 * 	pointer to HDLC buffer if available, otherwise NULL
 */
N_HDLC_BUF* n_hdlc_buf_get(N_HDLC_BUF_LIST *list)
{
	unsigned long flags;
	N_HDLC_BUF *buf;
	spin_lock_irqsave(&list->spinlock,flags);
	
	buf = list->head;
	if (buf) {
		list->head = buf->link;
		(list->count)--;
	}
	if (!list->head)
		list->tail = NULL;
	
	spin_unlock_irqrestore(&list->spinlock,flags);
	return buf;
	
}	/* end of n_hdlc_buf_get() */

/* init_module()
 *
 *	called when module is loading to register line discipline
 * 	
 * Arguments:		None
 * Return Value:	0 if success, otherwise error code
 */
int init_module(void)
{
	static struct tty_ldisc	n_hdlc_ldisc;
	int    status;

	printk("HDLC line discipline: version %s\n", szVersion);

	/* Register the tty discipline */
	
	memset(&n_hdlc_ldisc, 0, sizeof (n_hdlc_ldisc));
	n_hdlc_ldisc.magic		= TTY_LDISC_MAGIC;
#if LINUX_VERSION_CODE >= VERSION(2,1,28)
	n_hdlc_ldisc.name          	= "hdlc";
#endif
	n_hdlc_ldisc.open		= n_hdlc_tty_open;
	n_hdlc_ldisc.close		= n_hdlc_tty_close;
	n_hdlc_ldisc.read		= n_hdlc_tty_read;
	n_hdlc_ldisc.write		= n_hdlc_tty_write;
	n_hdlc_ldisc.ioctl		= n_hdlc_tty_ioctl;
#if LINUX_VERSION_CODE < VERSION(2,1,23)
	n_hdlc_ldisc.select		= n_hdlc_tty_select;
#else
	n_hdlc_ldisc.poll		= n_hdlc_tty_poll;
#endif
	n_hdlc_ldisc.receive_room	= n_hdlc_tty_room;
	n_hdlc_ldisc.receive_buf	= n_hdlc_tty_receive;
	n_hdlc_ldisc.write_wakeup	= n_hdlc_tty_wakeup;

	status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
	if (!status)
		printk (KERN_INFO"N_HDLC line discipline registered.\n");
	else
		printk (KERN_ERR"error registering line discipline: %d\n",status);

	if (status)
		printk(KERN_INFO"N_HDLC: init failure %d\n", status);
	return (status);
	
}	/* end of init_module() */

/* cleanup_module()
 *
 *	called when module is unloading to unregister line discipline
 * 	
 * Arguments:		None
 * Return Value:	None
 */
void cleanup_module(void)
{
	int status;
	/* Release tty registration of line discipline */
	if ((status = tty_register_ldisc(N_HDLC, NULL)))
		printk("N_HDLC: can't unregister line discipline (err = %d)\n", status);
	else
		printk("N_HDLC: line discipline unregistered\n");
}