n_hdlc.c

powerpc内核mpc8241linux系统下char驱动程序

	if (debuglevel >= DEBUG_LEVEL_INFO)	
		printk("%s(%d)n_hdlc_tty_open() called\n",__FILE__,__LINE__);
		
	/* There should not be an existing table for this slot. */
	if (n_hdlc) {
		printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
		return -EEXIST;
	}
	
	n_hdlc = n_hdlc_alloc();
	if (!n_hdlc) {
		printk (KERN_ERR "n_hdlc_alloc failed\n");
		return -ENFILE;
	}
		
	tty->disc_data = n_hdlc;
	n_hdlc->tty    = tty;
		
	MOD_INC_USE_COUNT;
	
	/* Flush any pending characters in the driver and discipline. */
	
	if (tty->ldisc.flush_buffer)
		tty->ldisc.flush_buffer (tty);

	if (tty->driver.flush_buffer)
		tty->driver.flush_buffer (tty);
		
	if (debuglevel >= DEBUG_LEVEL_INFO)	
		printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
		
	return 0;
	
}	/* end of n_tty_hdlc_open() */

/* n_hdlc_send_frames()
 * 
 * 	send frames on pending send buffer list until the
 * 	driver does not accept a frame (busy)
 * 	this function is called after adding a frame to the
 * 	send buffer list and by the tty wakeup callback
 * 	
 * Arguments:		n_hdlc		pointer to ldisc instance data
 * 			tty		pointer to tty instance data
 * Return Value:	None
 */
static void n_hdlc_send_frames (struct n_hdlc *n_hdlc, struct tty_struct *tty)
{
	register int actual;
	unsigned long flags;
	N_HDLC_BUF *tbuf;
	
	if (debuglevel >= DEBUG_LEVEL_INFO)	
		printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
		
	save_flags(flags);
	cli ();
	if (n_hdlc->tbusy) {
		n_hdlc->woke_up = 1;
		restore_flags(flags);
		return;
	}
	n_hdlc->tbusy = 1;
	restore_flags(flags);

	/* get current transmit buffer or get new transmit */
	/* buffer from list of pending transmit buffers */
		
	tbuf = n_hdlc->tbuf;
	if (!tbuf)
		tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
		
	while (tbuf) {
		if (debuglevel >= DEBUG_LEVEL_INFO)	
			printk("%s(%d)sending frame %p, count=%d\n",
				__FILE__,__LINE__,tbuf,tbuf->count);
			
		/* Send the next block of data to device */
		n_hdlc->woke_up = 0;
		tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
		actual = tty->driver.write(tty, 0, tbuf->buf, tbuf->count);
		    
		/* if transmit error, throw frame away by */
		/* pretending it was accepted by driver */
		if (actual < 0)
			actual = tbuf->count;
		
		if (actual == tbuf->count) {
			if (debuglevel >= DEBUG_LEVEL_INFO)	
				printk("%s(%d)frame %p completed\n",
					__FILE__,__LINE__,tbuf);
					
			/* free current transmit buffer */
			n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,tbuf);
			
			/* this tx buffer is done */
			n_hdlc->tbuf = NULL;
			
			/* wait up sleeping writers */
			wake_up_interruptible(&n_hdlc->write_wait);
	
			/* get next pending transmit buffer */
			tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
		} else {
			if (debuglevel >= DEBUG_LEVEL_INFO)	
				printk("%s(%d)frame %p pending\n",
					__FILE__,__LINE__,tbuf);
					
			/* buffer not accepted by driver */
			
			/* check if wake up code called since last write call */
			if (n_hdlc->woke_up)
				continue;
				
			/* set this buffer as pending buffer */
			n_hdlc->tbuf = tbuf;
			break;
		}
	}
	
	if (!tbuf)
		tty->flags  &= ~(1 << TTY_DO_WRITE_WAKEUP);
	
	/* Clear the re-entry flag */
	save_flags(flags);
	cli ();
	n_hdlc->tbusy = 0;
	restore_flags(flags);
	
	if (debuglevel >= DEBUG_LEVEL_INFO)	
		printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__);
		
}	/* end of n_hdlc_send_frames() */

/* n_hdlc_tty_wakeup()
 *
 *	Callback for transmit wakeup. Called when low level
 *	device driver can accept more send data.
 *
 * Arguments:		tty	pointer to associated tty instance data
 * Return Value:	None
 */
static void n_hdlc_tty_wakeup (struct tty_struct *tty)
{
	struct n_hdlc *n_hdlc = tty2n_hdlc (tty);

	if (debuglevel >= DEBUG_LEVEL_INFO)	
		printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__);
		
	if (!n_hdlc)
		return;

	if (tty != n_hdlc->tty) {
		tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
		return;
	}
	
	if (!n_hdlc->tbuf)
		tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
	else
		n_hdlc_send_frames (n_hdlc, tty);
		
}	/* end of n_hdlc_tty_wakeup() */

/* n_hdlc_tty_room()
 * 
 *	Callback function from tty driver. Return the amount of 
 *	space left in the receiver's buffer to decide if remote
 *	transmitter is to be throttled.
 *
 * Arguments:		tty	pointer to associated tty instance data
 * Return Value:	number of bytes left in receive buffer
 */
static int n_hdlc_tty_room (struct tty_struct *tty)
{
	if (debuglevel >= DEBUG_LEVEL_INFO)	
		printk("%s(%d)n_hdlc_tty_room() called\n",__FILE__,__LINE__);
	/* always return a larger number to prevent */
	/* throttling of remote transmitter. */
	return 65536;
}	/* end of n_hdlc_tty_root() */

/* n_hdlc_tty_receive()
 * 
 * 	Called by tty low level driver when receive data is
 * 	available. Data is interpreted as one HDLC frame.
 * 	
 * Arguments:	 	tty		pointer to tty isntance data
 * 			data		pointer to received data
 * 			flags		pointer to flags for data
 * 			count		count of received data in bytes
 * 	
 * Return Value:	None
 */
static void n_hdlc_tty_receive(struct tty_struct *tty,
	const __u8 * data, char *flags, int count)
{
	register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
	register N_HDLC_BUF *buf;

	if (debuglevel >= DEBUG_LEVEL_INFO)	
		printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
			__FILE__,__LINE__, count);
		
	/* This can happen if stuff comes in on the backup tty */
	if (n_hdlc == 0 || tty != n_hdlc->tty)
		return;
		
	/* verify line is using HDLC discipline */
	if (n_hdlc->magic != HDLC_MAGIC) {
		printk("%s(%d) line not using HDLC discipline\n",
			__FILE__,__LINE__);
		return;
	}
	
	/* get a free HDLC buffer */	
	buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
	if (!buf) {
		/* no buffers in free list, attempt to allocate another rx buffer */
		/* unless the maximum count has been reached */
		if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
			buf = (N_HDLC_BUF*)kmalloc(sizeof(N_HDLC_BUF),GFP_ATOMIC);
	}
	
	if (!buf) {
		printk("%s(%d) no more rx buffers, data discarded\n",
			__FILE__,__LINE__);
		return;
	}
		
	/* copy received data to HDLC buffer */
	memcpy(buf->buf,data,count);
	buf->count=count;

	/* add HDLC buffer to list of received frames */
	n_hdlc_buf_put(&n_hdlc->rx_buf_list,buf);
	
	/* wake up any blocked reads and perform async signalling */
	wake_up_interruptible (&n_hdlc->read_wait);
	if (n_hdlc->tty->fasync != NULL)
		kill_fasync (n_hdlc->tty->fasync, SIGIO);

}	/* end of n_hdlc_tty_receive() */

/* n_hdlc_tty_read()
 * 
 * 	Called to retreive one frame of data (if available)
 * 	
 * Arguments:
 * 
 * 	tty		pointer to tty instance data
 * 	file		pointer to open file object
 * 	buf		pointer to returned data buffer
 * 	nr		size of returned data buffer
 * 	
 * Return Value:
 * 
 * 	Number of bytes returned or error code
 */
static rw_ret_t n_hdlc_tty_read (struct tty_struct *tty,
	struct file *file, __u8 * buf, rw_count_t nr)
{
	struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
	int error;
	rw_ret_t ret;
	N_HDLC_BUF *rbuf;

	if (debuglevel >= DEBUG_LEVEL_INFO)	
		printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
		
	/* Validate the pointers */
	if (!n_hdlc)
		return -EIO;

	/* verify user access to buffer */
	error = verify_area (VERIFY_WRITE, buf, nr);
	if (error != 0) {
		printk(KERN_WARNING"%s(%d) n_hdlc_tty_read() can't verify user "
		"buffer\n",__FILE__,__LINE__);
		return (error);
	}

	for (;;) {
		n_hdlc = tty2n_hdlc (tty);
		if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
			 tty != n_hdlc->tty)
			return 0;

		rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
		if (rbuf)
			break;
			
		/* no data */
		if (file->f_flags & O_NONBLOCK)
			return -EAGAIN;
			
		/* TODO: no timeout? current->timeout = 0;*/
		interruptible_sleep_on (&n_hdlc->read_wait);
		if (signal_pending(current))
			return -EINTR;
	}

	if (rbuf->count > nr) {
		/* frame too large for caller's buffer (discard frame) */
		ret = (rw_ret_t)-EOVERFLOW;
	} else {
		/* Copy the data to the caller's buffer */
		COPY_TO_USER(error,buf,rbuf->buf,rbuf->count);
		if (error)
			ret = (rw_ret_t)error;
		else
			ret = (rw_ret_t)rbuf->count;
	}
	
	/* return HDLC buffer to free list unless the free list */
	/* count has exceeded the default value, in which case the */
	/* buffer is freed back to the OS to conserve memory */
	if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT)
		kfree(rbuf);
	else	
		n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,rbuf);
	
	return ret;
	
}	/* end of n_hdlc_tty_read() */

/* n_hdlc_tty_write()
 * 
 * 	write a single frame of data to device
 * 	
 * Arguments:	tty	pointer to associated tty device instance data
 * 		file	pointer to file object data
 * 		data	pointer to transmit data (one frame)
 * 		count	size of transmit frame in bytes
 * 		
 * Return Value:	number of bytes written (or error code)
 */
static rw_ret_t n_hdlc_tty_write (struct tty_struct *tty, struct file *file,
	const __u8 * data, rw_count_t count)
{
	struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
	int error = 0;
	struct wait_queue wait = {current, NULL};
	N_HDLC_BUF *tbuf;

	if (debuglevel >= DEBUG_LEVEL_INFO)	
		printk("%s(%d)n_hdlc_tty_write() called count=%d\n",
			__FILE__,__LINE__,count);
		
	/* Verify pointers */
	if (!n_hdlc)
		return -EIO;

	if (n_hdlc->magic != HDLC_MAGIC)
		return -EIO;

	/* verify frame size */
	if (count > MAX_HDLC_FRAME_SIZE) {
		if (debuglevel & DEBUG_LEVEL_INFO)
			printk (KERN_WARNING
				"n_hdlc_tty_write: truncating user packet "
				"from %lu to %d\n", (unsigned long) count,
				MAX_HDLC_FRAME_SIZE);
		count = MAX_HDLC_FRAME_SIZE;
	}
	
	/* Allocate transmit buffer */
	tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
	if (!tbuf) {
		/* sleep until transmit buffer available */		
		add_wait_queue(&n_hdlc->write_wait, &wait);
		while (!tbuf) {
			/* TODO: no timeout? current->timeout = 0;*/
			current->state = TASK_INTERRUPTIBLE;
			schedule();

			n_hdlc = tty2n_hdlc (tty);
			if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC || 
			    tty != n_hdlc->tty) {
				printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc);
				error = -EIO;
				break;
			}