1 files changed, 275 insertions, 445 deletions

diff --git a/drivers/tty/n_hdlc.c b/drivers/tty/n_hdlc.c
index 27b506bf03ce..46b09bfb6f3a 100644
--- a/drivers/tty/n_hdlc.c
+++ b/drivers/tty/n_hdlc.c
@@ -18,7 +18,7 @@
  * All HDLC data is frame oriented which means:
  *
  * 1. tty write calls represent one complete transmit frame of data
- *    The device driver should accept the complete frame or none of 
+ *    The device driver should accept the complete frame or none of
  *    the frame (busy) in the write method. Each write call should have
  *    a byte count in the range of 2-65535 bytes (2 is min HDLC frame
  *    with 1 addr byte and 1 ctrl byte). The max byte count of 65535
@@ -39,7 +39,7 @@
  *    tty read calls.
  *
  * 3. tty read calls returns an entire frame of data or nothing.
- *    
+ *
  * 4. all send and receive data is considered raw. No processing
  *    or translation is performed by the line discipline, regardless
  *    of the tty flags
@@ -76,8 +76,6 @@
  * OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#define HDLC_MAGIC 0x239e
-
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
@@ -87,9 +85,6 @@
 #include <linux/interrupt.h>
 #include <linux/ptrace.h>
 
-#undef VERSION
-#define VERSION(major,minor,patch) (((((major)<<8)+(minor))<<8)+(patch))
-
 #include <linux/poll.h>
 #include <linux/in.h>
 #include <linux/ioctl.h>
@@ -101,13 +96,13 @@
 #include <linux/if.h>
 #include <linux/bitops.h>
 
-#include <asm/termios.h>
 #include <linux/uaccess.h>
+#include "tty.h"
 
 /*
  * Buffers for individual HDLC frames
  */
-#define MAX_HDLC_FRAME_SIZE 65535 
+#define MAX_HDLC_FRAME_SIZE 65535
 #define DEFAULT_RX_BUF_COUNT 10
 #define MAX_RX_BUF_COUNT 60
 #define DEFAULT_TX_BUF_COUNT 3
@@ -126,28 +121,22 @@ struct n_hdlc_buf_list {
 
 /**
  * struct n_hdlc - per device instance data structure
- * @magic - magic value for structure
- * @flags - miscellaneous control flags
- * @tty - ptr to TTY structure
- * @backup_tty - TTY to use if tty gets closed
- * @tbusy - reentrancy flag for tx wakeup code
- * @woke_up - FIXME: describe this field
- * @tx_buf_list - list of pending transmit frame buffers
- * @rx_buf_list - list of received frame buffers
- * @tx_free_buf_list - list unused transmit frame buffers
- * @rx_free_buf_list - list unused received frame buffers
+ * @tbusy: reentrancy flag for tx wakeup code
+ * @woke_up: tx wakeup needs to be run again as it was called while @tbusy
+ * @tx_buf_list: list of pending transmit frame buffers
+ * @rx_buf_list: list of received frame buffers
+ * @tx_free_buf_list: list unused transmit frame buffers
+ * @rx_free_buf_list: list unused received frame buffers
  */
 struct n_hdlc {
-	int			magic;
-	__u32			flags;
-	struct tty_struct	*tty;
-	struct tty_struct	*backup_tty;
-	int			tbusy;
-	int			woke_up;
+	bool			tbusy;
+	bool			woke_up;
 	struct n_hdlc_buf_list	tx_buf_list;
 	struct n_hdlc_buf_list	rx_buf_list;
 	struct n_hdlc_buf_list	tx_free_buf_list;
 	struct n_hdlc_buf_list	rx_free_buf_list;
+	struct work_struct	write_work;
+	struct tty_struct	*tty_for_write_work;
 };
 
 /*
@@ -161,39 +150,15 @@ static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
 
 /* Local functions */
 
-static struct n_hdlc *n_hdlc_alloc (void);
-
-/* debug level can be set by insmod for debugging purposes */
-#define DEBUG_LEVEL_INFO	1
-static int debuglevel;
+static struct n_hdlc *n_hdlc_alloc(void);
+static void n_hdlc_tty_write_work(struct work_struct *work);
 
 /* max frame size for memory allocations */
 static int maxframe = 4096;
 
-/* TTY callbacks */
-
-static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
-			   __u8 __user *buf, size_t nr);
-static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
-			    const unsigned char *buf, size_t nr);
-static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
-			    unsigned int cmd, unsigned long arg);
-static __poll_t n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
-				    poll_table *wait);
-static int n_hdlc_tty_open(struct tty_struct *tty);
-static void n_hdlc_tty_close(struct tty_struct *tty);
-static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
-			       char *fp, int count);
-static void n_hdlc_tty_wakeup(struct tty_struct *tty);
-
-#define bset(p,b)	((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
-
-#define tty2n_hdlc(tty)	((struct n_hdlc *) ((tty)->disc_data))
-#define n_hdlc2tty(n_hdlc)	((n_hdlc)->tty)
-
 static void flush_rx_queue(struct tty_struct *tty)
 {
-	struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
+	struct n_hdlc *n_hdlc = tty->disc_data;
 	struct n_hdlc_buf *buf;
 
 	while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list)))
@@ -202,169 +167,95 @@ static void flush_rx_queue(struct tty_struct *tty)
 
 static void flush_tx_queue(struct tty_struct *tty)
 {
-	struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
+	struct n_hdlc *n_hdlc = tty->disc_data;
 	struct n_hdlc_buf *buf;
 
 	while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list)))
 		n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf);
 }
 
-static struct tty_ldisc_ops n_hdlc_ldisc = {
-	.owner		= THIS_MODULE,
-	.magic		= TTY_LDISC_MAGIC,
-	.name		= "hdlc",
-	.open		= n_hdlc_tty_open,
-	.close		= n_hdlc_tty_close,
-	.read		= n_hdlc_tty_read,
-	.write		= n_hdlc_tty_write,
-	.ioctl		= n_hdlc_tty_ioctl,
-	.poll		= n_hdlc_tty_poll,
-	.receive_buf	= n_hdlc_tty_receive,
-	.write_wakeup	= n_hdlc_tty_wakeup,
-	.flush_buffer   = flush_rx_queue,
-};
-
-/**
- * n_hdlc_release - release an n_hdlc per device line discipline info structure
- * @n_hdlc - per device line discipline info structure
- */
-static void n_hdlc_release(struct n_hdlc *n_hdlc)
+static void n_hdlc_free_buf_list(struct n_hdlc_buf_list *list)
 {
-	struct tty_struct *tty = n_hdlc2tty (n_hdlc);
 	struct n_hdlc_buf *buf;
-	
-	if (debuglevel >= DEBUG_LEVEL_INFO)	
-		printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__);
-		
-	/* Ensure that the n_hdlcd process is not hanging on select()/poll() */
-	wake_up_interruptible (&tty->read_wait);
-	wake_up_interruptible (&tty->write_wait);
-
-	if (tty->disc_data == n_hdlc)
-		tty->disc_data = NULL;	/* Break the tty->n_hdlc link */
-
-	/* Release transmit and receive buffers */
-	for(;;) {
-		buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
-		if (buf) {
-			kfree(buf);
-		} else
-			break;
-	}
-	for(;;) {
-		buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
-		if (buf) {
-			kfree(buf);
-		} else
-			break;
-	}
-	for(;;) {
-		buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
-		if (buf) {
-			kfree(buf);
-		} else
-			break;
-	}
-	for(;;) {
-		buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
-		if (buf) {
-			kfree(buf);
-		} else
-			break;
-	}
-	kfree(n_hdlc);
-	
-}	/* end of n_hdlc_release() */
+
+	do {
+		buf = n_hdlc_buf_get(list);
+		kfree(buf);
+	} while (buf);
+}
 
 /**
  * n_hdlc_tty_close - line discipline close
- * @tty - pointer to tty info structure
+ * @tty: pointer to tty info structure
  *
  * Called when the line discipline is changed to something
  * else, the tty is closed, or the tty detects a hangup.
  */
 static void n_hdlc_tty_close(struct tty_struct *tty)
 {
-	struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
-
-	if (debuglevel >= DEBUG_LEVEL_INFO)	
-		printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__);
-		
-	if (n_hdlc != NULL) {
-		if (n_hdlc->magic != HDLC_MAGIC) {
-			printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n");
-			return;
-		}
+	struct n_hdlc *n_hdlc = tty->disc_data;
+
 #if defined(TTY_NO_WRITE_SPLIT)
-		clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
+	clear_bit(TTY_NO_WRITE_SPLIT, &tty->flags);
 #endif
-		tty->disc_data = NULL;
-		if (tty == n_hdlc->backup_tty)
-			n_hdlc->backup_tty = NULL;
-		if (tty != n_hdlc->tty)
-			return;
-		if (n_hdlc->backup_tty) {
-			n_hdlc->tty = n_hdlc->backup_tty;
-		} else {
-			n_hdlc_release (n_hdlc);
-		}
-	}
-	
-	if (debuglevel >= DEBUG_LEVEL_INFO)	
-		printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__);
-		
+	tty->disc_data = NULL;
+
+	/* Ensure that the n_hdlcd process is not hanging on select()/poll() */
+	wake_up_interruptible(&tty->read_wait);
+	wake_up_interruptible(&tty->write_wait);
+
+	cancel_work_sync(&n_hdlc->write_work);
+
+	n_hdlc_free_buf_list(&n_hdlc->rx_free_buf_list);
+	n_hdlc_free_buf_list(&n_hdlc->tx_free_buf_list);
+	n_hdlc_free_buf_list(&n_hdlc->rx_buf_list);
+	n_hdlc_free_buf_list(&n_hdlc->tx_buf_list);
+	kfree(n_hdlc);
 }	/* end of n_hdlc_tty_close() */
 
 /**
  * n_hdlc_tty_open - called when line discipline changed to n_hdlc
- * @tty - pointer to tty info structure
+ * @tty: pointer to tty info structure
  *
  * Returns 0 if success, otherwise error code
  */
-static int n_hdlc_tty_open (struct tty_struct *tty)
+static int n_hdlc_tty_open(struct tty_struct *tty)
 {
-	struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
+	struct n_hdlc *n_hdlc = tty->disc_data;
+
+	pr_debug("%s() called (device=%s)\n", __func__, tty->name);
 
-	if (debuglevel >= DEBUG_LEVEL_INFO)	
-		printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n",
-		__FILE__,__LINE__,
-		tty->name);
-		
 	/* There should not be an existing table for this slot. */
 	if (n_hdlc) {
-		printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
+		pr_err("%s: tty already associated!\n", __func__);
 		return -EEXIST;
 	}
-	
+
 	n_hdlc = n_hdlc_alloc();
 	if (!n_hdlc) {
-		printk (KERN_ERR "n_hdlc_alloc failed\n");
+		pr_err("%s: n_hdlc_alloc failed\n", __func__);
 		return -ENFILE;
 	}
-		
+
+	INIT_WORK(&n_hdlc->write_work, n_hdlc_tty_write_work);
+	n_hdlc->tty_for_write_work = tty;
 	tty->disc_data = n_hdlc;
-	n_hdlc->tty    = tty;
 	tty->receive_room = 65536;
-	
-#if defined(TTY_NO_WRITE_SPLIT)
+
 	/* change tty_io write() to not split large writes into 8K chunks */
-	set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
-#endif
-	
+	set_bit(TTY_NO_WRITE_SPLIT, &tty->flags);
+
 	/* flush receive data from driver */
 	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
- * @n_hdlc - pointer to ldisc instance data
- * @tty - pointer to tty instance data
+ * @n_hdlc: pointer to ldisc instance data
+ * @tty: pointer to tty instance data
  *
  * 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
@@ -376,26 +267,22 @@ static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
 	unsigned long flags;
 	struct n_hdlc_buf *tbuf;
 
-	if (debuglevel >= DEBUG_LEVEL_INFO)	
-		printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
- check_again:
-		
- 	spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
+check_again:
+
+	spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
 	if (n_hdlc->tbusy) {
-		n_hdlc->woke_up = 1;
- 		spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
+		n_hdlc->woke_up = true;
+		spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
 		return;
 	}
-	n_hdlc->tbusy = 1;
-	n_hdlc->woke_up = 0;
+	n_hdlc->tbusy = true;
+	n_hdlc->woke_up = false;
 	spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
 
 	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);
-			
+		pr_debug("sending frame %p, count=%d\n", tbuf, tbuf->count);
+
 		/* Send the next block of data to device */
 		set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 		actual = tty->ops->write(tty, tbuf->buf, tbuf->count);
@@ -409,24 +296,20 @@ static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
 		/* 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);
-					
+			pr_debug("frame %p completed\n", tbuf);
+
 			/* free current transmit buffer */
 			n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
 
 			/* wait up sleeping writers */
 			wake_up_interruptible(&tty->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);
+			pr_debug("frame %p pending\n", tbuf);
 
 			/*
 			 * the buffer was not accepted by driver,
@@ -436,147 +319,124 @@ static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
 			break;
 		}
 	}
-	
+
 	if (!tbuf)
 		clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
-	
+
 	/* Clear the re-entry flag */
 	spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
-	n_hdlc->tbusy = 0;
-	spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); 
-	
-        if (n_hdlc->woke_up)
-	  goto check_again;
-
-	if (debuglevel >= DEBUG_LEVEL_INFO)	
-		printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__);
-		
+	n_hdlc->tbusy = false;
+	spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
+
+	if (n_hdlc->woke_up)
+		goto check_again;
 }	/* end of n_hdlc_send_frames() */
 
 /**
- * n_hdlc_tty_wakeup - Callback for transmit wakeup
- * @tty	- pointer to associated tty instance data
+ * n_hdlc_tty_write_work - Asynchronous callback for transmit wakeup
+ * @work: pointer to work_struct
  *
  * Called when low level device driver can accept more send data.
  */
-static void n_hdlc_tty_wakeup(struct tty_struct *tty)
+static void n_hdlc_tty_write_work(struct work_struct *work)
 {
-	struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
+	struct n_hdlc *n_hdlc = container_of(work, struct n_hdlc, write_work);
+	struct tty_struct *tty = n_hdlc->tty_for_write_work;
 
-	if (debuglevel >= DEBUG_LEVEL_INFO)	
-		printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__);
-		
-	if (!n_hdlc)
-		return;
+	n_hdlc_send_frames(n_hdlc, tty);
+}	/* end of n_hdlc_tty_write_work() */
 
-	if (tty != n_hdlc->tty) {
-		clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
-		return;
-	}
+/**
+ * n_hdlc_tty_wakeup - Callback for transmit wakeup
+ * @tty: pointer to associated tty instance data
+ *
+ * Called when low level device driver can accept more send data.
+ */
+static void n_hdlc_tty_wakeup(struct tty_struct *tty)
+{
+	struct n_hdlc *n_hdlc = tty->disc_data;
 
-	n_hdlc_send_frames (n_hdlc, tty);
-		
+	schedule_work(&n_hdlc->write_work);
 }	/* end of n_hdlc_tty_wakeup() */
 
 /**
  * n_hdlc_tty_receive - Called by tty driver when receive data is available
- * @tty	- pointer to tty instance data
- * @data - pointer to received data
- * @flags - pointer to flags for data
- * @count - count of received data in bytes
+ * @tty: pointer to tty instance data
+ * @data: pointer to received data
+ * @flags: pointer to flags for data
+ * @count: count of received data in bytes
  *
  * Called by tty low level driver when receive data is available. Data is
  * interpreted as one HDLC frame.
  */
 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
-			       char *flags, int count)
+			       const char *flags, int count)
 {
-	register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
+	register struct n_hdlc *n_hdlc = tty->disc_data;
 	register struct 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 || 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;
-	}
-	
-	if ( count>maxframe ) {
-		if (debuglevel >= DEBUG_LEVEL_INFO)	
-			printk("%s(%d) rx count>maxframesize, data discarded\n",
-			       __FILE__,__LINE__);
+	pr_debug("%s() called count=%d\n", __func__, count);
+
+	if (count > maxframe) {
+		pr_debug("rx count>maxframesize, data discarded\n");
 		return;
 	}
 
-	/* get a free HDLC buffer */	
+	/* 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 */
+		/*
+		 * 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 = kmalloc(struct_size(buf, buf, maxframe),
 				      GFP_ATOMIC);
 	}
-	
+
 	if (!buf) {
-		if (debuglevel >= DEBUG_LEVEL_INFO)	
-			printk("%s(%d) no more rx buffers, data discarded\n",
-			       __FILE__,__LINE__);
+		pr_debug("no more rx buffers, data discarded\n");
 		return;
 	}
-		
+
 	/* copy received data to HDLC buffer */
-	memcpy(buf->buf,data,count);
-	buf->count=count;
+	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 (&tty->read_wait);
-	if (n_hdlc->tty->fasync != NULL)
-		kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
+	wake_up_interruptible(&tty->read_wait);
+	if (tty->fasync != NULL)
+		kill_fasync(&tty->fasync, SIGIO, POLL_IN);
 
 }	/* end of n_hdlc_tty_receive() */
 
 /**
  * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
- * @tty - pointer to tty instance data
- * @file - pointer to open file object
- * @buf - pointer to returned data buffer
- * @nr - size of returned data buffer
- * 	
+ * @tty: pointer to tty instance data
+ * @file: pointer to open file object
+ * @kbuf: pointer to returned data buffer
+ * @nr: size of returned data buffer
+ * @cookie: stored rbuf from previous run
+ * @offset: offset into the data buffer
+ *
  * Returns the number of bytes returned or error code.
  */
 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
-			   __u8 __user *buf, size_t nr)
+			   __u8 *kbuf, size_t nr,
+			   void **cookie, unsigned long offset)
 {
-	struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
+	struct n_hdlc *n_hdlc = tty->disc_data;
 	int ret = 0;
 	struct n_hdlc_buf *rbuf;
 	DECLARE_WAITQUEUE(wait, current);
 
-	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 */
-	if (!access_ok(buf, nr)) {
-		printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
-		"buffer\n", __FILE__, __LINE__);
-		return -EFAULT;
-	}
+	/* Is this a repeated call for an rbuf we already found earlier? */
+	rbuf = *cookie;
+	if (rbuf)
+		goto have_rbuf;
 
 	add_wait_queue(&tty->read_wait, &wait);
 
@@ -591,26 +451,9 @@ static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
 		set_current_state(TASK_INTERRUPTIBLE);
 
 		rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
-		if (rbuf) {
-			if (rbuf->count > nr) {
-				/* too large for caller's buffer */
-				ret = -EOVERFLOW;
-			} else {
-				__set_current_state(TASK_RUNNING);
-				if (copy_to_user(buf, rbuf->buf, rbuf->count))
-					ret = -EFAULT;
-				else
-					ret = rbuf->count;
-			}
-
-			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);
+		if (rbuf)
 			break;
-		}
-			
+
 		/* no data */
 		if (tty_io_nonblock(tty, file)) {
 			ret = -EAGAIN;
@@ -628,53 +471,74 @@ static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
 	remove_wait_queue(&tty->read_wait, &wait);
 	__set_current_state(TASK_RUNNING);
 
+	if (!rbuf)
+		return ret;
+	*cookie = rbuf;
+
+have_rbuf:
+	/* Have we used it up entirely? */
+	if (offset >= rbuf->count)
+		goto done_with_rbuf;
+
+	/* More data to go, but can't copy any more? EOVERFLOW */
+	ret = -EOVERFLOW;
+	if (!nr)
+		goto done_with_rbuf;
+
+	/* Copy as much data as possible */
+	ret = rbuf->count - offset;
+	if (ret > nr)
+		ret = nr;
+	memcpy(kbuf, rbuf->buf+offset, ret);
+	offset += ret;
+
+	/* If we still have data left, we leave the rbuf in the cookie */
+	if (offset < rbuf->count)
+		return ret;
+
+done_with_rbuf:
+	*cookie = NULL;
+
+	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
- * @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
- * 		
+ * @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
+ *
  * Returns the number of bytes written (or error code).
  */
 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
 			    const unsigned char *data, size_t count)
 {
-	struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
+	struct n_hdlc *n_hdlc = tty->disc_data;
 	int error = 0;
 	DECLARE_WAITQUEUE(wait, current);
 	struct n_hdlc_buf *tbuf;
 
-	if (debuglevel >= DEBUG_LEVEL_INFO)	
-		printk("%s(%d)n_hdlc_tty_write() called count=%zd\n",
-			__FILE__,__LINE__,count);
-		
-	/* Verify pointers */
-	if (!n_hdlc)
-		return -EIO;
-
-	if (n_hdlc->magic != HDLC_MAGIC)
-		return -EIO;
+	pr_debug("%s() called count=%zd\n", __func__, count);
 
 	/* verify frame size */
-	if (count > maxframe ) {
-		if (debuglevel & DEBUG_LEVEL_INFO)
-			printk (KERN_WARNING
-				"n_hdlc_tty_write: truncating user packet "
-				"from %lu to %d\n", (unsigned long) count,
-				maxframe );
+	if (count > maxframe) {
+		pr_debug("%s: truncating user packet from %zu to %d\n",
+				__func__, count, maxframe);
 		count = maxframe;
 	}
-	
+
 	add_wait_queue(&tty->write_wait, &wait);
 
 	for (;;) {
 		set_current_state(TASK_INTERRUPTIBLE);
-	
+
 		tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
 		if (tbuf)
 			break;
@@ -684,15 +548,7 @@ static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
 			break;
 		}
 		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;
-		}
-			
+
 		if (signal_pending(current)) {
 			error = -EINTR;
 			break;
@@ -702,58 +558,51 @@ static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
 	__set_current_state(TASK_RUNNING);
 	remove_wait_queue(&tty->write_wait, &wait);
 
-	if (!error) {		
+	if (!error) {
 		/* Retrieve the user's buffer */
 		memcpy(tbuf->buf, data, count);
 
 		/* Send the data */
 		tbuf->count = error = count;
-		n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
-		n_hdlc_send_frames(n_hdlc,tty);
+		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.
- * @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)
+ * @tty: pointer to tty instance data
+ * @cmd: IOCTL command code
+ * @arg: argument for IOCTL call (cmd dependent)
  *
  * Returns command dependent result.
  */
-static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
-			    unsigned int cmd, unsigned long arg)
+static int n_hdlc_tty_ioctl(struct tty_struct *tty, unsigned int cmd,
+			    unsigned long arg)
 {
-	struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
+	struct n_hdlc *n_hdlc = tty->disc_data;
 	int error = 0;
 	int count;
 	unsigned long flags;
 	struct n_hdlc_buf *buf = NULL;
 
-	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;
+	pr_debug("%s() called %d\n", __func__, cmd);
 
 	switch (cmd) {
 	case FIONREAD:
 		/* report count of read data available */
 		/* in next available frame (if any) */
-		spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
+		spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock, flags);
 		buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list,
 						struct n_hdlc_buf, list_item);
 		if (buf)
 			count = buf->count;
 		else
 			count = 0;
-		spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
+		spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock, flags);
 		error = put_user(count, (int __user *)arg);
 		break;
 
@@ -761,12 +610,12 @@ static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
 		/* get the pending tx byte count in the driver */
 		count = tty_chars_in_buffer(tty);
 		/* add size of next output frame in queue */
-		spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
+		spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
 		buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list,
 						struct n_hdlc_buf, list_item);
 		if (buf)
 			count += buf->count;
-		spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
+		spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
 		error = put_user(count, (int __user *)arg);
 		break;
 
@@ -776,22 +625,22 @@ static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
 		case TCOFLUSH:
 			flush_tx_queue(tty);
 		}
-		/* fall through - to default */
+		fallthrough;	/* to default */
 
 	default:
-		error = n_tty_ioctl_helper(tty, file, cmd, arg);
+		error = n_tty_ioctl_helper(tty, cmd, arg);
 		break;
 	}
 	return error;
-	
+
 }	/* end of n_hdlc_tty_ioctl() */
 
 /**
  * n_hdlc_tty_poll - TTY callback for poll system call
- * @tty - pointer to tty instance data
- * @filp - pointer to open file object for device
- * @poll_table - wait queue for operations
- * 
+ * @tty: pointer to tty instance data
+ * @filp: pointer to open file object for device
+ * @wait: wait queue for operations
+ *
  * Determine which operations (read/write) will not block and return info
  * to caller.
  * Returns a bit mask containing info on which ops will not block.
@@ -799,33 +648,47 @@ static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
 static __poll_t n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
 				    poll_table *wait)
 {
-	struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
+	struct n_hdlc *n_hdlc = tty->disc_data;
 	__poll_t 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) */
-
-		poll_wait(filp, &tty->read_wait, wait);
-		poll_wait(filp, &tty->write_wait, wait);
-
-		/* set bits for operations that won't block */
-		if (!list_empty(&n_hdlc->rx_buf_list.list))
-			mask |= EPOLLIN | EPOLLRDNORM;	/* readable */
-		if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
-			mask |= EPOLLHUP;
-		if (tty_hung_up_p(filp))
-			mask |= EPOLLHUP;
-		if (!tty_is_writelocked(tty) &&
-				!list_empty(&n_hdlc->tx_free_buf_list.list))
-			mask |= EPOLLOUT | EPOLLWRNORM;	/* writable */
-	}
+	/*
+	 * queue the current process into any wait queue that may awaken in the
+	 * future (read and write)
+	 */
+	poll_wait(filp, &tty->read_wait, wait);
+	poll_wait(filp, &tty->write_wait, wait);
+
+	/* set bits for operations that won't block */
+	if (!list_empty(&n_hdlc->rx_buf_list.list))
+		mask |= EPOLLIN | EPOLLRDNORM;	/* readable */
+	if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
+		mask |= EPOLLHUP;
+	if (tty_hung_up_p(filp))
+		mask |= EPOLLHUP;
+	if (!tty_is_writelocked(tty) &&
+			!list_empty(&n_hdlc->tx_free_buf_list.list))
+		mask |= EPOLLOUT | EPOLLWRNORM;	/* writable */
+
 	return mask;
 }	/* end of n_hdlc_tty_poll() */
 
+static void n_hdlc_alloc_buf(struct n_hdlc_buf_list *list, unsigned int count,
+		const char *name)
+{
+	struct n_hdlc_buf *buf;
+	unsigned int i;
+
+	for (i = 0; i < count; i++) {
+		buf = kmalloc(struct_size(buf, buf, maxframe), GFP_KERNEL);
+		if (!buf) {
+			pr_debug("%s(), kmalloc() failed for %s buffer %u\n",
+					__func__, name, i);
+			return;
+		}
+		n_hdlc_buf_put(list, buf);
+	}
+}
+
 /**
  * n_hdlc_alloc - allocate an n_hdlc instance data structure
  *
@@ -833,8 +696,6 @@ static __poll_t n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
  */
 static struct n_hdlc *n_hdlc_alloc(void)
 {
-	struct n_hdlc_buf *buf;
-	int i;
 	struct n_hdlc *n_hdlc = kzalloc(sizeof(*n_hdlc), GFP_KERNEL);
 
 	if (!n_hdlc)
@@ -850,36 +711,17 @@ static struct n_hdlc *n_hdlc_alloc(void)
 	INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list);
 	INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list);
 
-	/* allocate free rx buffer list */
-	for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
-		buf = kmalloc(struct_size(buf, buf, maxframe), GFP_KERNEL);
-		if (buf)
-			n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
-		else if (debuglevel >= DEBUG_LEVEL_INFO)	
-			printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
-	}
-	
-	/* allocate free tx buffer list */
-	for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
-		buf = kmalloc(struct_size(buf, buf, maxframe), GFP_KERNEL);
-		if (buf)
-			n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
-		else if (debuglevel >= DEBUG_LEVEL_INFO)	
-			printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
-	}
-	
-	/* Initialize the control block */
-	n_hdlc->magic  = HDLC_MAGIC;
-	n_hdlc->flags  = 0;
-	
+	n_hdlc_alloc_buf(&n_hdlc->rx_free_buf_list, DEFAULT_RX_BUF_COUNT, "rx");
+	n_hdlc_alloc_buf(&n_hdlc->tx_free_buf_list, DEFAULT_TX_BUF_COUNT, "tx");
+
 	return n_hdlc;
-	
+
 }	/* end of n_hdlc_alloc() */
 
 /**
  * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list
- * @buf_list - pointer to the buffer list
- * @buf - pointer to the buffer
+ * @buf_list: pointer to the buffer list
+ * @buf: pointer to the buffer
  */
 static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
 						struct n_hdlc_buf *buf)
@@ -896,8 +738,8 @@ static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
 
 /**
  * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
- * @buf_list - pointer to buffer list
- * @buf	- pointer to buffer
+ * @buf_list: pointer to buffer list
+ * @buf: pointer to buffer
  */
 static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list,
 			   struct n_hdlc_buf *buf)
@@ -914,8 +756,8 @@ static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list,
 
 /**
  * n_hdlc_buf_get - remove and return an HDLC buffer from list
- * @buf_list - pointer to HDLC buffer list
- * 
+ * @buf_list: pointer to HDLC buffer list
+ *
  * Remove and return an HDLC buffer from the head of the specified HDLC buffer
  * list.
  * Returns a pointer to HDLC buffer if available, otherwise %NULL.
@@ -938,54 +780,43 @@ static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *buf_list)
 	return buf;
 }	/* end of n_hdlc_buf_get() */
 
-static const char hdlc_banner[] __initconst =
-	KERN_INFO "HDLC line discipline maxframe=%u\n";
-static const char hdlc_register_ok[] __initconst =
-	KERN_INFO "N_HDLC line discipline registered.\n";
-static const char hdlc_register_fail[] __initconst =
-	KERN_ERR "error registering line discipline: %d\n";
+static struct tty_ldisc_ops n_hdlc_ldisc = {
+	.owner		= THIS_MODULE,
+	.num		= N_HDLC,
+	.name		= "hdlc",
+	.open		= n_hdlc_tty_open,
+	.close		= n_hdlc_tty_close,
+	.read		= n_hdlc_tty_read,
+	.write		= n_hdlc_tty_write,
+	.ioctl		= n_hdlc_tty_ioctl,
+	.poll		= n_hdlc_tty_poll,
+	.receive_buf	= n_hdlc_tty_receive,
+	.write_wakeup	= n_hdlc_tty_wakeup,
+	.flush_buffer   = flush_rx_queue,
+};
 
 static int __init n_hdlc_init(void)
 {
 	int status;
 
 	/* range check maxframe arg */
-	if (maxframe < 4096)
-		maxframe = 4096;
-	else if (maxframe > 65535)
-		maxframe = 65535;
-
-	printk(hdlc_banner, maxframe);
+	maxframe = clamp(maxframe, 4096, MAX_HDLC_FRAME_SIZE);
 
-	status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
+	status = tty_register_ldisc(&n_hdlc_ldisc);
 	if (!status)
-		printk(hdlc_register_ok);
+		pr_info("N_HDLC line discipline registered with maxframe=%d\n",
+				maxframe);
 	else
-		printk(hdlc_register_fail, status);
+		pr_err("N_HDLC: error registering line discipline: %d\n",
+				status);
 
 	return status;
-	
-}	/* end of init_module() */
 
-#ifdef CONFIG_SPARC
-#undef __exitdata
-#define __exitdata
-#endif
-
-static const char hdlc_unregister_ok[] __exitdata =
-	KERN_INFO "N_HDLC: line discipline unregistered\n";
-static const char hdlc_unregister_fail[] __exitdata =
-	KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
+}	/* end of init_module() */
 
 static void __exit n_hdlc_exit(void)
 {
-	/* Release tty registration of line discipline */
-	int status = tty_unregister_ldisc(N_HDLC);
-
-	if (status)
-		printk(hdlc_unregister_fail, status);
-	else
-		printk(hdlc_unregister_ok);
+	tty_unregister_ldisc(&n_hdlc_ldisc);
 }
 
 module_init(n_hdlc_init);
@@ -993,6 +824,5 @@ module_exit(n_hdlc_exit);
 
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
-module_param(debuglevel, int, 0);
 module_param(maxframe, int, 0);
 MODULE_ALIAS_LDISC(N_HDLC);