[PATCH] TTY layer buffering revamp

The API and code have been through various bits of initial review by
serial driver people but they definitely need to live somewhere for a
while so the unconverted drivers can get knocked into shape, existing
drivers that have been updated can be better tuned and bugs whacked out.

This replaces the tty flip buffers with kmalloc objects in rings. In the
normal situation for an IRQ driven serial port at typical speeds the
behaviour is pretty much the same, two buffers end up allocated and the
kernel cycles between them as before.

When there are delays or at high speed we now behave far better as the
buffer pool can grow a bit rather than lose characters. This also means
that we can operate at higher speeds reliably.

For drivers that receive characters in blocks (DMA based, USB and
especially virtualisation) the layer allows a lot of driver specific
code that works around the tty layer with private secondary queues to be
removed. The IBM folks need this sort of layer, the smart serial port
people do, the virtualisers do (because a virtualised tty typically
operates at infinite speed rather than emulating 9600 baud).

Finally many drivers had invalid and unsafe attempts to avoid buffer
overflows by directly invoking tty methods extracted out of the innards
of work queue structs. These are no longer needed and all go away. That
fixes various random hangs with serial ports on overflow.

The other change in here is to optimise the receive_room path that is
used by some callers. It turns out that only one ldisc uses receive room
except asa constant and it updates it far far less than the value is
read. We thus make it a variable not a function call.

I expect the code to contain bugs due to the size alone but I'll be
watching and squashing them and feeding out new patches as it goes.

Because the buffers now dynamically expand you should only run out of
buffering when the kernel runs out of memory for real.  That means a lot of
the horrible hacks high performance drivers used to do just aren't needed any
more.

Description:

tty_insert_flip_char is an old API and continues to work as before, as does
tty_flip_buffer_push() [this is why many drivers dont need modification].  It
does now also return the number of chars inserted

There are also

tty_buffer_request_room(tty, len)

which asks for a buffer block of the length requested and returns the space
found.  This improves efficiency with hardware that knows how much to
transfer.

and tty_insert_flip_string_flags(tty, str, flags, len)

to insert a string of characters and flags

For a smart interface the usual code is

    len = tty_request_buffer_room(tty, amount_hardware_says);
    tty_insert_flip_string(tty, buffer_from_card, len);

More description!

At the moment tty buffers are attached directly to the tty.  This is causing a
lot of the problems related to tty layer locking, also problems at high speed
and also with bursty data (such as occurs in virtualised environments)

I'm working on ripping out the flip buffers and replacing them with a pool of
dynamically allocated buffers.  This allows both for old style "byte I/O"
devices and also helps virtualisation and smart devices where large blocks of
data suddenely materialise and need storing.

So far so good.  Lots of drivers reference tty->flip.*.  Several of them also
call directly and unsafely into function pointers it provides.  This will all
break.  Most drivers can use tty_insert_flip_char which can be kept as an API
but others need more.

At the moment I've added the following interfaces, if people think more will
be needed now is a good time to say

 int tty_buffer_request_room(tty, size)

Try and ensure at least size bytes are available, returns actual room (may be
zero).  At the moment it just uses the flipbuf space but that will change.
Repeated calls without characters being added are not cumulative.  (ie if you
call it with 1, 1, 1, and then 4 you'll have four characters of space.  The
other functions will also try and grow buffers in future but this will be a
more efficient way when you know block sizes.

 int tty_insert_flip_char(tty, ch, flag)

As before insert a character if there is room.  Now returns 1 for success, 0
for failure.

 int tty_insert_flip_string(tty, str, len)

Insert a block of non error characters.  Returns the number inserted.

 int tty_prepare_flip_string(tty, strptr, len)

Adjust the buffer to allow len characters to be added.  Returns a buffer
pointer in strptr and the length available.  This allows for hardware that
needs to use functions like insl or mencpy_fromio.

Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Paul Fulghum <paulkf@microgate.com>
Signed-off-by: Hirokazu Takata <takata@linux-m32r.org>
Signed-off-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: John Hawkes <hawkes@sgi.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

30 files changed, 171 insertions, 470 deletions

diff --git a/drivers/serial/21285.c b/drivers/serial/21285.c
index b5cf39468d1..221999bcf8f 100644
--- a/drivers/serial/21285.c
+++ b/drivers/serial/21285.c
@@ -94,15 +94,6 @@ static irqreturn_t serial21285_rx_chars(int irq, void *dev_id, struct pt_regs *r
 
 	status = *CSR_UARTFLG;
 	while (!(status & 0x10) && max_count--) {
-		if (tty->flip.count >= TTY_FLIPBUF_SIZE) {
-			if (tty->low_latency)
-				tty_flip_buffer_push(tty);
-			/*
-			 * If this failed then we will throw away the
-			 * bytes but must do so to clear interrupts
-			 */
-		}
-
 		ch = *CSR_UARTDR;
 		flag = TTY_NORMAL;
 		port->icount.rx++;
diff --git a/drivers/serial/68328serial.c b/drivers/serial/68328serial.c
index 67e9afa000c..4dd5c3f9816 100644
--- a/drivers/serial/68328serial.c
+++ b/drivers/serial/68328serial.c
@@ -294,7 +294,7 @@ static _INLINE_ void receive_chars(struct m68k_serial *info, struct pt_regs *reg
 {
 	struct tty_struct *tty = info->tty;
 	m68328_uart *uart = &uart_addr[info->line];
-	unsigned char ch;
+	unsigned char ch, flag;
 
 	/*
 	 * This do { } while() loop will get ALL chars out of Rx FIFO 
@@ -332,26 +332,24 @@ static _INLINE_ void receive_chars(struct m68k_serial *info, struct pt_regs *reg
 		/*
 		 * Make sure that we do not overflow the buffer
 		 */
-		if (tty->flip.count >= TTY_FLIPBUF_SIZE) {
+		if (tty_request_buffer_room(tty, 1) == 0) {
 			schedule_work(&tty->flip.work);
 			return;
 		}
 
+		flag = TTY_NORMAL;
+
 		if(rx & URX_PARITY_ERROR) {
-			*tty->flip.flag_buf_ptr++ = TTY_PARITY;
+			flag = TTY_PARITY;
 			status_handle(info, rx);
 		} else if(rx & URX_OVRUN) {
-			*tty->flip.flag_buf_ptr++ = TTY_OVERRUN;
+			flag = TTY_OVERRUN;
 			status_handle(info, rx);
 		} else if(rx & URX_FRAME_ERROR) {
-			*tty->flip.flag_buf_ptr++ = TTY_FRAME;
+			flag = TTY_FRAME;
 			status_handle(info, rx);
-		} else {
-			*tty->flip.flag_buf_ptr++ = 0; /* XXX */
 		}
-                *tty->flip.char_buf_ptr++ = ch;
-		tty->flip.count++;
-
+		tty_insert_flip_char(tty, ch, flag);
 #ifndef CONFIG_XCOPILOT_BUGS
 	} while((rx = uart->urx.w) & URX_DATA_READY);
 #endif
diff --git a/drivers/serial/68360serial.c b/drivers/serial/68360serial.c
index 170c9d2a749..60f5a5dc17f 100644
--- a/drivers/serial/68360serial.c
+++ b/drivers/serial/68360serial.c
@@ -394,7 +394,7 @@ static void rs_360_start(struct tty_struct *tty)
 static _INLINE_ void receive_chars(ser_info_t *info)
 {
 	struct tty_struct *tty = info->tty;
-	unsigned char ch, *cp;
+	unsigned char ch, flag, *cp;
 	/*int	ignored = 0;*/
 	int	i;
 	ushort	status;
@@ -438,24 +438,15 @@ static _INLINE_ void receive_chars(ser_info_t *info)
 		cp = (char *)bdp->buf;
 		status = bdp->status;
 
-		/* Check to see if there is room in the tty buffer for
-		 * the characters in our BD buffer.  If not, we exit
-		 * now, leaving the BD with the characters.  We'll pick
-		 * them up again on the next receive interrupt (which could
-		 * be a timeout).
-		 */
-		if ((tty->flip.count + i) >= TTY_FLIPBUF_SIZE)
-			break;
-
 		while (i-- > 0) {
 			ch = *cp++;
-			*tty->flip.char_buf_ptr = ch;
 			icount->rx++;
 
 #ifdef SERIAL_DEBUG_INTR
 			printk("DR%02x:%02x...", ch, status);
 #endif
-			*tty->flip.flag_buf_ptr = 0;
+			flag = TTY_NORMAL;
+
 			if (status & (BD_SC_BR | BD_SC_FR |
 				       BD_SC_PR | BD_SC_OV)) {
 				/*
@@ -490,30 +481,18 @@ static _INLINE_ void receive_chars(ser_info_t *info)
 					if (info->flags & ASYNC_SAK)
 						do_SAK(tty);
 				} else if (status & BD_SC_PR)
-					*tty->flip.flag_buf_ptr = TTY_PARITY;
+					flag = TTY_PARITY;
 				else if (status & BD_SC_FR)
-					*tty->flip.flag_buf_ptr = TTY_FRAME;
-				if (status & BD_SC_OV) {
-					/*
-					 * Overrun is special, since it's
-					 * reported immediately, and doesn't
-					 * affect the current character
-					 */
-					if (tty->flip.count < TTY_FLIPBUF_SIZE) {
-						tty->flip.count++;
-						tty->flip.flag_buf_ptr++;
-						tty->flip.char_buf_ptr++;
-						*tty->flip.flag_buf_ptr =
-								TTY_OVERRUN;
-					}
-				}
+					flag = TTY_FRAME;
 			}
-			if (tty->flip.count >= TTY_FLIPBUF_SIZE)
-				break;
-
-			tty->flip.flag_buf_ptr++;
-			tty->flip.char_buf_ptr++;
-			tty->flip.count++;
+			tty_insert_flip_char(tty, ch, flag);
+			if (status & BD_SC_OV)
+				/*
+				 * Overrun is special, since it's
+				 * reported immediately, and doesn't
+				 * affect the current character
+				 */
+				tty_insert_flip_char(tty, 0, TTY_OVERRUN);
 		}
 
 		/* This BD is ready to be used again.  Clear status.
@@ -541,12 +520,7 @@ static _INLINE_ void receive_break(ser_info_t *info)
 	/* Check to see if there is room in the tty buffer for
 	 * the break.  If not, we exit now, losing the break.  FIXME
 	 */
-	if ((tty->flip.count + 1) >= TTY_FLIPBUF_SIZE)
-		return;
-	*(tty->flip.flag_buf_ptr++) = TTY_BREAK;
-	*(tty->flip.char_buf_ptr++) = 0;
-	tty->flip.count++;
-
+	tty_insert_flip_char(tty, 0, TTY_BREAK);
 	schedule_work(&tty->flip.work);
 }
 
diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index e8454611cb6..54e5cc0dd5f 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -1142,19 +1142,6 @@ receive_chars(struct uart_8250_port *up, int *status, struct pt_regs *regs)
 	char flag;
 
 	do {
-		/* The following is not allowed by the tty layer and
-		   unsafe. It should be fixed ASAP */
-		if (unlikely(tty->flip.count >= TTY_FLIPBUF_SIZE)) {
-			if (tty->low_latency) {
-				spin_unlock(&up->port.lock);
-				tty_flip_buffer_push(tty);
-				spin_lock(&up->port.lock);
-			}
-			/*
-			 * If this failed then we will throw away the
-			 * bytes but must do so to clear interrupts
-			 */
-		}
 		ch = serial_inp(up, UART_RX);
 		flag = TTY_NORMAL;
 		up->port.icount.rx++;
diff --git a/drivers/serial/amba-pl010.c b/drivers/serial/amba-pl010.c
index 48f6e872314..3490022e9fd 100644
--- a/drivers/serial/amba-pl010.c
+++ b/drivers/serial/amba-pl010.c
@@ -154,15 +154,6 @@ pl010_rx_chars(struct uart_port *port)
 
 	status = UART_GET_FR(port);
 	while (UART_RX_DATA(status) && max_count--) {
-		if (tty->flip.count >= TTY_FLIPBUF_SIZE) {
-			if (tty->low_latency)
-				tty_flip_buffer_push(tty);
-			/*
-			 * If this failed then we will throw away the
-			 * bytes but must do so to clear interrupts.
-			 */
-		}
-
 		ch = UART_GET_CHAR(port);
 		flag = TTY_NORMAL;
 
diff --git a/drivers/serial/amba-pl011.c b/drivers/serial/amba-pl011.c
index 12967055616..034a029e356 100644
--- a/drivers/serial/amba-pl011.c
+++ b/drivers/serial/amba-pl011.c
@@ -120,15 +120,6 @@ pl011_rx_chars(struct uart_amba_port *uap)
 
 	status = readw(uap->port.membase + UART01x_FR);
 	while ((status & UART01x_FR_RXFE) == 0 && max_count--) {
-		if (tty->flip.count >= TTY_FLIPBUF_SIZE) {
-			if (tty->low_latency)
-				tty_flip_buffer_push(tty);
-			/*
-			 * If this failed then we will throw away the
-			 * bytes but must do so to clear interrupts
-			 */
-		}
-
 		ch = readw(uap->port.membase + UART01x_DR) | UART_DUMMY_DR_RX;
 		flag = TTY_NORMAL;
 		uap->port.icount.rx++;
diff --git a/drivers/serial/au1x00_uart.c b/drivers/serial/au1x00_uart.c
index a274ebf256a..ceb5d7f37bb 100644
--- a/drivers/serial/au1x00_uart.c
+++ b/drivers/serial/au1x00_uart.c
@@ -241,18 +241,12 @@ static _INLINE_ void
 receive_chars(struct uart_8250_port *up, int *status, struct pt_regs *regs)
 {
 	struct tty_struct *tty = up->port.info->tty;
-	unsigned char ch;
+	unsigned char ch, flag;
 	int max_count = 256;
 
 	do {
-		if (unlikely(tty->flip.count >= TTY_FLIPBUF_SIZE)) {
-			tty->flip.work.func((void *)tty);
-			if (tty->flip.count >= TTY_FLIPBUF_SIZE)
-				return; // if TTY_DONT_FLIP is set
-		}
 		ch = serial_inp(up, UART_RX);
-		*tty->flip.char_buf_ptr = ch;
-		*tty->flip.flag_buf_ptr = TTY_NORMAL;
+		flag = TTY_NORMAL;
 		up->port.icount.rx++;
 
 		if (unlikely(*status & (UART_LSR_BI | UART_LSR_PE |
@@ -292,30 +286,23 @@ receive_chars(struct uart_8250_port *up, int *status, struct pt_regs *regs)
 #endif
 			if (*status & UART_LSR_BI) {
 				DEBUG_INTR("handling break....");
-				*tty->flip.flag_buf_ptr = TTY_BREAK;
+				flag = TTY_BREAK;
 			} else if (*status & UART_LSR_PE)
-				*tty->flip.flag_buf_ptr = TTY_PARITY;
+				flag = TTY_PARITY;
 			else if (*status & UART_LSR_FE)
-				*tty->flip.flag_buf_ptr = TTY_FRAME;
+				flag = TTY_FRAME;
 		}
 		if (uart_handle_sysrq_char(&up->port, ch, regs))
 			goto ignore_char;
-		if ((*status & up->port.ignore_status_mask) == 0) {
-			tty->flip.flag_buf_ptr++;
-			tty->flip.char_buf_ptr++;
-			tty->flip.count++;
-		}
-		if ((*status & UART_LSR_OE) &&
-		    tty->flip.count < TTY_FLIPBUF_SIZE) {
+		if ((*status & up->port.ignore_status_mask) == 0)
+			tty_insert_flip_char(tty, ch, flag);
+		if (*status & UART_LSR_OE)
 			/*
 			 * Overrun is special, since it's reported
 			 * immediately, and doesn't affect the current
 			 * character.
 			 */
-			*tty->flip.flag_buf_ptr = TTY_OVERRUN;
-			tty->flip.flag_buf_ptr++;
-			tty->flip.char_buf_ptr++;
-			tty->flip.count++;
+			tty_insert_flip_char(tty, 0, TTY_OVERRUN);
 		}
 	ignore_char:
 		*status = serial_inp(up, UART_LSR);
diff --git a/drivers/serial/clps711x.c b/drivers/serial/clps711x.c
index 87ef368384f..8ef999481f9 100644
--- a/drivers/serial/clps711x.c
+++ b/drivers/serial/clps711x.c
@@ -104,8 +104,6 @@ static irqreturn_t clps711xuart_int_rx(int irq, void *dev_id, struct pt_regs *re
 	while (!(status & SYSFLG_URXFE)) {
 		ch = clps_readl(UARTDR(port));
 
-		if (tty->flip.count >= TTY_FLIPBUF_SIZE)
-			goto ignore_char;
 		port->icount.rx++;
 
 		flg = TTY_NORMAL;
diff --git a/drivers/serial/dz.c b/drivers/serial/dz.c
index 4d8516d1bb7..a64ba26a94e 100644
--- a/drivers/serial/dz.c
+++ b/drivers/serial/dz.c
@@ -216,8 +216,6 @@ static inline void dz_receive_chars(struct dz_port *dport)
 
 		if (!tty)
 			break;
-		if (tty->flip.count >= TTY_FLIPBUF_SIZE)
-			break;
 
 		icount->rx++;
 
diff --git a/drivers/serial/icom.c b/drivers/serial/icom.c
index eb31125c6a3..144a7a352b2 100644
--- a/drivers/serial/icom.c
+++ b/drivers/serial/icom.c
@@ -729,19 +729,20 @@ static void recv_interrupt(u16 port_int_reg, struct icom_port *icom_port)
 	unsigned short int status;
 	struct uart_icount *icount;
 	unsigned long offset;
+	unsigned char flag;
 
 	trace(icom_port, "RCV_COMPLETE", 0);
 	rcv_buff = icom_port->next_rcv;
 
 	status = cpu_to_le16(icom_port->statStg->rcv[rcv_buff].flags);
 	while (status & SA_FL_RCV_DONE) {
+		int first = -1;
 
 		trace(icom_port, "FID_STATUS", status);
 		count = cpu_to_le16(icom_port->statStg->rcv[rcv_buff].leLength);
 
+                count = tty_buffer_request_room(tty, count);
 		trace(icom_port, "RCV_COUNT", count);
-		if (count > (TTY_FLIPBUF_SIZE - tty->flip.count))
-			count = TTY_FLIPBUF_SIZE - tty->flip.count;
 
 		trace(icom_port, "REAL_COUNT", count);
 
@@ -749,15 +750,10 @@ static void recv_interrupt(u16 port_int_reg, struct icom_port *icom_port)
 			cpu_to_le32(icom_port->statStg->rcv[rcv_buff].leBuffer) -
 			icom_port->recv_buf_pci;
 
-		memcpy(tty->flip.char_buf_ptr,(unsigned char *)
-		       ((unsigned long)icom_port->recv_buf + offset), count);
-
+		/* Block copy all but the last byte as this may have status */
 		if (count > 0) {
-			tty->flip.count += count - 1;
-			tty->flip.char_buf_ptr += count - 1;
-
-			memset(tty->flip.flag_buf_ptr, 0, count);
-			tty->flip.flag_buf_ptr += count - 1;
+			first = icom_port->recv_buf[offset];
+			tty_insert_flip_string(tty, icom_port->recv_buf + offset, count - 1);
 		}
 
 		icount = &icom_port->uart_port.icount;
@@ -765,12 +761,14 @@ static void recv_interrupt(u16 port_int_reg, struct icom_port *icom_port)
 
 		/* Break detect logic */
 		if ((status & SA_FLAGS_FRAME_ERROR)
-		    && (tty->flip.char_buf_ptr[0] == 0x00)) {
+		    && first == 0) {
 			status &= ~SA_FLAGS_FRAME_ERROR;
 			status |= SA_FLAGS_BREAK_DET;
 			trace(icom_port, "BREAK_DET", 0);
 		}
 
+		flag = TTY_NORMAL;
+
 		if (status &
 		    (SA_FLAGS_BREAK_DET | SA_FLAGS_PARITY_ERROR |
 		     SA_FLAGS_FRAME_ERROR | SA_FLAGS_OVERRUN)) {
@@ -797,33 +795,26 @@ static void recv_interrupt(u16 port_int_reg, struct icom_port *icom_port)
 			status &= icom_port->read_status_mask;
 
 			if (status & SA_FLAGS_BREAK_DET) {
-				*tty->flip.flag_buf_ptr = TTY_BREAK;
+				flag = TTY_BREAK;
 			} else if (status & SA_FLAGS_PARITY_ERROR) {
 				trace(icom_port, "PARITY_ERROR", 0);
-				*tty->flip.flag_buf_ptr = TTY_PARITY;
+				flag = TTY_PARITY;
 			} else if (status & SA_FLAGS_FRAME_ERROR)
-				*tty->flip.flag_buf_ptr = TTY_FRAME;
-
-			if (status & SA_FLAGS_OVERRUN) {
-				/*
-				 * Overrun is special, since it's
-				 * reported immediately, and doesn't
-				 * affect the current character
-				 */
-				if (tty->flip.count < TTY_FLIPBUF_SIZE) {
-					tty->flip.count++;
-					tty->flip.flag_buf_ptr++;
-					tty->flip.char_buf_ptr++;
-					*tty->flip.flag_buf_ptr = TTY_OVERRUN;
-				}
-			}
+				flag = TTY_FRAME;
+
 		}
 
-		tty->flip.flag_buf_ptr++;
-		tty->flip.char_buf_ptr++;
-		tty->flip.count++;
-		ignore_char:
-			icom_port->statStg->rcv[rcv_buff].flags = 0;
+		tty_insert_flip_char(tty, *(icom_port->recv_buf + offset + count - 1), flag);
+
+		if (status & SA_FLAGS_OVERRUN)
+			/*
+			 * Overrun is special, since it's
+			 * reported immediately, and doesn't
+			 * affect the current character
+			 */
+			tty_insert_flip_char(tty, 0, TTY_OVERRUN);
+ignore_char:
+		icom_port->statStg->rcv[rcv_buff].flags = 0;
 		icom_port->statStg->rcv[rcv_buff].leLength = 0;
 		icom_port->statStg->rcv[rcv_buff].WorkingLength =
 			(unsigned short int) cpu_to_le16(RCV_BUFF_SZ);
diff --git a/drivers/serial/imx.c b/drivers/serial/imx.c
index 83c4c121658..5c098be9346 100644
--- a/drivers/serial/imx.c
+++ b/drivers/serial/imx.c
@@ -256,9 +256,6 @@ static irqreturn_t imx_rxint(int irq, void *dev_id, struct pt_regs *regs)
 	error_return:
 		tty_insert_flip_char(tty, rx, flg);
 
-		if (tty->flip.count >= TTY_FLIPBUF_SIZE)
-			goto out;
-
 	ignore_char:
 		rx = URXD0((u32)sport->port.membase);
 	} while(rx & URXD_CHARRDY);
diff --git a/drivers/serial/ioc4_serial.c b/drivers/serial/ioc4_serial.c
index 771676abee6..1d85533d46d 100644
--- a/drivers/serial/ioc4_serial.c
+++ b/drivers/serial/ioc4_serial.c
@@ -2327,19 +2327,13 @@ static void receive_chars(struct uart_port *the_port)
 	spin_lock_irqsave(&the_port->lock, pflags);
 	tty = info->tty;
 
-	if (request_count > TTY_FLIPBUF_SIZE - tty->flip.count)
-		request_count = TTY_FLIPBUF_SIZE - tty->flip.count;
+	request_count = tty_buffer_request_room(tty, IOC4_MAX_CHARS - 2);
 
 	if (request_count > 0) {
 		icount = &the_port->icount;
 		read_count = do_read(the_port, ch, request_count);
 		if (read_count > 0) {
-			flip = 1;
-			memcpy(tty->flip.char_buf_ptr, ch, read_count);
-			memset(tty->flip.flag_buf_ptr, TTY_NORMAL, read_count);
-			tty->flip.char_buf_ptr += read_count;
-			tty->flip.flag_buf_ptr += read_count;
-			tty->flip.count += read_count;
+			tty_insert_flip_string(tty, ch, read_count);
 			icount->rx += read_count;
 		}
 	}
diff --git a/drivers/serial/ip22zilog.c b/drivers/serial/ip22zilog.c
index ef132349f31..66f117d1506 100644
--- a/drivers/serial/ip22zilog.c
+++ b/drivers/serial/ip22zilog.c
@@ -259,13 +259,7 @@ static void ip22zilog_receive_chars(struct uart_ip22zilog_port *up,
 	struct tty_struct *tty = up->port.info->tty;	/* XXX info==NULL? */
 
 	while (1) {
-		unsigned char ch, r1;
-
-		if (unlikely(tty->flip.count >= TTY_FLIPBUF_SIZE)) {
-			tty->flip.work.func((void *)tty);
-			if (tty->flip.count >= TTY_FLIPBUF_SIZE)
-				return;		/* XXX Ignores SysRq when we need it most. Fix. */
-		}
+		unsigned char ch, r1, flag;
 
 		r1 = read_zsreg(channel, R1);
 		if (r1 & (PAR_ERR | Rx_OVR | CRC_ERR)) {
@@ -303,8 +297,7 @@ static void ip22zilog_receive_chars(struct uart_ip22zilog_port *up,
 		}
 
 		/* A real serial line, record the character and status.  */
-		*tty->flip.char_buf_ptr = ch;
-		*tty->flip.flag_buf_ptr = TTY_NORMAL;
+		flag = TTY_NORMAL;
 		up->port.icount.rx++;
 		if (r1 & (BRK_ABRT | PAR_ERR | Rx_OVR | CRC_ERR)) {
 			if (r1 & BRK_ABRT) {
@@ -321,28 +314,21 @@ static void ip22zilog_receive_chars(struct uart_ip22zilog_port *up,
 				up->port.icount.overrun++;
 			r1 &= up->port.read_status_mask;
 			if (r1 & BRK_ABRT)
-				*tty->flip.flag_buf_ptr = TTY_BREAK;
+				flag = TTY_BREAK;
 			else if (r1 & PAR_ERR)
-				*tty->flip.flag_buf_ptr = TTY_PARITY;
+				flag = TTY_PARITY;
 			else if (r1 & CRC_ERR)
-				*tty->flip.flag_buf_ptr = TTY_FRAME;
+				flag = TTY_FRAME;
 		}
 		if (uart_handle_sysrq_char(&up->port, ch, regs))
 			goto next_char;
 
 		if (up->port.ignore_status_mask == 0xff ||
-		    (r1 & up->port.ignore_status_mask) == 0) {
-			tty->flip.flag_buf_ptr++;
-			tty->flip.char_buf_ptr++;
-			tty->flip.count++;
-		}
-		if ((r1 & Rx_OVR) &&
-		    tty->flip.count < TTY_FLIPBUF_SIZE) {
-			*tty->flip.flag_buf_ptr = TTY_OVERRUN;
-			tty->flip.flag_buf_ptr++;
-			tty->flip.char_buf_ptr++;
-			tty->flip.count++;
-		}
+		    (r1 & up->port.ignore_status_mask) == 0)
+		    	tty_insert_flip_char(tty, ch, flag);
+
+		if (r1 & Rx_OVR)
+			tty_insert_flip_char(tty, 0, TTY_OVERRUN);
 	next_char:
 		ch = readb(&channel->control);
 		ZSDELAY();
diff --git a/drivers/serial/m32r_sio.c b/drivers/serial/m32r_sio.c
index b0ecc7537ce..b48066a64a7 100644
--- a/drivers/serial/m32r_sio.c
+++ b/drivers/serial/m32r_sio.c
@@ -331,17 +331,12 @@ static _INLINE_ void receive_chars(struct uart_sio_port *up, int *status,
 {
 	struct tty_struct *tty = up->port.info->tty;
 	unsigned char ch;
+	unsigned char flag;
 	int max_count = 256;
 
 	do {
-		if (unlikely(tty->flip.count >= TTY_FLIPBUF_SIZE)) {
-			tty->flip.work.func((void *)tty);
-			if (tty->flip.count >= TTY_FLIPBUF_SIZE)
-				return; // if TTY_DONT_FLIP is set
-		}
 		ch = sio_in(up, SIORXB);
-		*tty->flip.char_buf_ptr = ch;
-		*tty->flip.flag_buf_ptr = TTY_NORMAL;
+		flag = TTY_NORMAL;
 		up->port.icount.rx++;
 
 		if (unlikely(*status & (UART_LSR_BI | UART_LSR_PE |
@@ -380,30 +375,24 @@ static _INLINE_ void receive_chars(struct uart_sio_port *up, int *status,
 
 			if (*status & UART_LSR_BI) {
 				DEBUG_INTR("handling break....");
-				*tty->flip.flag_buf_ptr = TTY_BREAK;
+				flag = TTY_BREAK;
 			} else if (*status & UART_LSR_PE)
-				*tty->flip.flag_buf_ptr = TTY_PARITY;
+				flag = TTY_PARITY;
 			else if (*status & UART_LSR_FE)
-				*tty->flip.flag_buf_ptr = TTY_FRAME;
+				flag = TTY_FRAME;
 		}
 		if (uart_handle_sysrq_char(&up->port, ch, regs))
 			goto ignore_char;
-		if ((*status & up->port.ignore_status_mask) == 0) {
-			tty->flip.flag_buf_ptr++;
-			tty->flip.char_buf_ptr++;
-			tty->flip.count++;
-		}
-		if ((*status & UART_LSR_OE) &&
-		    tty->flip.count < TTY_FLIPBUF_SIZE) {
+		if ((*status & up->port.ignore_status_mask) == 0)
+			tty_insert_flip_char(tty, ch, flag);
+
+		if (*status & UART_LSR_OE) {
 			/*
 			 * Overrun is special, since it's reported
 			 * immediately, and doesn't affect the current
 			 * character.
 			 */
-			*tty->flip.flag_buf_ptr = TTY_OVERRUN;
-			tty->flip.flag_buf_ptr++;
-			tty->flip.char_buf_ptr++;
-			tty->flip.count++;
+			tty_insert_flip_char(tty, 0, TTY_OVERRUN);
 		}
 	ignore_char:
 		*status = serial_in(up, UART_LSR);
diff --git a/drivers/serial/mcfserial.c b/drivers/serial/mcfserial.c
index 47f7404cb04..f2a51e61eec 100644
--- a/drivers/serial/mcfserial.c
+++ b/drivers/serial/mcfserial.c
@@ -313,7 +313,7 @@ static inline void receive_chars(struct mcf_serial *info)
 {
 	volatile unsigned char	*uartp;
 	struct tty_struct	*tty = info->tty;
-	unsigned char		status, ch;
+	unsigned char		status, ch, flag;
 
 	if (!tty)
 		return;
@@ -321,10 +321,6 @@ static inline void receive_chars(struct mcf_serial *info)
 	uartp = info->addr;
 
 	while ((status = uartp[MCFUART_USR]) & MCFUART_USR_RXREADY) {
-
-		if (tty->flip.count >= TTY_FLIPBUF_SIZE)
-			break;
-
 		ch = uartp[MCFUART_URB];
 		info->stats.rx++;
 
@@ -335,29 +331,24 @@ static inline void receive_chars(struct mcf_serial *info)
 		}
 #endif
 
-		tty->flip.count++;
+		flag = TTY_NORMAL;
 		if (status & MCFUART_USR_RXERR) {
 			uartp[MCFUART_UCR] = MCFUART_UCR_CMDRESETERR;
 			if (status & MCFUART_USR_RXBREAK) {
 				info->stats.rxbreak++;
-				*tty->flip.flag_buf_ptr++ = TTY_BREAK;
+				flag = TTY_BREAK;
 			} else if (status & MCFUART_USR_RXPARITY) {
 				info->stats.rxparity++;
-				*tty->flip.flag_buf_ptr++ = TTY_PARITY;
+				flag = TTY_PARITY;
 			} else if (status & MCFUART_USR_RXOVERRUN) {
 				info->stats.rxoverrun++;
-				*tty->flip.flag_buf_ptr++ = TTY_OVERRUN;
+				flag = TTY_OVERRUN;
 			} else if (status & MCFUART_USR_RXFRAMING) {
 				info->stats.rxframing++;
-				*tty->flip.flag_buf_ptr++ = TTY_FRAME;
-			} else {
-				/* This should never happen... */
-				*tty->flip.flag_buf_ptr++ = 0;
+				flag = TTY_FRAME;
 			}
-		} else {
-			*tty->flip.flag_buf_ptr++ = 0;
 		}
-		*tty->flip.char_buf_ptr++ = ch;
+		tty_insert_flip_char(tty, ch, flag);
 	}
 
 	schedule_work(&tty->flip.work);
diff --git a/drivers/serial/mpc52xx_uart.c b/drivers/serial/mpc52xx_uart.c
index 1288d6203e9..61dd17d7bac 100644
--- a/drivers/serial/mpc52xx_uart.c
+++ b/drivers/serial/mpc52xx_uart.c
@@ -405,17 +405,13 @@ static inline int
 mpc52xx_uart_int_rx_chars(struct uart_port *port, struct pt_regs *regs)
 {
 	struct tty_struct *tty = port->info->tty;
-	unsigned char ch;
+	unsigned char ch, flag;
 	unsigned short status;
 
 	/* While we can read, do so ! */
 	while ( (status = in_be16(&PSC(port)->mpc52xx_psc_status)) &
 	        MPC52xx_PSC_SR_RXRDY) {
 
-		/* If we are full, just stop reading */
-		if (tty->flip.count >= TTY_FLIPBUF_SIZE)
-			break;
-		
 		/* Get the char */
 		ch = in_8(&PSC(port)->mpc52xx_psc_buffer_8);
 
@@ -428,45 +424,35 @@ mpc52xx_uart_int_rx_chars(struct uart_port *port, struct pt_regs *regs)
 #endif
 
 		/* Store it */
-		*tty->flip.char_buf_ptr = ch;
-		*tty->flip.flag_buf_ptr = 0;
+
+		flag = TTY_NORMAL;
 		port->icount.rx++;
 	
 		if ( status & (MPC52xx_PSC_SR_PE |
 		               MPC52xx_PSC_SR_FE |
-		               MPC52xx_PSC_SR_RB |
-		               MPC52xx_PSC_SR_OE) ) {
+		               MPC52xx_PSC_SR_RB) ) {
 			
 			if (status & MPC52xx_PSC_SR_RB) {
-				*tty->flip.flag_buf_ptr = TTY_BREAK;
+				flag = TTY_BREAK;
 				uart_handle_break(port);
 			} else if (status & MPC52xx_PSC_SR_PE)
-				*tty->flip.flag_buf_ptr = TTY_PARITY;
+				flag = TTY_PARITY;
 			else if (status & MPC52xx_PSC_SR_FE)
-				*tty->flip.flag_buf_ptr = TTY_FRAME;
-			if (status & MPC52xx_PSC_SR_OE) {
-				/*
-				 * Overrun is special, since it's
-				 * reported immediately, and doesn't
-				 * affect the current character
-				 */
-				if (tty->flip.count < (TTY_FLIPBUF_SIZE-1)) {
-					tty->flip.flag_buf_ptr++;
-					tty->flip.char_buf_ptr++;
-					tty->flip.count++;
-				}
-				*tty->flip.flag_buf_ptr = TTY_OVERRUN;
-			}
+				flag = TTY_FRAME;
 
 			/* Clear error condition */
 			out_8(&PSC(port)->command,MPC52xx_PSC_RST_ERR_STAT);
 
 		}
-
-		tty->flip.char_buf_ptr++;
-		tty->flip.flag_buf_ptr++;
-		tty->flip.count++;
-
+		tty_insert_flip_char(tty, ch, flag);
+		if (status & MPC52xx_PSC_SR_OE) {
+			/*
+			 * Overrun is special, since it's
+			 * reported immediately, and doesn't
+			 * affect the current character
+			 */
+			tty_insert_flip_char(tty, 0, TTY_OVERRUN);
+		}
 	}
 
 	tty_flip_buffer_push(tty);
diff --git a/drivers/serial/mpsc.c b/drivers/serial/mpsc.c
index 8f83e4007ec..0ca83ac31d0 100644
--- a/drivers/serial/mpsc.c
+++ b/drivers/serial/mpsc.c
@@ -769,12 +769,12 @@ mpsc_rx_intr(struct mpsc_port_info *pi, struct pt_regs *regs)
 		bytes_in = be16_to_cpu(rxre->bytecnt);
 
 		/* Following use of tty struct directly is deprecated */
-		if (unlikely((tty->flip.count + bytes_in) >= TTY_FLIPBUF_SIZE)){
+		if (unlikely(tty_buffer_request_room(tty, bytes_in) < bytes_in)) {
 			if (tty->low_latency)
 				tty_flip_buffer_push(tty);
 			/*
-			 * If this failed then we will throw awa the bytes
-			 * but mst do so to clear interrupts.
+			 * If this failed then we will throw away the bytes
+			 * but must do so to clear interrupts.
 			 */
 		}
 
diff --git a/drivers/serial/mux.c b/drivers/serial/mux.c
index 7633132a10a..4e49168c317 100644
--- a/drivers/serial/mux.c
+++ b/drivers/serial/mux.c
@@ -223,11 +223,6 @@ static void mux_read(struct uart_port *port)
 		if (MUX_EOFIFO(data))
 			break;
 
-		if (tty->flip.count >= TTY_FLIPBUF_SIZE)
-			continue;
-
-		*tty->flip.char_buf_ptr = data & 0xffu;
-		*tty->flip.flag_buf_ptr = TTY_NORMAL;
 		port->icount.rx++;
 
 		if (MUX_BREAK(data)) {
@@ -239,9 +234,7 @@ static void mux_read(struct uart_port *port)
 		if (uart_handle_sysrq_char(port, data & 0xffu, NULL))
 			continue;
 
-		tty->flip.flag_buf_ptr++;
-		tty->flip.char_buf_ptr++;
-		tty->flip.count++;
+		tty_insert_flip_char(tty, data & 0xFF, TTY_NORMAL);
 	}
 	
 	if (start_count != port->icount.rx) {
diff --git a/drivers/serial/pmac_zilog.c b/drivers/serial/pmac_zilog.c
index ea24129eb6b..f330d6c0e0d 100644
--- a/drivers/serial/pmac_zilog.c
+++ b/drivers/serial/pmac_zilog.c
@@ -210,10 +210,9 @@ static struct tty_struct *pmz_receive_chars(struct uart_pmac_port *uap,
 					    struct pt_regs *regs)
 {
 	struct tty_struct *tty = NULL;
-	unsigned char ch, r1, drop, error;
+	unsigned char ch, r1, drop, error, flag;
 	int loops = 0;
 
- retry:
 	/* The interrupt can be enabled when the port isn't open, typically
 	 * that happens when using one port is open and the other closed (stale
 	 * interrupt) or when one port is used as a console.
@@ -246,20 +245,6 @@ static struct tty_struct *pmz_receive_chars(struct uart_pmac_port *uap,
 		error = 0;
 		drop = 0;
 
-		if (unlikely(tty->flip.count >= TTY_FLIPBUF_SIZE)) {
-			/* Have to drop the lock here */
-			pmz_debug("pmz: flip overflow\n");
-			spin_unlock(&uap->port.lock);
-			tty->flip.work.func((void *)tty);
-			spin_lock(&uap->port.lock);
-			if (tty->flip.count >= TTY_FLIPBUF_SIZE)
-				drop = 1;
-			if (ZS_IS_ASLEEP(uap))
-				return NULL;
-			if (!ZS_IS_OPEN(uap))
-				goto retry;
-		}
-
 		r1 = read_zsreg(uap, R1);
 		ch = read_zsdata(uap);
 
@@ -295,8 +280,7 @@ static struct tty_struct *pmz_receive_chars(struct uart_pmac_port *uap,
 		if (drop)
 			goto next_char;
 
-		*tty->flip.char_buf_ptr = ch;
-		*tty->flip.flag_buf_ptr = TTY_NORMAL;
+		flag = TTY_NORMAL;
 		uap->port.icount.rx++;
 
 		if (r1 & (PAR_ERR | Rx_OVR | CRC_ERR | BRK_ABRT)) {
@@ -316,26 +300,19 @@ static struct tty_struct *pmz_receive_chars(struct uart_pmac_port *uap,
 				uap->port.icount.overrun++;
 			r1 &= uap->port.read_status_mask;
 			if (r1 & BRK_ABRT)
-				*tty->flip.flag_buf_ptr = TTY_BREAK;
+				flag = TTY_BREAK;
 			else if (r1 & PAR_ERR)
-				*tty->flip.flag_buf_ptr = TTY_PARITY;
+				flag = TTY_PARITY;
 			else if (r1 & CRC_ERR)
-				*tty->flip.flag_buf_ptr = TTY_FRAME;
+				flag = TTY_FRAME;
 		}
 
 		if (uap->port.ignore_status_mask == 0xff ||
 		    (r1 & uap->port.ignore_status_mask) == 0) {
-			tty->flip.flag_buf_ptr++;
-			tty->flip.char_buf_ptr++;
-			tty->flip.count++;
-		}
-		if ((r1 & Rx_OVR) &&
-		    tty->flip.count < TTY_FLIPBUF_SIZE) {
-			*tty->flip.flag_buf_ptr = TTY_OVERRUN;
-			tty->flip.flag_buf_ptr++;
-			tty->flip.char_buf_ptr++;
-			tty->flip.count++;
+		    	tty_insert_flip_char(tty, ch, flag);
 		}
+		if (r1 & Rx_OVR)
+			tty_insert_flip_char(tty, 0, TTY_OVERRUN);
 	next_char:
 		/* We can get stuck in an infinite loop getting char 0 when the
 		 * line is in a wrong HW state, we break that here.
diff --git a/drivers/serial/pxa.c b/drivers/serial/pxa.c
index cc998b99a19..10535f00301 100644
--- a/drivers/serial/pxa.c
+++ b/drivers/serial/pxa.c
@@ -107,14 +107,6 @@ receive_chars(struct uart_pxa_port *up, int *status, struct pt_regs *regs)
 	int max_count = 256;
 
 	do {
-		if (unlikely(tty->flip.count >= TTY_FLIPBUF_SIZE)) {
-			if (tty->low_latency)
-				tty_flip_buffer_push(tty);
-			/*
-			 * If this failed then we will throw away the
-			 * bytes but must do so to clear interrupts
-			 */
-		}
 		ch = serial_in(up, UART_RX);
 		flag = TTY_NORMAL;
 		up->port.icount.rx++;
diff --git a/drivers/serial/s3c2410.c b/drivers/serial/s3c2410.c
index fe83ce6fef5..eb4883efb7c 100644
--- a/drivers/serial/s3c2410.c
+++ b/drivers/serial/s3c2410.c
@@ -323,16 +323,6 @@ s3c24xx_serial_rx_chars(int irq, void *dev_id, struct pt_regs *regs)
 		if (s3c24xx_serial_rx_fifocnt(ourport, ufstat) == 0)
 			break;
 
-		if (tty->flip.count >= TTY_FLIPBUF_SIZE) {
-			if (tty->low_latency)
-				tty_flip_buffer_push(tty);
-
-			/*
-			 * If this failed then we will throw away the
-			 * bytes but must do so to clear interrupts
-			 */
-		}
-
 		uerstat = rd_regl(port, S3C2410_UERSTAT);
 		ch = rd_regb(port, S3C2410_URXH);
 
diff --git a/drivers/serial/sa1100.c b/drivers/serial/sa1100.c
index 25a086458ab..1bd93168f50 100644
--- a/drivers/serial/sa1100.c
+++ b/drivers/serial/sa1100.c
@@ -201,8 +201,6 @@ sa1100_rx_chars(struct sa1100_port *sport, struct pt_regs *regs)
 	while (status & UTSR1_TO_SM(UTSR1_RNE)) {
 		ch = UART_GET_CHAR(sport);
 
-		if (tty->flip.count >= TTY_FLIPBUF_SIZE)
-			goto ignore_char;
 		sport->port.icount.rx++;
 
 		flg = TTY_NORMAL;
diff --git a/drivers/serial/serial_lh7a40x.c b/drivers/serial/serial_lh7a40x.c
index d01dbe5da3b..d4a1f0e798c 100644
--- a/drivers/serial/serial_lh7a40x.c
+++ b/drivers/serial/serial_lh7a40x.c
@@ -148,15 +148,6 @@ lh7a40xuart_rx_chars (struct uart_port* port)
 	unsigned int data, flag;/* Received data and status */
 
 	while (!(UR (port, UART_R_STATUS) & nRxRdy) && --cbRxMax) {
-		if (tty->flip.count >= TTY_FLIPBUF_SIZE) {
-			if (tty->low_latency)
-				tty_flip_buffer_push(tty);
-			/*
-			 * If this failed then we will throw away the
-			 * bytes but must do so to clear interrupts
-			 */
-		}
-
 		data = UR (port, UART_R_DATA);
 		flag = TTY_NORMAL;
 		++port->icount.rx;
diff --git a/drivers/serial/serial_txx9.c b/drivers/serial/serial_txx9.c
index 995d9dd9ddd..fdd1f1915a4 100644
--- a/drivers/serial/serial_txx9.c
+++ b/drivers/serial/serial_txx9.c
@@ -303,17 +303,6 @@ receive_chars(struct uart_txx9_port *up, unsigned int *status, struct pt_regs *r
 	char flag;
 
 	do {
-		/* The following is not allowed by the tty layer and
-		   unsafe. It should be fixed ASAP */
-		if (unlikely(tty->flip.count >= TTY_FLIPBUF_SIZE)) {
-			if (tty->low_latency) {
-				spin_unlock(&up->port.lock);
-				tty_flip_buffer_push(tty);
-				spin_lock(&up->port.lock);
-			}
-			/* If this failed then we will throw away the
-			   bytes but must do so to clear interrupts */
-		}
 		ch = sio_in(up, TXX9_SIRFIFO);
 		flag = TTY_NORMAL;
 		up->port.icount.rx++;
diff --git a/drivers/serial/sh-sci.c b/drivers/serial/sh-sci.c
index 430754ebac8..a9e07075962 100644
--- a/drivers/serial/sh-sci.c
+++ b/drivers/serial/sh-sci.c
@@ -482,6 +482,7 @@ static inline void sci_receive_chars(struct uart_port *port,
 	struct tty_struct *tty = port->info->tty;
 	int i, count, copied = 0;
 	unsigned short status;
+	unsigned char flag;
 
 	status = sci_in(port, SCxSR);
 	if (!(status & SCxSR_RDxF(port)))
@@ -499,8 +500,7 @@ static inline void sci_receive_chars(struct uart_port *port,
 #endif
 
 		/* Don't copy more bytes than there is room for in the buffer */
-		if (tty->flip.count + count > TTY_FLIPBUF_SIZE)
-			count = TTY_FLIPBUF_SIZE - tty->flip.count;
+		count = tty_buffer_request_room(tty, count);
 
 		/* If for any reason we can't copy more data, we're done! */
 		if (count == 0)
@@ -512,8 +512,7 @@ static inline void sci_receive_chars(struct uart_port *port,
 			    || uart_handle_sysrq_char(port, c, regs)) {
 				count = 0;
 			} else {
-			    tty->flip.char_buf_ptr[0] = c;
-			    tty->flip.flag_buf_ptr[0] = TTY_NORMAL;
+			    tty_insert_flip_char(tty, c, TTY_NORMAL);
 			}
 		} else {
 			for (i=0; i<count; i++) {
@@ -542,26 +541,21 @@ static inline void sci_receive_chars(struct uart_port *port,
 				}
 
 				/* Store data and status */
-				tty->flip.char_buf_ptr[i] = c;
 				if (status&SCxSR_FER(port)) {
-					tty->flip.flag_buf_ptr[i] = TTY_FRAME;
+					flag = TTY_FRAME;
 					pr_debug("sci: frame error\n");
 				} else if (status&SCxSR_PER(port)) {
-					tty->flip.flag_buf_ptr[i] = TTY_PARITY;
+					flag = TTY_PARITY;
 					pr_debug("sci: parity error\n");
-				} else {
-					tty->flip.flag_buf_ptr[i] = TTY_NORMAL;
-				}
+				} else
+					flag = TTY_NORMAL;
+				tty_insert_flip_char(tty, c, flag);
 			}
 		}
 
 		sci_in(port, SCxSR); /* dummy read */
 		sci_out(port, SCxSR, SCxSR_RDxF_CLEAR(port));
 
-		/* Update the kernel buffer end */
-		tty->flip.count += count;
-		tty->flip.char_buf_ptr += count;
-		tty->flip.flag_buf_ptr += count;
 		copied += count;
 		port->icount.rx += count;
 	}
@@ -608,48 +602,45 @@ static inline int sci_handle_errors(struct uart_port *port)
 	unsigned short status = sci_in(port, SCxSR);
 	struct tty_struct *tty = port->info->tty;
 
-	if (status&SCxSR_ORER(port) && tty->flip.count<TTY_FLIPBUF_SIZE) {
+	if (status&SCxSR_ORER(port)) {
 		/* overrun error */
-		copied++;
-		*tty->flip.flag_buf_ptr++ = TTY_OVERRUN;
+		if(tty_insert_flip_char(tty, 0, TTY_OVERRUN))
+			copied++;
 		pr_debug("sci: overrun error\n");
 	}
 
-	if (status&SCxSR_FER(port) && tty->flip.count<TTY_FLIPBUF_SIZE) {
+	if (status&SCxSR_FER(port)) {
 		if (sci_rxd_in(port) == 0) {
 			/* Notify of BREAK */
 			struct sci_port * sci_port = (struct sci_port *)port;
-                       if(!sci_port->break_flag) {
-	                        sci_port->break_flag = 1;
-                               sci_schedule_break_timer((struct sci_port *)port);
+			if(!sci_port->break_flag) {
+	                	sci_port->break_flag = 1;
+	                	sci_schedule_break_timer((struct sci_port *)port);
 				/* Do sysrq handling. */
-				if(uart_handle_break(port)) {
+				if(uart_handle_break(port))
 					return 0;
-				}
 			        pr_debug("sci: BREAK detected\n");
-			        copied++;
-			        *tty->flip.flag_buf_ptr++ = TTY_BREAK;
+			        if(tty_insert_flip_char(tty, 0, TTY_BREAK))
+				        copied++;
                        }
 		}
 		else {
 			/* frame error */
-			copied++;
-			*tty->flip.flag_buf_ptr++ = TTY_FRAME;
+			if(tty_insert_flip_char(tty, 0, TTY_FRAME))
+				copied++;
 			pr_debug("sci: frame error\n");
 		}
 	}
 
-	if (status&SCxSR_PER(port) && tty->flip.count<TTY_FLIPBUF_SIZE) {
+	if (status&SCxSR_PER(port)) {
+		if(tty_insert_flip_char(tty, 0, TTY_PARITY))
+			copied++;
 		/* parity error */
-		copied++;
-		*tty->flip.flag_buf_ptr++ = TTY_PARITY;
 		pr_debug("sci: parity error\n");
 	}
 
-	if (copied) {
-		tty->flip.count += copied;
+	if (copied)
 		tty_flip_buffer_push(tty);
-	}
 
 	return copied;
 }
@@ -661,15 +652,14 @@ static inline int sci_handle_breaks(struct uart_port *port)
 	struct tty_struct *tty = port->info->tty;
 	struct sci_port *s = &sci_ports[port->line];
 
-	if (!s->break_flag && status & SCxSR_BRK(port) &&
-	    tty->flip.count < TTY_FLIPBUF_SIZE) {
+	if (!s->break_flag && status & SCxSR_BRK(port))
 #if defined(CONFIG_CPU_SH3)
 		/* Debounce break */
 		s->break_flag = 1;
 #endif
 		/* Notify of BREAK */
-		copied++;
-		*tty->flip.flag_buf_ptr++ = TTY_BREAK;
+		if(tty_insert_flip_char(tty, 0, TTY_BREAK))
+			copied++;
 		pr_debug("sci: BREAK detected\n");
 	}
 
@@ -677,19 +667,15 @@ static inline int sci_handle_breaks(struct uart_port *port)
 	/* XXX: Handle SCIF overrun error */
 	if (port->type == PORT_SCIF && (sci_in(port, SCLSR) & SCIF_ORER) != 0) {
 		sci_out(port, SCLSR, 0);
-		if(tty->flip.count<TTY_FLIPBUF_SIZE) {
+		if(tty_insert_flip_char(tty, 0, TTY_OVERRUN)) {
 			copied++;
-			*tty->flip.flag_buf_ptr++ = TTY_OVERRUN;
 			pr_debug("sci: overrun error\n");
 		}
 	}
 #endif
 
-	if (copied) {
-		tty->flip.count += copied;
+	if (copied)
 		tty_flip_buffer_push(tty);
-	}
-
 	return copied;
 }
 
@@ -732,12 +718,9 @@ static irqreturn_t sci_er_interrupt(int irq, void *ptr, struct pt_regs *regs)
 			struct tty_struct *tty = port->info->tty;
 
 			sci_out(port, SCLSR, 0);
-			if(tty->flip.count<TTY_FLIPBUF_SIZE) {
-				*tty->flip.flag_buf_ptr++ = TTY_OVERRUN;
-				tty->flip.count++;
-				tty_flip_buffer_push(tty);
-				pr_debug("scif: overrun error\n");
-			}
+			tty_insert_flip_char(tty, 0, TTY_OVERRUN);
+			tty_flip_buffer_push(tty);
+			pr_debug("scif: overrun error\n");
 		}
 #endif
 		sci_rx_interrupt(irq, ptr, regs);
diff --git a/drivers/serial/sn_console.c b/drivers/serial/sn_console.c
index 313f9df24a2..5468e5a767e 100644
--- a/drivers/serial/sn_console.c
+++ b/drivers/serial/sn_console.c
@@ -519,11 +519,7 @@ sn_receive_chars(struct sn_cons_port *port, struct pt_regs *regs,
 
 		/* record the character to pass up to the tty layer */
 		if (tty) {
-			*tty->flip.char_buf_ptr = ch;
-			*tty->flip.flag_buf_ptr = TTY_NORMAL;
-			tty->flip.char_buf_ptr++;
-			tty->flip.count++;
-			if (tty->flip.count == TTY_FLIPBUF_SIZE)
+			if(tty_insert_flip_char(tty, ch, TTY_NORMAL) == 0)
 				break;
 		}
 		port->sc_port.icount.rx++;
diff --git a/drivers/serial/sunsab.c b/drivers/serial/sunsab.c
index ba9381fd3f2..7e773ff76c6 100644
--- a/drivers/serial/sunsab.c
+++ b/drivers/serial/sunsab.c
@@ -159,21 +159,14 @@ receive_chars(struct uart_sunsab_port *up,
 		saw_console_brk = 1;
 
 	for (i = 0; i < count; i++) {
-		unsigned char ch = buf[i];
+		unsigned char ch = buf[i], flag;
 
 		if (tty == NULL) {
 			uart_handle_sysrq_char(&up->port, ch, regs);
 			continue;
 		}
 
-		if (unlikely(tty->flip.count >= TTY_FLIPBUF_SIZE)) {
-			tty->flip.work.func((void *)tty);
-			if (tty->flip.count >= TTY_FLIPBUF_SIZE)
-				return tty; // if TTY_DONT_FLIP is set
-		}
-
-		*tty->flip.char_buf_ptr = ch;
-		*tty->flip.flag_buf_ptr = TTY_NORMAL;
+		flag = TTY_NORMAL;
 		up->port.icount.rx++;
 
 		if (unlikely(stat->sreg.isr0 & (SAB82532_ISR0_PERR |
@@ -209,34 +202,21 @@ receive_chars(struct uart_sunsab_port *up,
 			stat->sreg.isr1 &= ((up->port.read_status_mask >> 8) & 0xff);
 
 			if (stat->sreg.isr1 & SAB82532_ISR1_BRK) {
-				*tty->flip.flag_buf_ptr = TTY_BREAK;
+				flag = TTY_BREAK;
 			} else if (stat->sreg.isr0 & SAB82532_ISR0_PERR)
-				*tty->flip.flag_buf_ptr = TTY_PARITY;
+				flag = TTY_PARITY;
 			else if (stat->sreg.isr0 & SAB82532_ISR0_FERR)
-				*tty->flip.flag_buf_ptr = TTY_FRAME;
+				flag = TTY_FRAME;
 		}
 
 		if (uart_handle_sysrq_char(&up->port, ch, regs))
 			continue;
 
 		if ((stat->sreg.isr0 & (up->port.ignore_status_mask & 0xff)) == 0 &&
-		    (stat->sreg.isr1 & ((up->port.ignore_status_mask >> 8) & 0xff)) == 0){
-			tty->flip.flag_buf_ptr++;
-			tty->flip.char_buf_ptr++;
-			tty->flip.count++;
-		}
-		if ((stat->sreg.isr0 & SAB82532_ISR0_RFO) &&
-		    tty->flip.count < TTY_FLIPBUF_SIZE) {
-			/*
-			 * Overrun is special, since it's reported
-			 * immediately, and doesn't affect the current
-			 * character.
-			 */
-			*tty->flip.flag_buf_ptr = TTY_OVERRUN;
-			tty->flip.flag_buf_ptr++;
-			tty->flip.char_buf_ptr++;
-			tty->flip.count++;
-		}
+		    (stat->sreg.isr1 & ((up->port.ignore_status_mask >> 8) & 0xff)) == 0)
+			tty_insert_flip_char(tty, ch, flag);
+		if (stat->sreg.isr0 & SAB82532_ISR0_RFO)
+			tty_insert_flip_char(tty, 0, TTY_OVERRUN);
 	}
 
 	if (saw_console_brk)
diff --git a/drivers/serial/sunsu.c b/drivers/serial/sunsu.c
index f0738533f39..9a3665b34d9 100644
--- a/drivers/serial/sunsu.c
+++ b/drivers/serial/sunsu.c
@@ -323,19 +323,13 @@ static _INLINE_ struct tty_struct *
 receive_chars(struct uart_sunsu_port *up, unsigned char *status, struct pt_regs *regs)
 {
 	struct tty_struct *tty = up->port.info->tty;
-	unsigned char ch;
+	unsigned char ch, flag;
 	int max_count = 256;
 	int saw_console_brk = 0;
 
 	do {
-		if (unlikely(tty->flip.count >= TTY_FLIPBUF_SIZE)) {
-			tty->flip.work.func((void *)tty);
-			if (tty->flip.count >= TTY_FLIPBUF_SIZE)
-				return tty; // if TTY_DONT_FLIP is set
-		}
 		ch = serial_inp(up, UART_RX);
-		*tty->flip.char_buf_ptr = ch;
-		*tty->flip.flag_buf_ptr = TTY_NORMAL;
+		flag = TTY_NORMAL;
 		up->port.icount.rx++;
 
 		if (unlikely(*status & (UART_LSR_BI | UART_LSR_PE |
@@ -377,31 +371,23 @@ receive_chars(struct uart_sunsu_port *up, unsigned char *status, struct pt_regs
 			}
 
 			if (*status & UART_LSR_BI) {
-				*tty->flip.flag_buf_ptr = TTY_BREAK;
+				flag = TTY_BREAK;
 			} else if (*status & UART_LSR_PE)
-				*tty->flip.flag_buf_ptr = TTY_PARITY;
+				flag = TTY_PARITY;
 			else if (*status & UART_LSR_FE)
-				*tty->flip.flag_buf_ptr = TTY_FRAME;
+				flag = TTY_FRAME;
 		}
 		if (uart_handle_sysrq_char(&up->port, ch, regs))
 			goto ignore_char;
-		if ((*status & up->port.ignore_status_mask) == 0) {
-			tty->flip.flag_buf_ptr++;
-			tty->flip.char_buf_ptr++;
-			tty->flip.count++;
-		}
-		if ((*status & UART_LSR_OE) &&
-		    tty->flip.count < TTY_FLIPBUF_SIZE) {
+		if ((*status & up->port.ignore_status_mask) == 0)
+			tty_insert_flip_char(tty, ch, flag);
+		if (*status & UART_LSR_OE)
 			/*
 			 * Overrun is special, since it's reported
 			 * immediately, and doesn't affect the current
 			 * character.
 			 */
-			*tty->flip.flag_buf_ptr = TTY_OVERRUN;
-			tty->flip.flag_buf_ptr++;
-			tty->flip.char_buf_ptr++;
-			tty->flip.count++;
-		}
+			 tty_insert_flip_char(tty, 0, TTY_OVERRUN);
 	ignore_char:
 		*status = serial_inp(up, UART_LSR);
 	} while ((*status & UART_LSR_DR) && (max_count-- > 0));
diff --git a/drivers/serial/sunzilog.c b/drivers/serial/sunzilog.c
index 7653d6cf05a..3c72484adea 100644
--- a/drivers/serial/sunzilog.c
+++ b/drivers/serial/sunzilog.c
@@ -319,7 +319,7 @@ sunzilog_receive_chars(struct uart_sunzilog_port *up,
 		       struct pt_regs *regs)
 {
 	struct tty_struct *tty;
-	unsigned char ch, r1;
+	unsigned char ch, r1, flag;
 
 	tty = NULL;
 	if (up->port.info != NULL &&		/* Unopened serial console */
@@ -362,19 +362,8 @@ sunzilog_receive_chars(struct uart_sunzilog_port *up,
 			continue;
 		}
 
-		if (unlikely(tty->flip.count >= TTY_FLIPBUF_SIZE)) {
-			tty->flip.work.func((void *)tty);
-			/*
-			 * The 8250 bails out of the loop here,
-			 * but we need to read everything, or die.
-			 */
-			if (tty->flip.count >= TTY_FLIPBUF_SIZE)
-				continue;
-		}
-
 		/* A real serial line, record the character and status.  */
-		*tty->flip.char_buf_ptr = ch;
-		*tty->flip.flag_buf_ptr = TTY_NORMAL;
+		flag = TTY_NORMAL;
 		up->port.icount.rx++;
 		if (r1 & (BRK_ABRT | PAR_ERR | Rx_OVR | CRC_ERR)) {
 			if (r1 & BRK_ABRT) {
@@ -391,28 +380,21 @@ sunzilog_receive_chars(struct uart_sunzilog_port *up,
 				up->port.icount.overrun++;
 			r1 &= up->port.read_status_mask;
 			if (r1 & BRK_ABRT)
-				*tty->flip.flag_buf_ptr = TTY_BREAK;
+				flag = TTY_BREAK;
 			else if (r1 & PAR_ERR)
-				*tty->flip.flag_buf_ptr = TTY_PARITY;
+				flag = TTY_PARITY;
 			else if (r1 & CRC_ERR)
-				*tty->flip.flag_buf_ptr = TTY_FRAME;
+				flag = TTY_FRAME;
 		}
 		if (uart_handle_sysrq_char(&up->port, ch, regs))
 			continue;
 
 		if (up->port.ignore_status_mask == 0xff ||
 		    (r1 & up->port.ignore_status_mask) == 0) {
-			tty->flip.flag_buf_ptr++;
-			tty->flip.char_buf_ptr++;
-			tty->flip.count++;
-		}
-		if ((r1 & Rx_OVR) &&
-		    tty->flip.count < TTY_FLIPBUF_SIZE) {
-			*tty->flip.flag_buf_ptr = TTY_OVERRUN;
-			tty->flip.flag_buf_ptr++;
-			tty->flip.char_buf_ptr++;
-			tty->flip.count++;
+		    	tty_insert_flip_char(tty, ch, flag);
 		}
+		if (r1 & Rx_OVR)
+			tty_insert_flip_char(tty, 0, TTY_OVERRUN);
 	}
 
 	return tty;
diff --git a/drivers/serial/vr41xx_siu.c b/drivers/serial/vr41xx_siu.c
index 865d4dea65d..0a28deeb098 100644
--- a/drivers/serial/vr41xx_siu.c
+++ b/drivers/serial/vr41xx_siu.c
@@ -371,11 +371,6 @@ static inline void receive_chars(struct uart_port *port, uint8_t *status,
 	lsr = *status;
 
 	do {
-		if (unlikely(tty->flip.count >= TTY_FLIPBUF_SIZE)) {
-			if (tty->low_latency)
-				tty_flip_buffer_push(tty);
-		}
-
 		ch = siu_read(port, UART_RX);
 		port->icount.rx++;
 		flag = TTY_NORMAL;