Commit fdfb719e authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
Browse files

tty: Remove chars_in_buffer() line discipline method 



The chars_in_buffer() line discipline method serves no functional
purpose, other than as a (dubious) debugging aid for mostly bit-rotting
drivers. Despite being documented as an optional method, every caller
is unconditionally executed (although conditionally compiled).
Furthermore, direct tty->ldisc access without an ldisc ref is unsafe.
Lastly, N_TTY's chars_in_buffer() has warned of removal since 3.12.

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 582e20a0

Documentation/serial/tty.txt

+0 −3
Original line number Diff line number Diff line
@@ -72,9 +72,6 @@ flush_buffer() - (optional) May be called at any point between 
			open and close, and instructs the line discipline

			to empty its input buffer.



chars_in_buffer() -	(optional) Report the number of bytes in the input

			buffer.



set_termios()	-	(optional) Called on termios structure changes.

			The caller passes the old termios data and the

			current data is in the tty. Called under the

drivers/tty/amiserial.c

+2 −4
Original line number Diff line number Diff line
@@ -965,8 +965,7 @@ static void rs_throttle(struct tty_struct * tty) 
	struct serial_state *info = tty->driver_data;

	unsigned long flags;

#ifdef SERIAL_DEBUG_THROTTLE

	printk("throttle %s: %d....\n", tty_name(tty),

	       tty->ldisc.chars_in_buffer(tty));

	printk("throttle %s ....\n", tty_name(tty));

#endif



	if (serial_paranoia_check(info, tty->name, "rs_throttle"))
@@ -988,8 +987,7 @@ static void rs_unthrottle(struct tty_struct * tty) 
	struct serial_state *info = tty->driver_data;

	unsigned long flags;

#ifdef SERIAL_DEBUG_THROTTLE

	printk("unthrottle %s: %d....\n", tty_name(tty),

	       tty->ldisc.chars_in_buffer(tty));

	printk("unthrottle %s ....\n", tty_name(tty));

#endif



	if (serial_paranoia_check(info, tty->name, "rs_unthrottle"))

drivers/tty/cyclades.c

+4 −4
Original line number Diff line number Diff line
@@ -2852,8 +2852,8 @@ static void cy_throttle(struct tty_struct *tty) 
	unsigned long flags;



#ifdef CY_DEBUG_THROTTLE

	printk(KERN_DEBUG "cyc:throttle %s: %ld...ttyC%d\n", tty_name(tty),

			tty->ldisc.chars_in_buffer(tty), info->line);

	printk(KERN_DEBUG "cyc:throttle %s ...ttyC%d\n", tty_name(tty),

			 info->line);

#endif



	if (serial_paranoia_check(info, tty->name, "cy_throttle"))
@@ -2891,8 +2891,8 @@ static void cy_unthrottle(struct tty_struct *tty) 
	unsigned long flags;



#ifdef CY_DEBUG_THROTTLE

	printk(KERN_DEBUG "cyc:unthrottle %s: %ld...ttyC%d\n",

		tty_name(tty), tty_chars_in_buffer(tty), info->line);

	printk(KERN_DEBUG "cyc:unthrottle %s ...ttyC%d\n",

		tty_name(tty), info->line);

#endif



	if (serial_paranoia_check(info, tty->name, "cy_unthrottle"))

drivers/tty/n_gsm.c

+0 −16
Original line number Diff line number Diff line
@@ -2303,21 +2303,6 @@ static void gsmld_receive_buf(struct tty_struct *tty, const unsigned char *cp, 
	/* If clogged call tty_throttle(tty); */

}



/**

 *	gsmld_chars_in_buffer	-	report available bytes

 *	@tty: tty device

 *

 *	Report the number of characters buffered to be delivered to user

 *	at this instant in time.

 *

 *	Locking: gsm lock

 */



static ssize_t gsmld_chars_in_buffer(struct tty_struct *tty)

{

	return 0;

}



/**

 *	gsmld_flush_buffer	-	clean input queue

 *	@tty:	terminal device
@@ -2830,7 +2815,6 @@ static struct tty_ldisc_ops tty_ldisc_packet = { 
	.open            = gsmld_open,

	.close           = gsmld_close,

	.flush_buffer    = gsmld_flush_buffer,

	.chars_in_buffer = gsmld_chars_in_buffer,

	.read            = gsmld_read,

	.write           = gsmld_write,

	.ioctl           = gsmld_ioctl,

drivers/tty/n_tty.c

+0 −23
Original line number Diff line number Diff line
@@ -380,28 +380,6 @@ static void n_tty_flush_buffer(struct tty_struct *tty) 
	up_write(&tty->termios_rwsem);

}



/**

 *	n_tty_chars_in_buffer	-	report available bytes

 *	@tty: tty device

 *

 *	Report the number of characters buffered to be delivered to user

 *	at this instant in time.

 *

 *	Locking: exclusive termios_rwsem

 */



static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)

{

	ssize_t n;



	WARN_ONCE(1, "%s is deprecated and scheduled for removal.", __func__);



	down_write(&tty->termios_rwsem);

	n = chars_in_buffer(tty);

	up_write(&tty->termios_rwsem);

	return n;

}



/**

 *	is_utf8_continuation	-	utf8 multibyte check

 *	@c: byte to check
@@ -2525,7 +2503,6 @@ struct tty_ldisc_ops tty_ldisc_N_TTY = { 
	.open            = n_tty_open,

	.close           = n_tty_close,

	.flush_buffer    = n_tty_flush_buffer,

	.chars_in_buffer = n_tty_chars_in_buffer,

	.read            = n_tty_read,

	.write           = n_tty_write,

	.ioctl           = n_tty_ioctl,