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tty: Remove chars_in_buffer() line discipline method

Browse source 
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: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley 2016-01-10 22:40:54 -08:00 committed by Greg Kroah-Hartman
parent 582e20a03b
commit fdfb719e93
8 changed files with 13 additions and 68 deletions
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3
Documentation/serial/tty.txt
View file

@ -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

6
drivers/tty/amiserial.c
View file

@ -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"))

8
drivers/tty/cyclades.c
View file

@ -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"))

16
drivers/tty/n_gsm.c
View file

@ -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,

23
drivers/tty/n_tty.c
View file

@ -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,

6
drivers/tty/rocket.c
View file

@ -1360,8 +1360,7 @@ static void rp_throttle(struct tty_struct *tty)
struct r_port *info = tty->driver_data;
#ifdef ROCKET_DEBUG_THROTTLE
printk(KERN_INFO "throttle %s: %d....\n", tty->name,
tty->ldisc.chars_in_buffer(tty));
printk(KERN_INFO "throttle %s ....\n", tty->name);
#endif
if (rocket_paranoia_check(info, "rp_throttle"))
@ -1377,8 +1376,7 @@ static void rp_unthrottle(struct tty_struct *tty)
{
struct r_port *info = tty->driver_data;
#ifdef ROCKET_DEBUG_THROTTLE
printk(KERN_INFO "unthrottle %s: %d....\n", tty->name,
tty->ldisc.chars_in_buffer(tty));
printk(KERN_INFO "unthrottle %s ....\n", tty->name);
#endif
if (rocket_paranoia_check(info, "rp_unthrottle"))

12
drivers/tty/serial/crisv10.c
View file

@ -2968,7 +2968,7 @@ static int rs_raw_write(struct tty_struct *tty,
local_save_flags(flags);
DFLOW(DEBUG_LOG(info->line, "write count %i ", count));
DFLOW(DEBUG_LOG(info->line, "ldisc %i\n", tty->ldisc.chars_in_buffer(tty)));
DFLOW(DEBUG_LOG(info->line, "ldisc\n"));
/* The local_irq_disable/restore_flags pairs below are needed
@ -3161,10 +3161,9 @@ rs_throttle(struct tty_struct * tty)
{
struct e100_serial *info = (struct e100_serial *)tty->driver_data;
#ifdef SERIAL_DEBUG_THROTTLE
printk("throttle %s: %lu....\n", tty_name(tty),
(unsigned long)tty->ldisc.chars_in_buffer(tty));
printk("throttle %s ....\n", tty_name(tty));
#endif
DFLOW(DEBUG_LOG(info->line,"rs_throttle %lu\n", tty->ldisc.chars_in_buffer(tty)));
DFLOW(DEBUG_LOG(info->line,"rs_throttle\n"));
/* Do RTS before XOFF since XOFF might take some time */
if (tty->termios.c_cflag & CRTSCTS) {
@ -3181,10 +3180,9 @@ rs_unthrottle(struct tty_struct * tty)
{
struct e100_serial *info = (struct e100_serial *)tty->driver_data;
#ifdef SERIAL_DEBUG_THROTTLE
printk("unthrottle %s: %lu....\n", tty_name(tty),
(unsigned long)tty->ldisc.chars_in_buffer(tty));
printk("unthrottle %s ....\n", tty_name(tty));
#endif
DFLOW(DEBUG_LOG(info->line,"rs_unthrottle ldisc %d\n", tty->ldisc.chars_in_buffer(tty)));
DFLOW(DEBUG_LOG(info->line,"rs_unthrottle ldisc\n"));
DFLOW(DEBUG_LOG(info->line,"rs_unthrottle flip.count: %i\n", tty->flip.count));
/* Do RTS before XOFF since XOFF might take some time */
if (tty->termios.c_cflag & CRTSCTS) {

7
include/linux/tty_ldisc.h
View file

@ -25,12 +25,6 @@
* buffers of any input characters it may have queued to be
* delivered to the user mode process.
*
* ssize_t (*chars_in_buffer)(struct tty_struct *tty);
*
* This function returns the number of input characters the line
* discipline may have queued up to be delivered to the user mode
* process.
*
* ssize_t (*read)(struct tty_struct * tty, struct file * file,
* unsigned char * buf, size_t nr);
*
@ -188,7 +182,6 @@ struct tty_ldisc_ops {
int (*open)(struct tty_struct *);
void (*close)(struct tty_struct *);
void (*flush_buffer)(struct tty_struct *tty);
ssize_t (*chars_in_buffer)(struct tty_struct *tty);
ssize_t (*read)(struct tty_struct *tty, struct file *file,
unsigned char __user *buf, size_t nr);
ssize_t (*write)(struct tty_struct *tty, struct file *file,