tty: remove tty_operations::chars_in_buffer for non-buffering

The only user of tty_ops::chars_in_buffer is tty_chars_in_buffer. And it
considers tty_ops::chars_in_buffer optional. In case it's NULL, zero is
returned. So remove all those chars_in_buffer from tty_ops which return
zero. (Zero means such driver doesn't buffer.)
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Richard Henderson <rth@twiddle.net>
Acked-by: Max Filippov <jcmvbkbc@gmail.com> # xtensa
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Chris Zankel <chris@zankel.net>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Link: https://lore.kernel.org/r/20210505091928.22010-26-jslaby@suse.czSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/alpha/kernel/srmcons.c

@@ -148,12 +148,6 @@ srmcons_write_room(struct tty_struct *tty)
 	return 512;
 }
 
-static int
-srmcons_chars_in_buffer(struct tty_struct *tty)
-{
-	return 0;
-}
-
 static int
 srmcons_open(struct tty_struct *tty, struct file *filp)
 {
@@ -200,7 +194,6 @@ static const struct tty_operations srmcons_ops = {
 	.close		= srmcons_close,
 	.write		= srmcons_write,
 	.write_room	= srmcons_write_room,
-	.chars_in_buffer= srmcons_chars_in_buffer,
 };
 
 static int __init

arch/parisc/kernel/pdc_cons.c

@@ -108,17 +108,11 @@ static unsigned int pdc_console_tty_write_room(struct tty_struct *tty)
 	return 32768; /* no limit, no buffer used */
 }
 
-static int pdc_console_tty_chars_in_buffer(struct tty_struct *tty)
-{
-	return 0; /* no buffer */
-}
-
 static const struct tty_operations pdc_console_tty_ops = {
 	.open = pdc_console_tty_open,
 	.close = pdc_console_tty_close,
 	.write = pdc_console_tty_write,
 	.write_room = pdc_console_tty_write_room,
-	.chars_in_buffer = pdc_console_tty_chars_in_buffer,
 };
 
 static void pdc_console_poll(struct timer_list *unused)

arch/xtensa/platforms/iss/console.c

@@ -106,12 +106,6 @@ static unsigned int rs_write_room(struct tty_struct *tty)
 	return 2 * 1024;
 }
 
-static int rs_chars_in_buffer(struct tty_struct *tty)
-{
-	/* the iss doesn't buffer characters */
-	return 0;
-}
-
 static void rs_hangup(struct tty_struct *tty)
 {
 	/* Stub, once again.. */
@@ -135,7 +129,6 @@ static const struct tty_operations serial_ops = {
 	.put_char = rs_put_char,
 	.flush_chars = rs_flush_chars,
 	.write_room = rs_write_room,
-	.chars_in_buffer = rs_chars_in_buffer,
 	.hangup = rs_hangup,
 	.wait_until_sent = rs_wait_until_sent,
 	.proc_show = rs_proc_show,

drivers/s390/char/tty3270.c

@@ -1756,17 +1756,6 @@ tty3270_flush_chars(struct tty_struct *tty)
 	}
 }
 
-/*
- * Returns the number of characters in the output buffer. This is
- * used in tty_wait_until_sent to wait until all characters have
- * appeared on the screen.
- */
-static int
-tty3270_chars_in_buffer(struct tty_struct *tty)
-{
-	return 0;
-}
-
 static void
 tty3270_flush_buffer(struct tty_struct *tty)
 {
@@ -1892,7 +1881,6 @@ static const struct tty_operations tty3270_ops = {
 	.put_char = tty3270_put_char,
 	.flush_chars = tty3270_flush_chars,
 	.write_room = tty3270_write_room,
-	.chars_in_buffer = tty3270_chars_in_buffer,
 	.flush_buffer = tty3270_flush_buffer,
 	.throttle = tty3270_throttle,
 	.unthrottle = tty3270_unthrottle,

drivers/tty/pty.c

@@ -143,19 +143,6 @@ static unsigned int pty_write_room(struct tty_struct *tty)
 	return tty_buffer_space_avail(tty->link->port);
 }
 
-/**
- *	pty_chars_in_buffer	-	characters currently in our tx queue
- *	@tty: our tty
- *
- *	Report how much we have in the transmit queue. As everything is
- *	instantly at the other end this is easy to implement.
- */
-
-static int pty_chars_in_buffer(struct tty_struct *tty)
-{
-	return 0;
-}
-
 /* Set the lock flag on a pty */
 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
 {
@@ -525,7 +512,6 @@ static const struct tty_operations master_pty_ops_bsd = {
 	.write = pty_write,
 	.write_room = pty_write_room,
 	.flush_buffer = pty_flush_buffer,
-	.chars_in_buffer = pty_chars_in_buffer,
 	.unthrottle = pty_unthrottle,
 	.ioctl = pty_bsd_ioctl,
 	.compat_ioctl = pty_bsd_compat_ioctl,
@@ -541,7 +527,6 @@ static const struct tty_operations slave_pty_ops_bsd = {
 	.write = pty_write,
 	.write_room = pty_write_room,
 	.flush_buffer = pty_flush_buffer,
-	.chars_in_buffer = pty_chars_in_buffer,
 	.unthrottle = pty_unthrottle,
 	.set_termios = pty_set_termios,
 	.cleanup = pty_cleanup,
@@ -776,7 +761,6 @@ static const struct tty_operations ptm_unix98_ops = {
 	.write = pty_write,
 	.write_room = pty_write_room,
 	.flush_buffer = pty_flush_buffer,
-	.chars_in_buffer = pty_chars_in_buffer,
 	.unthrottle = pty_unthrottle,
 	.ioctl = pty_unix98_ioctl,
 	.compat_ioctl = pty_unix98_compat_ioctl,
@@ -794,7 +778,6 @@ static const struct tty_operations pty_unix98_ops = {
 	.write = pty_write,
 	.write_room = pty_write_room,
 	.flush_buffer = pty_flush_buffer,
-	.chars_in_buffer = pty_chars_in_buffer,
 	.unthrottle = pty_unthrottle,
 	.set_termios = pty_set_termios,
 	.start = pty_start,

drivers/tty/vt/vt.c

@@ -3270,11 +3270,6 @@ static unsigned int con_write_room(struct tty_struct *tty)
 	return 32768;		/* No limit, really; we're not buffering */
 }
 
-static int con_chars_in_buffer(struct tty_struct *tty)
-{
-	return 0;		/* we're not buffering */
-}
-
 /*
  * con_throttle and con_unthrottle are only used for
  * paste_selection(), which has to stuff in a large number of
@@ -3521,7 +3516,6 @@ static const struct tty_operations con_ops = {
 	.write_room = con_write_room,
 	.put_char = con_put_char,
 	.flush_chars = con_flush_chars,
-	.chars_in_buffer = con_chars_in_buffer,
 	.ioctl = vt_ioctl,
 #ifdef CONFIG_COMPAT
 	.compat_ioctl = vt_compat_ioctl,