tty: make tty_operations::write_room return uint

Line disciplines expect a positive value or zero returned from
tty->ops->write_room (invoked by tty_write_room). So make this
assumption explicit by using unsigned int as a return value. Both of
tty->ops->write_room and tty_write_room.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Acked-by: Alex Elder <elder@linaro.org>
Acked-by: Max Filippov <jcmvbkbc@gmail.com> # xtensa
Acked-by: David Sterba <dsterba@suse.com>
Acked-By: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Richard Henderson <rth@twiddle.net>
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: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Chris Zankel <chris@zankel.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Cc: Jens Taprogge <jens.taprogge@taprogge.org>
Cc: Karsten Keil <isdn@linux-pingi.de>
Cc: Scott Branden <scott.branden@broadcom.com>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: David Lin <dtwlin@gmail.com>
Cc: Johan Hovold <johan@kernel.org>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Oliver Neukum <oneukum@suse.com>
Cc: Felipe Balbi <balbi@kernel.org>
Cc: Mathias Nyman <mathias.nyman@intel.com>
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>
Cc: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Link: https://lore.kernel.org/r/20210505091928.22010-23-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

4 files changed, 6 insertions, 6 deletions

diff --git a/drivers/s390/char/con3215.c b/drivers/s390/char/con3215.c
index 1fd5bca9fa20..c9fd4a05931a 100644
--- a/drivers/s390/char/con3215.c
+++ b/drivers/s390/char/con3215.c
@@ -924,7 +924,7 @@ static void tty3215_close(struct tty_struct *tty, struct file * filp)
 /*
  * Returns the amount of free space in the output buffer.
  */
-static int tty3215_write_room(struct tty_struct *tty)
+static unsigned int tty3215_write_room(struct tty_struct *tty)
 {
 	struct raw3215_info *raw = tty->driver_data;
 
diff --git a/drivers/s390/char/sclp_tty.c b/drivers/s390/char/sclp_tty.c
index 4456ceb23bd2..ea1e43fd16bc 100644
--- a/drivers/s390/char/sclp_tty.c
+++ b/drivers/s390/char/sclp_tty.c
@@ -86,12 +86,12 @@ sclp_tty_close(struct tty_struct *tty, struct file *filp)
  * a string of newlines. Every newline creates a new message which
  * needs 82 bytes.
  */
-static int
+static unsigned int
 sclp_tty_write_room (struct tty_struct *tty)
 {
 	unsigned long flags;
 	struct list_head *l;
-	int count;
+	unsigned int count;
 
 	spin_lock_irqsave(&sclp_tty_lock, flags);
 	count = 0;
diff --git a/drivers/s390/char/sclp_vt220.c b/drivers/s390/char/sclp_vt220.c
index 7f4445b0f819..b621adee35f0 100644
--- a/drivers/s390/char/sclp_vt220.c
+++ b/drivers/s390/char/sclp_vt220.c
@@ -609,12 +609,12 @@ sclp_vt220_flush_chars(struct tty_struct *tty)
  * to change as output buffers get emptied, or if the output flow
  * control is acted.
  */
-static int
+static unsigned int
 sclp_vt220_write_room(struct tty_struct *tty)
 {
 	unsigned long flags;
 	struct list_head *l;
-	int count;
+	unsigned int count;
 
 	spin_lock_irqsave(&sclp_vt220_lock, flags);
 	count = 0;
diff --git a/drivers/s390/char/tty3270.c b/drivers/s390/char/tty3270.c
index 1b68564799fa..82d4c961ed06 100644
--- a/drivers/s390/char/tty3270.c
+++ b/drivers/s390/char/tty3270.c
@@ -1071,7 +1071,7 @@ static void tty3270_cleanup(struct tty_struct *tty)
 /*
  * We always have room.
  */
-static int
+static unsigned int
 tty3270_write_room(struct tty_struct *tty)
 {
 	return INT_MAX;