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>

arch/alpha/kernel/srmcons.c

@@ -142,7 +142,7 @@ srmcons_write(struct tty_struct *tty,
 	return count;
 }
 
-static int
+static unsigned int
 srmcons_write_room(struct tty_struct *tty)
 {
 	return 512;

arch/m68k/emu/nfcon.c

@@ -85,7 +85,7 @@ static int nfcon_tty_put_char(struct tty_struct *tty, unsigned char ch)
 	return 1;
 }
 
-static int nfcon_tty_write_room(struct tty_struct *tty)
+static unsigned int nfcon_tty_write_room(struct tty_struct *tty)
 {
 	return 64;
 }

arch/parisc/kernel/pdc_cons.c

@@ -103,7 +103,7 @@ static int pdc_console_tty_write(struct tty_struct *tty, const unsigned char *bu
 	return count;
 }
 
-static int pdc_console_tty_write_room(struct tty_struct *tty)
+static unsigned int pdc_console_tty_write_room(struct tty_struct *tty)
 {
 	return 32768; /* no limit, no buffer used */
 }

arch/um/drivers/line.c

@@ -32,7 +32,7 @@ static irqreturn_t line_interrupt(int irq, void *data)
  *
  * Should be called while holding line->lock (this does not modify data).
  */
-static int write_room(struct line *line)
+static unsigned int write_room(struct line *line)
 {
 	int n;
 
@@ -47,11 +47,11 @@ static int write_room(struct line *line)
 	return n - 1;
 }
 
-int line_write_room(struct tty_struct *tty)
+unsigned int line_write_room(struct tty_struct *tty)
 {
 	struct line *line = tty->driver_data;
 	unsigned long flags;
-	int room;
+	unsigned int room;
 
 	spin_lock_irqsave(&line->lock, flags);
 	room = write_room(line);

arch/um/drivers/line.h

@@ -70,7 +70,7 @@ extern void line_set_termios(struct tty_struct *tty, struct ktermios * old);
 extern int line_chars_in_buffer(struct tty_struct *tty);
 extern void line_flush_buffer(struct tty_struct *tty);
 extern void line_flush_chars(struct tty_struct *tty);
-extern int line_write_room(struct tty_struct *tty);
+extern unsigned int line_write_room(struct tty_struct *tty);
 extern void line_throttle(struct tty_struct *tty);
 extern void line_unthrottle(struct tty_struct *tty);
 

arch/xtensa/platforms/iss/console.c

@@ -100,7 +100,7 @@ static void rs_flush_chars(struct tty_struct *tty)
 {
 }
 
-static int rs_write_room(struct tty_struct *tty)
+static unsigned int rs_write_room(struct tty_struct *tty)
 {
 	/* Let's say iss can always accept 2K characters.. */
 	return 2 * 1024;

drivers/char/pcmcia/synclink_cs.c

@@ -1609,7 +1609,7 @@ cleanup:
 
 /* Return the count of free bytes in transmit buffer
  */
-static int mgslpc_write_room(struct tty_struct *tty)
+static unsigned int mgslpc_write_room(struct tty_struct *tty)
 {
 	MGSLPC_INFO *info = (MGSLPC_INFO *)tty->driver_data;
 	int ret;

drivers/char/ttyprintk.c

@@ -132,7 +132,7 @@ static int tpk_write(struct tty_struct *tty,
 /*
  * TTY operations write_room function.
  */
-static int tpk_write_room(struct tty_struct *tty)
+static unsigned int tpk_write_room(struct tty_struct *tty)
 {
 	return TPK_MAX_ROOM;
 }

drivers/ipack/devices/ipoctal.c

@@ -460,7 +460,7 @@ static int ipoctal_write_tty(struct tty_struct *tty,
 	return char_copied;
 }
 
-static int ipoctal_write_room(struct tty_struct *tty)
+static unsigned int ipoctal_write_room(struct tty_struct *tty)
 {
 	struct ipoctal_channel *channel = tty->driver_data;
 

drivers/isdn/capi/capi.c

@@ -1175,14 +1175,14 @@ static void capinc_tty_flush_chars(struct tty_struct *tty)
 	handle_minor_recv(mp);
 }
 
-static int capinc_tty_write_room(struct tty_struct *tty)
+static unsigned int capinc_tty_write_room(struct tty_struct *tty)
 {
 	struct capiminor *mp = tty->driver_data;
-	int room;
+	unsigned int room;
 
 	room = CAPINC_MAX_SENDQUEUE-skb_queue_len(&mp->outqueue);
 	room *= CAPI_MAX_BLKSIZE;
-	pr_debug("capinc_tty_write_room = %d\n", room);
+	pr_debug("capinc_tty_write_room = %u\n", room);
 	return room;
 }
 

drivers/misc/bcm-vk/bcm_vk_tty.c

@@ -214,7 +214,7 @@ static int bcm_vk_tty_write(struct tty_struct *tty,
 	return count;
 }
 
-static int bcm_vk_tty_write_room(struct tty_struct *tty)
+static unsigned int bcm_vk_tty_write_room(struct tty_struct *tty)
 {
 	struct bcm_vk *vk = dev_get_drvdata(tty->dev);
 

drivers/mmc/core/sdio_uart.c

@@ -797,7 +797,7 @@ static int sdio_uart_write(struct tty_struct *tty, const unsigned char *buf,
 	return ret;
 }
 
-static int sdio_uart_write_room(struct tty_struct *tty)
+static unsigned int sdio_uart_write_room(struct tty_struct *tty)
 {
 	struct sdio_uart_port *port = tty->driver_data;
 	return FIFO_SIZE - kfifo_len(&port->xmit_fifo);

drivers/net/usb/hso.c

@@ -1357,10 +1357,10 @@ out:
 }
 
 /* how much room is there for writing */
-static int hso_serial_write_room(struct tty_struct *tty)
+static unsigned int hso_serial_write_room(struct tty_struct *tty)
 {
 	struct hso_serial *serial = tty->driver_data;
-	int room;
+	unsigned int room;
 	unsigned long flags;
 
 	spin_lock_irqsave(&serial->serial_lock, flags);

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;
 

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;

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;

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;

drivers/staging/fwserial/fwserial.c

@@ -1113,16 +1113,16 @@ static int fwtty_write(struct tty_struct *tty, const unsigned char *buf, int c)
 	return (n < 0) ? 0 : n;
 }
 
-static int fwtty_write_room(struct tty_struct *tty)
+static unsigned int fwtty_write_room(struct tty_struct *tty)
 {
 	struct fwtty_port *port = tty->driver_data;
-	int n;
+	unsigned int n;
 
 	spin_lock_bh(&port->lock);
 	n = dma_fifo_avail(&port->tx_fifo);
 	spin_unlock_bh(&port->lock);
 
-	fwtty_dbg(port, "%d\n", n);
+	fwtty_dbg(port, "%u\n", n);
 
 	return n;
 }

drivers/staging/gdm724x/gdm_tty.c

@@ -183,7 +183,7 @@ static int gdm_tty_write(struct tty_struct *tty, const unsigned char *buf,
 	return len;
 }
 
-static int gdm_tty_write_room(struct tty_struct *tty)
+static unsigned int gdm_tty_write_room(struct tty_struct *tty)
 {
 	struct gdm *gdm = tty->driver_data;
 

drivers/staging/greybus/uart.c

@@ -440,7 +440,7 @@ static int gb_tty_write(struct tty_struct *tty, const unsigned char *buf,
 	return count;
 }
 
-static int gb_tty_write_room(struct tty_struct *tty)
+static unsigned int gb_tty_write_room(struct tty_struct *tty)
 {
 	struct gb_tty *gb_tty = tty->driver_data;
 	unsigned long flags;