tty: tty_buffer: switch insert functions to size_t

All the functions accept size_t as a size argument. They finally return
the same size (or less). It is quite unexpected that they return a
signed value and can confuse users to check for negative values.

Instead, return the same size_t as accepted to make clear we return
values >= 0, where zero in fact means failure.

Signed-off-by: "Jiri Slaby (SUSE)" <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/tty_buffer.c

···
 }
 EXPORT_SYMBOL_GPL(tty_buffer_request_room);
 
-int __tty_insert_flip_string_flags(struct tty_port *port, const u8 *chars,
-				   const u8 *flags, bool mutable_flags,
-				   size_t size)
+size_t __tty_insert_flip_string_flags(struct tty_port *port, const u8 *chars,
+				      const u8 *flags, bool mutable_flags,
+				      size_t size)
 {
 	bool need_flags = mutable_flags || flags[0] != TTY_NORMAL;
-	int copied = 0;
+	size_t copied = 0;
 
 	do {
-		int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
-		int space = __tty_buffer_request_room(port, goal, need_flags);
+		size_t goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
+		size_t space = __tty_buffer_request_room(port, goal, need_flags);
 		struct tty_buffer *tb = port->buf.tail;
 
 		if (unlikely(space == 0))

include/linux/tty_flip.h

···
 int tty_buffer_set_limit(struct tty_port *port, int limit);
 unsigned int tty_buffer_space_avail(struct tty_port *port);
 int tty_buffer_request_room(struct tty_port *port, size_t size);
-int __tty_insert_flip_string_flags(struct tty_port *port, const u8 *chars,
-				   const u8 *flags, bool mutable_flags,
-				   size_t size);
+size_t __tty_insert_flip_string_flags(struct tty_port *port, const u8 *chars,
+				      const u8 *flags, bool mutable_flags,
+				      size_t size);
 int tty_prepare_flip_string(struct tty_port *port, u8 **chars, size_t size);
 void tty_flip_buffer_push(struct tty_port *port);
 int __tty_insert_flip_char(struct tty_port *port, u8 ch, u8 flag);
···
  *
  * Returns: the number added.
  */
-static inline int tty_insert_flip_string_fixed_flag(struct tty_port *port,
-						    const u8 *chars, u8 flag,
-						    size_t size)
+static inline size_t tty_insert_flip_string_fixed_flag(struct tty_port *port,
+						       const u8 *chars, u8 flag,
+						       size_t size)
 {
 	return __tty_insert_flip_string_flags(port, chars, &flag, false, size);
 }
···
  *
  * Returns: the number added.
  */
-static inline int tty_insert_flip_string_flags(struct tty_port *port,
-					       const u8 *chars, const u8 *flags,
-					       size_t size)
+static inline size_t tty_insert_flip_string_flags(struct tty_port *port,
+						  const u8 *chars,
+						  const u8 *flags, size_t size)
 {
 	return __tty_insert_flip_string_flags(port, chars, flags, true, size);
 }
 
 
-static inline int tty_insert_flip_char(struct tty_port *port, u8 ch, u8 flag)
+static inline size_t tty_insert_flip_char(struct tty_port *port, u8 ch, u8 flag)
 {
 	struct tty_buffer *tb = port->buf.tail;
 	int change;
···
 	return __tty_insert_flip_char(port, ch, flag);
 }
 
-static inline int tty_insert_flip_string(struct tty_port *port,
-		const u8 *chars, size_t size)
+static inline size_t tty_insert_flip_string(struct tty_port *port,
+					    const u8 *chars, size_t size)
 {
 	return tty_insert_flip_string_fixed_flag(port, chars, TTY_NORMAL, size);
 }