serial: serial_core: simplify uart_ioctl() returns

Neither uart_do_autoconfig(), nor uart_wait_modem_status() can return
-ENOIOCTLCMD. The ENOIOCTLCMD checks are there to check if 'cmd' matched
against TIOCSERCONFIG, and TIOCMIWAIT respectively. (With 0 or error in
'ret', it does not matter.)

Therefore, the code can simply return from the TIOCSERCONFIG and
TIOCMIWAIT spots immediately.

To be more explicit, use 'if' instead of switch-case for those single
values.

And return without jumping to the 'out' label -- it can be removed too.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Link: https://patch.msgid.link/20251119100140.830761-10-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Jiri Slaby (SUSE)

drivers/tty/serial/serial_core.c

@@ -1560,37 +1560,20 @@ uart_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
 	void __user *uarg = (void __user *)arg;
 	int ret = -ENOIOCTLCMD;
 
-
-	/*
-	 * These ioctls don't rely on the hardware to be present.
-	 */
-	switch (cmd) {
-	case TIOCSERCONFIG:
+	/* This ioctl doesn't rely on the hardware to be present. */
+	if (cmd == TIOCSERCONFIG) {
 		down_write(&tty->termios_rwsem);
 		ret = uart_do_autoconfig(tty, state);
 		up_write(&tty->termios_rwsem);
-		break;
-	}
-
-	if (ret != -ENOIOCTLCMD)
-		goto out;
-
-	if (tty_io_error(tty)) {
-		ret = -EIO;
-		goto out;
+		return ret;
 	}
 
-	/*
-	 * The following should only be used when hardware is present.
-	 */
-	switch (cmd) {
-	case TIOCMIWAIT:
-		ret = uart_wait_modem_status(state, arg);
-		break;
-	}
+	if (tty_io_error(tty))
+		return -EIO;
 
-	if (ret != -ENOIOCTLCMD)
-		goto out;
+	/* This should only be used when the hardware is present. */
+	if (cmd == TIOCMIWAIT)
+		return uart_wait_modem_status(state, arg);
 
 	/* rs485_config requires more locking than others */
 	if (cmd == TIOCSRS485)
@@ -1638,7 +1621,7 @@ uart_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
 	mutex_unlock(&port->mutex);
 	if (cmd == TIOCSRS485)
 		up_write(&tty->termios_rwsem);
-out:
+
 	return ret;
 }