n_tty: move lnext handling

Move lnext handling from __receive_buf to n_tty_receive_buf_standard. It
simplifies the handling as it needs not fetching 'flag' and decrement
'count' in __receive_buf. Instead, all this is left up to the loop in
n_tty_receive_buf_standard which already does that.

This way, no need to repeat the action when n_tty_receive_char_special
returns true -- ldata->lnext is set there in that case, so the 'if
(ldata->lnext)' check is sufficient. The next patch will switch
n_tty_receive_char_special to return 'void'.

The result is much simplified code flow.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210505091928.22010-7-jslaby@suse.czSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/n_tty.c

@@ -1538,6 +1538,12 @@ static void n_tty_receive_buf_standard(struct tty_struct *tty,
 	while (count--) {
 		if (fp)
 			flag = *fp++;
+
+		if (ldata->lnext) {
+			n_tty_receive_char_lnext(tty, *cp++, flag);
+			continue;
+		}
+
 		if (likely(flag == TTY_NORMAL)) {
 			unsigned char c = *cp++;
 
@@ -1551,12 +1557,8 @@ static void n_tty_receive_buf_standard(struct tty_struct *tty,
 			}
 			if (!test_bit(c, ldata->char_map))
 				n_tty_receive_char(tty, c);
-			else if (n_tty_receive_char_special(tty, c) && count) {
-				if (fp)
-					flag = *fp++;
-				n_tty_receive_char_lnext(tty, *cp++, flag);
-				count--;
-			}
+			else
+				n_tty_receive_char_special(tty, c);
 		} else
 			n_tty_receive_char_flagged(tty, *cp++, flag);
 	}
@@ -1575,15 +1577,6 @@ static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
 	else if (tty->closing && !L_EXTPROC(tty))
 		n_tty_receive_buf_closing(tty, cp, fp, count);
 	else {
-		if (ldata->lnext) {
-			char flag = TTY_NORMAL;
-
-			if (fp)
-				flag = *fp++;
-			n_tty_receive_char_lnext(tty, *cp++, flag);
-			count--;
-		}
-
 		n_tty_receive_buf_standard(tty, cp, fp, count);
 
 		flush_echoes(tty);