linux-kernel - [PATCH 3.2 139/152] s390/3215: fix tty output containing tabs

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Message-ID: <lsq.1424137613.159377267@decadent.org.uk>
Date:	Tue, 17 Feb 2015 01:46:53 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Stephen Powell" <zlinuxman@...way.com>,
	"Martin Schwidefsky" <schwidefsky@...ibm.com>
Subject: [PATCH 3.2 139/152] s390/3215: fix tty output containing tabs

3.2.67-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Martin Schwidefsky <schwidefsky@...ibm.com>

commit e512d56c799517f33b301d81e9a5e0ebf30c2d1e upstream.

git commit 37f81fa1f63ad38e16125526bb2769ae0ea8d332
"n_tty: do O_ONLCR translation as a single write"
surfaced a bug in the 3215 device driver. In combination this
broke tab expansion for tty ouput.

The cause is an asymmetry in the behaviour of tty3215_ops->write
vs tty3215_ops->put_char. The put_char function scans for '\t'
but the write function does not.

As the driver has logic for the '\t' expansion remove XTABS
from c_oflag of the initial termios as well.

Reported-by: Stephen Powell <zlinuxman@...way.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/s390/char/con3215.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

--- a/drivers/s390/char/con3215.c
+++ b/drivers/s390/char/con3215.c
@@ -993,12 +993,26 @@ static int tty3215_write(struct tty_stru
 			 const unsigned char *buf, int count)
 {
 	struct raw3215_info *raw;
+	int i, written;
 
 	if (!tty)
 		return 0;
 	raw = (struct raw3215_info *) tty->driver_data;
-	raw3215_write(raw, buf, count);
-	return count;
+	written = count;
+	while (count > 0) {
+		for (i = 0; i < count; i++)
+			if (buf[i] == '\t' || buf[i] == '\n')
+				break;
+		raw3215_write(raw, buf, i);
+		count -= i;
+		buf += i;
+		if (count > 0) {
+			raw3215_putchar(raw, *buf);
+			count--;
+			buf++;
+		}
+	}
+	return written;
 }
 
 /*
@@ -1146,7 +1160,7 @@ static int __init tty3215_init(void)
 	driver->subtype = SYSTEM_TYPE_TTY;
 	driver->init_termios = tty_std_termios;
 	driver->init_termios.c_iflag = IGNBRK | IGNPAR;
-	driver->init_termios.c_oflag = ONLCR | XTABS;
+	driver->init_termios.c_oflag = ONLCR;
 	driver->init_termios.c_lflag = ISIG;
 	driver->flags = TTY_DRIVER_REAL_RAW;
 	tty_set_operations(driver, &tty3215_ops);

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