[3.11.y.z extended stable] Patch "USB: ftdi_sio: fixed handling of unsupported CSIZE setting" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    USB: ftdi_sio: fixed handling of unsupported CSIZE setting

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 29cbbd9dbf2d6e59611fbc89d19c60d44738c9f7 Mon Sep 17 00:00:00 2001
From: Colin Leitner <colin.leitner at googlemail.com>
Date: Tue, 5 Nov 2013 18:02:34 +0100
Subject: USB: ftdi_sio: fixed handling of unsupported CSIZE setting

commit 8704211f65a2106ba01b6ac9727cdaf9ca11594c upstream.

FTDI UARTs support only 7 or 8 data bits. Until now the ftdi_sio driver would
only report this limitation for CS6 to dmesg and fail to reflect this fact to
tcgetattr.

This patch reverts the unsupported CSIZE setting and reports the fact with less
severance to dmesg for both CS5 and CS6.

To test the patch it's sufficient to call

    stty -F /dev/ttyUSB0 cs5

which will succeed without the patch and report an error with the patch
applied.

As an additional fix this patch ensures that the control request will always
include a data bit size.

Signed-off-by: Colin Leitner <colin.leitner at gmail.com>
Signed-off-by: Johan Hovold <jhovold at gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/usb/serial/ftdi_sio.c | 37 ++++++++++++++++++++++++-------------
 1 file changed, 24 insertions(+), 13 deletions(-)

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index aa3aed5..92549cc 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -2131,6 +2131,20 @@ static void ftdi_set_termios(struct tty_struct *tty,
 		termios->c_cflag |= CRTSCTS;
 	}

+	/*
+	 * All FTDI UART chips are limited to CS7/8. We won't pretend to
+	 * support CS5/6 and revert the CSIZE setting instead.
+	 */
+	if ((C_CSIZE(tty) != CS8) && (C_CSIZE(tty) != CS7)) {
+		dev_warn(ddev, "requested CSIZE setting not supported\n");
+
+		termios->c_cflag &= ~CSIZE;
+		if (old_termios)
+			termios->c_cflag |= old_termios->c_cflag & CSIZE;
+		else
+			termios->c_cflag |= CS8;
+	}
+
 	cflag = termios->c_cflag;

 	if (!old_termios)
@@ -2167,19 +2181,16 @@ no_skip:
 	} else {
 		urb_value |= FTDI_SIO_SET_DATA_PARITY_NONE;
 	}
-	if (cflag & CSIZE) {
-		switch (cflag & CSIZE) {
-		case CS7:
-			urb_value |= 7;
-			dev_dbg(ddev, "Setting CS7\n");
-			break;
-		case CS8:
-			urb_value |= 8;
-			dev_dbg(ddev, "Setting CS8\n");
-			break;
-		default:
-			dev_err(ddev, "CSIZE was set but not CS7-CS8\n");
-		}
+	switch (cflag & CSIZE) {
+	case CS7:
+		urb_value |= 7;
+		dev_dbg(ddev, "Setting CS7\n");
+		break;
+	default:
+	case CS8:
+		urb_value |= 8;
+		dev_dbg(ddev, "Setting CS8\n");
+		break;
 	}

 	/* This is needed by the break command since it uses the same command
--
1.8.3.2