[3.8.y.z extended stable] Patch "USB: ftdi_sio: added CS5 quirk for broken smartcard readers" has been added to staging queue

[Kamal Mostafa]

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

    USB: ftdi_sio: added CS5 quirk for broken smartcard readers

to the linux-3.8.y-queue branch of the 3.8.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-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.18.

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

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 214b63b7607d604a0c50e465741a13a304d2ca0e Mon Sep 17 00:00:00 2001
From: Colin Leitner <colin.leitner at googlemail.com>
Date: Mon, 6 Jan 2014 21:33:54 +0100
Subject: USB: ftdi_sio: added CS5 quirk for broken smartcard readers

commit c1f15196ac3b541d084dc80a8fbd8a74c6a0bd44 upstream.

Genuine FTDI chips support only CS7/8. A previous fix in commit
8704211f65a2 ("USB: ftdi_sio: fixed handling of unsupported CSIZE
setting") enforced this limitation and reported it back to userspace.

However, certain types of smartcard readers depend on specific
driver behaviour that requests 0 data bits (not 5) to change into a
different operating mode if CS5 has been set.

This patch reenables this behaviour for all FTDI devices.

Tagged to be added to stable, because it affects a lot of users of
embedded systems which rely on these readers to work properly.

Reported-by: Heinrich Siebmanns <H.Siebmanns at t-online.de>
Tested-by: Heinrich Siebmanns <H.Siebmanns at t-online.de>
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: Kamal Mostafa <kamal at canonical.com>
---
 drivers/usb/serial/ftdi_sio.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index ede7f9f..8856967 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -2181,10 +2181,20 @@ static void ftdi_set_termios(struct tty_struct *tty,
 	}

 	/*
-	 * All FTDI UART chips are limited to CS7/8. We won't pretend to
+	 * All FTDI UART chips are limited to CS7/8. We shouldn't pretend to
 	 * support CS5/6 and revert the CSIZE setting instead.
+	 *
+	 * CS5 however is used to control some smartcard readers which abuse
+	 * this limitation to switch modes. Original FTDI chips fall back to
+	 * eight data bits.
+	 *
+	 * TODO: Implement a quirk to only allow this with mentioned
+	 *       readers. One I know of (Argolis Smartreader V1)
+	 *       returns "USB smartcard server" as iInterface string.
+	 *       The vendor didn't bother with a custom VID/PID of
+	 *       course.
 	 */
-	if ((C_CSIZE(tty) != CS8) && (C_CSIZE(tty) != CS7)) {
+	if (C_CSIZE(tty) == CS6) {
 		dev_warn(ddev, "requested CSIZE setting not supported\n");

 		termios->c_cflag &= ~CSIZE;
@@ -2231,6 +2241,9 @@ no_skip:
 		urb_value |= FTDI_SIO_SET_DATA_PARITY_NONE;
 	}
 	switch (cflag & CSIZE) {
+	case CS5:
+		dev_dbg(ddev, "Setting CS5 quirk\n");
+		break;
 	case CS7:
 		urb_value |= 7;
 		dev_dbg(ddev, "Setting CS7\n");
--
1.8.3.2