Commit c1f15196 authored by Colin Leitner's avatar Colin Leitner Committed by Greg Kroah-Hartman

USB: ftdi_sio: added CS5 quirk for broken smartcard readers

Genuine FTDI chips support only CS7/8. A previous fix in commit
8704211f ("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.

Cc: stable <stable@vger.kernel.org>
Reported-by: default avatarHeinrich Siebmanns <H.Siebmanns@t-online.de>
Tested-by: default avatarHeinrich Siebmanns <H.Siebmanns@t-online.de>
Signed-off-by: default avatarColin Leitner <colin.leitner@gmail.com>
Signed-off-by: default avatarJohan Hovold <jhovold@gmail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 30666249
...@@ -2121,10 +2121,20 @@ static void ftdi_set_termios(struct tty_struct *tty, ...@@ -2121,10 +2121,20 @@ 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. * 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"); dev_warn(ddev, "requested CSIZE setting not supported\n");
termios->c_cflag &= ~CSIZE; termios->c_cflag &= ~CSIZE;
...@@ -2171,6 +2181,9 @@ static void ftdi_set_termios(struct tty_struct *tty, ...@@ -2171,6 +2181,9 @@ static void ftdi_set_termios(struct tty_struct *tty,
urb_value |= FTDI_SIO_SET_DATA_PARITY_NONE; urb_value |= FTDI_SIO_SET_DATA_PARITY_NONE;
} }
switch (cflag & CSIZE) { switch (cflag & CSIZE) {
case CS5:
dev_dbg(ddev, "Setting CS5 quirk\n");
break;
case CS7: case CS7:
urb_value |= 7; urb_value |= 7;
dev_dbg(ddev, "Setting CS7\n"); dev_dbg(ddev, "Setting CS7\n");
......
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