diff options
| author | Colin Leitner <colin.leitner@googlemail.com> | 2014-01-06 21:33:54 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-01-07 16:28:43 -0800 |
| commit | c1f15196ac3b541d084dc80a8fbd8a74c6a0bd44 (patch) | |
| tree | 95af331f275796dc541045fae1ef00757bd40503 /drivers/usb/serial | |
| parent | 30666249eae3b04875d514dea557d1ab1468c006 (diff) | |
USB: ftdi_sio: added CS5 quirk for broken smartcard readers
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.
Cc: stable <stable@vger.kernel.org>
Reported-by: Heinrich Siebmanns <H.Siebmanns@t-online.de>
Tested-by: Heinrich Siebmanns <H.Siebmanns@t-online.de>
Signed-off-by: Colin Leitner <colin.leitner@gmail.com>
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb/serial')
| -rw-r--r-- | drivers/usb/serial/ftdi_sio.c | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c index a4bebacc5cae..5057201bbba8 100644 --- a/drivers/usb/serial/ftdi_sio.c +++ b/drivers/usb/serial/ftdi_sio.c @@ -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. + * + * 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; @@ -2171,6 +2181,9 @@ 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"); |