diff options
| author | Colin Leitner <colin.leitner@googlemail.com> | 2014-01-06 21:33:54 +0100 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2014-04-02 00:58:41 +0100 |
| commit | 9e397d2a211c54ef195f39786ea5986db4ef20dd (patch) | |
| tree | 590573ea41fc38b5af9c0f417851a45cb233a6fa /drivers/usb/serial | |
| parent | 2b5e579e01252cd65b073360eec69042ea77affc (diff) | |
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@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>
[bwh: Backported to 3.2: s/ddev/\&port->dev/]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
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 85504bb130a..8321a9f3d41 100644 --- a/drivers/usb/serial/ftdi_sio.c +++ b/drivers/usb/serial/ftdi_sio.c @@ -2193,10 +2193,20 @@ 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(&port->dev, "requested CSIZE setting not supported\n"); termios->c_cflag &= ~CSIZE; @@ -2243,6 +2253,9 @@ no_skip: urb_value |= FTDI_SIO_SET_DATA_PARITY_NONE; } switch (cflag & CSIZE) { + case CS5: + dev_dbg(&port->dev, "Setting CS5 quirk\n"); + break; case CS7: urb_value |= 7; dev_dbg(&port->dev, "Setting CS7\n"); |