path: root/drivers/usb/serial
diff options
authorAndrew Worsley <amworsley@gmail.com>2011-11-18 23:13:33 +1100
committerGreg Kroah-Hartman <gregkh@suse.de>2011-11-18 11:27:16 -0800
commitb1ffb4c851f185e9051ba837c16d9b84ef688d26 (patch)
tree393552d83086b527a641425ef1634b76b8767585 /drivers/usb/serial
parent4aa3648c719265bac9c2742c9ebb043e6dbdd790 (diff)
USB: Fix Corruption issue in USB ftdi driver ftdi_sio.c
Fix for ftdi_set_termios() glitching output ftdi_set_termios() is constantly setting the baud rate, data bits and parity unnecessarily on every call, . When called while characters are being transmitted can cause the FTDI chip to corrupt the serial port bit stream output by stalling the output half a bit during the output of a character. Simple fix by skipping this setting if the baud rate/data bits/parity are unchanged. Signed-off-by: Andrew Worsley <amworsley@gmail.com> Cc: stable <stable@vger.kernel.org> ---- I had a brief run with strace on the getty and it was doing ioctl()s on each call but it didn't look relavant to the problem. I think the issue is that XON/XOFF flow control was being implmented via hardware - for the ixoff to allow the user to use XON/XOFF to control output. Unfortunately it would send 3 Control URBs updating all of the settings after each piece of input I am trying to work around the issue of gmail messing with the tab/spacing by submitting via SMTP via gmail which I believe should fix the issue. The patch is against v3.2-rc2 and compiles - but no additional testing in this kernel has been done. Thanks Andrew Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/usb/serial')
1 files changed, 11 insertions, 3 deletions
diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 8fe034d2d3e..bd4298bb675 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -2104,13 +2104,19 @@ static void ftdi_set_termios(struct tty_struct *tty,
cflag = termios->c_cflag;
- /* FIXME -For this cut I don't care if the line is really changing or
- not - so just do the change regardless - should be able to
- compare old_termios and tty->termios */
+ if (old_termios->c_cflag == termios->c_cflag
+ && old_termios->c_ispeed == termios->c_ispeed
+ && old_termios->c_ospeed == termios->c_ospeed)
+ goto no_c_cflag_changes;
/* NOTE These routines can get interrupted by
ftdi_sio_read_bulk_callback - need to examine what this means -
don't see any problems yet */
+ if ((old_termios->c_cflag & (CSIZE|PARODD|PARENB|CMSPAR|CSTOPB)) ==
+ (termios->c_cflag & (CSIZE|PARODD|PARENB|CMSPAR|CSTOPB)))
+ goto no_data_parity_stop_changes;
/* Set number of data bits, parity, stop bits */
urb_value = 0;
@@ -2151,6 +2157,7 @@ static void ftdi_set_termios(struct tty_struct *tty,
/* Now do the baudrate */
if ((cflag & CBAUD) == B0) {
/* Disable flow control */
if (usb_control_msg(dev, usb_sndctrlpipe(dev, 0),
@@ -2178,6 +2185,7 @@ static void ftdi_set_termios(struct tty_struct *tty,
/* Set flow control */
/* Note device also supports DTR/CD (ugh) and Xon/Xoff in hardware */
if (cflag & CRTSCTS) {
dbg("%s Setting to CRTSCTS flow control", __func__);
if (usb_control_msg(dev,