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authorAndrew Worsley <amworsley@gmail.com>2011-11-18 23:13:33 +1100
committerGreg Kroah-Hartman <gregkh@suse.de>2011-11-26 09:10:37 -0800
commit552f6bf1bb0eda0011c0525dd587aa9e7ba5b846 (patch)
tree095653dd80d0ab356d8c8a226386f6fbe30108f6
parent4ea27e18d645d3706675bb4d49330ffe867dd487 (diff)
USB: Fix Corruption issue in USB ftdi driver ftdi_sio.c
commit b1ffb4c851f185e9051ba837c16d9b84ef688d26 upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--drivers/usb/serial/ftdi_sio.c14
1 files changed, 11 insertions, 3 deletions
diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 7a4b41c30162..5689b903256f 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -2355,13 +2355,19 @@ 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 */
termios->c_cflag &= ~CMSPAR;
@@ -2398,6 +2404,7 @@ static void ftdi_set_termios(struct tty_struct *tty,
}
/* Now do the baudrate */
+no_data_parity_stop_changes:
if ((cflag & CBAUD) == B0) {
/* Disable flow control */
if (usb_control_msg(dev, usb_sndctrlpipe(dev, 0),
@@ -2423,6 +2430,7 @@ static void ftdi_set_termios(struct tty_struct *tty,
/* Set flow control */
/* Note device also supports DTR/CD (ugh) and Xon/Xoff in hardware */
+no_c_cflag_changes:
if (cflag & CRTSCTS) {
dbg("%s Setting to CRTSCTS flow control", __func__);
if (usb_control_msg(dev,