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| author | Andrew Worsley <amworsley@gmail.com> | 2011-11-18 23:13:33 +1100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2011-11-26 09:08:38 -0800 |
| commit | 4c72dfff8cfbc0d5c63145691c9dbbd1df995c1c (patch) | |
| tree | 982fbeadceb355e6552f383fa8aaaafb1458e264 | |
| parent | 22e88b06a5779026f242c2eb628ec058c79b2ed0 (diff) | |
| download | lwn-4c72dfff8cfbc0d5c63145691c9dbbd1df995c1c.tar.gz lwn-4c72dfff8cfbc0d5c63145691c9dbbd1df995c1c.zip | |
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.c | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c index f34f6ed0faff..e16394c9dbd4 100644 --- a/drivers/usb/serial/ftdi_sio.c +++ b/drivers/usb/serial/ftdi_sio.c @@ -2083,13 +2083,19 @@ 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; @@ -2130,6 +2136,7 @@ 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), @@ -2157,6 +2164,7 @@ 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, |