From 2eee28818de1ac5e0b2756b84eb2fc9ae6679b6e Mon Sep 17 00:00:00 2001 From: Johan Hovold Date: Thu, 2 Feb 2017 17:38:35 +0100 Subject: USB: serial: ftdi_sio: fix line-status over-reporting commit a6bb1e17a39818b01b55d8e6238b4b5f06d55038 upstream. FTDI devices use a receive latency timer to periodically empty the receive buffer and report modem and line status (also when the buffer is empty). When a break or error condition is detected the corresponding status flags will be set on a packet with nonzero data payload and the flags are not updated until the break is over or further characters are received. In order to avoid over-reporting break and error conditions, these flags must therefore only be processed for packets with payload. This specifically fixes the case where after an overrun, the error condition is continuously reported and NULL-characters inserted until further data is received. Reported-by: Michael Walle Fixes: 72fda3ca6fc1 ("USB: serial: ftd_sio: implement sysrq handling on break") Fixes: 166ceb690750 ("USB: ftdi_sio: clean up line-status handling") Signed-off-by: Johan Hovold Signed-off-by: Ben Hutchings --- drivers/usb/serial/ftdi_sio.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) (limited to 'drivers') diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c index bbd1918b72dc..56f88df5906b 100644 --- a/drivers/usb/serial/ftdi_sio.c +++ b/drivers/usb/serial/ftdi_sio.c @@ -2109,6 +2109,20 @@ static int ftdi_process_packet(struct usb_serial_port *port, priv->prev_status = status; } + /* save if the transmitter is empty or not */ + if (packet[1] & FTDI_RS_TEMT) + priv->transmit_empty = 1; + else + priv->transmit_empty = 0; + + len -= 2; + if (!len) + return 0; /* status only */ + + /* + * Break and error status must only be processed for packets with + * data payload to avoid over-reporting. + */ flag = TTY_NORMAL; if (packet[1] & FTDI_RS_ERR_MASK) { /* Break takes precedence over parity, which takes precedence @@ -2131,15 +2145,6 @@ static int ftdi_process_packet(struct usb_serial_port *port, } } - /* save if the transmitter is empty or not */ - if (packet[1] & FTDI_RS_TEMT) - priv->transmit_empty = 1; - else - priv->transmit_empty = 0; - - len -= 2; - if (!len) - return 0; /* status only */ port->icount.rx += len; ch = packet + 2; -- cgit v1.2.3