USB: serial: ftdi_sio: clean up flow control management

Clean up the somewhat convoluted hardware-assisted flow control
handling.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

1 files changed, 23 insertions, 58 deletions

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 3d7f181e7e2a..b5cef322826f 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -2191,12 +2191,8 @@ static void ftdi_set_termios(struct tty_struct *tty,
         struct ftdi_private *priv = usb_get_serial_port_data(port);
         struct ktermios *termios = &tty->termios;
         unsigned int cflag = termios->c_cflag;
-        u16 value;
-
-        /* Added for xon/xoff support */
-        unsigned int iflag = termios->c_iflag;
-        unsigned char vstop;
-        unsigned char vstart;
+        u16 value, index;
+        int ret;
 
         /* Force baud rate if this device requires it, unless it is set to
            B0. */
@@ -2325,61 +2321,30 @@ no_data_parity_stop_changes:
                         set_mctrl(port, TIOCM_DTR | TIOCM_RTS);
         }
 
-        /* Set flow control */
-        /* Note device also supports DTR/CD (ugh) and Xon/Xoff in hardware */
 no_c_cflag_changes:
-        if (cflag & CRTSCTS) {
-                dev_dbg(ddev, "%s Setting to CRTSCTS flow control\n", __func__);
-                if (usb_control_msg(dev,
-                                    usb_sndctrlpipe(dev, 0),
-                                    FTDI_SIO_SET_FLOW_CTRL_REQUEST,
-                                    FTDI_SIO_SET_FLOW_CTRL_REQUEST_TYPE,
-                                    0 , (FTDI_SIO_RTS_CTS_HS | priv->interface),
-                                    NULL, 0, WDR_TIMEOUT) < 0) {
-                        dev_err(ddev, "urb failed to set to rts/cts flow control\n");
-                }
+        /* Set hardware-assisted flow control */
+        value = 0;
+
+        if (C_CRTSCTS(tty)) {
+                dev_dbg(&port->dev, "enabling rts/cts flow control\n");
+                index = FTDI_SIO_RTS_CTS_HS;
+        } else if (I_IXON(tty)) {
+                dev_dbg(&port->dev, "enabling xon/xoff flow control\n");
+                index = FTDI_SIO_XON_XOFF_HS;
+                value = STOP_CHAR(tty) << 8 | START_CHAR(tty);
         } else {
-                /*
-                 * Xon/Xoff code
-                 */
-                if (iflag & IXON) {
-                        dev_dbg(ddev, "%s  request to enable xonxoff iflag=%04x\n",
-                                __func__, iflag);
-                        /* Try to enable the XON/XOFF on the ftdi_sio
-                         * Set the vstart and vstop -- could have been done up
-                         * above where a lot of other dereferencing is done but
-                         * that would be very inefficient as vstart and vstop
-                         * are not always needed.
-                         */
-                        vstart = termios->c_cc[VSTART];
-                        vstop = termios->c_cc[VSTOP];
-                        value = (vstop << 8) | (vstart);
-
-                        if (usb_control_msg(dev,
-                                            usb_sndctrlpipe(dev, 0),
-                                            FTDI_SIO_SET_FLOW_CTRL_REQUEST,
-                                            FTDI_SIO_SET_FLOW_CTRL_REQUEST_TYPE,
-                                            value , (FTDI_SIO_XON_XOFF_HS
-                                                         | priv->interface),
-                                            NULL, 0, WDR_TIMEOUT) < 0) {
-                                dev_err(&port->dev, "urb failed to set to "
-                                        "xon/xoff flow control\n");
-                        }
-                } else {
-                        /* else clause to only run if cflag ! CRTSCTS and iflag
-                         * ! XON. CHECKME Assuming XON/XOFF handled by tty
-                         * stack - not by device */
-                        dev_dbg(ddev, "%s Turning off hardware flow control\n", __func__);
-                        if (usb_control_msg(dev,
-                                            usb_sndctrlpipe(dev, 0),
-                                            FTDI_SIO_SET_FLOW_CTRL_REQUEST,
-                                            FTDI_SIO_SET_FLOW_CTRL_REQUEST_TYPE,
-                                            0, priv->interface,
-                                            NULL, 0, WDR_TIMEOUT) < 0) {
-                                dev_err(ddev, "urb failed to clear flow control\n");
-                        }
-                }
+                dev_dbg(&port->dev, "disabling flow control\n");
+                index = FTDI_SIO_DISABLE_FLOW_CTRL;
         }
+
+        index |= priv->interface;
+
+        ret = usb_control_msg(dev, usb_sndctrlpipe(dev, 0),
+                        FTDI_SIO_SET_FLOW_CTRL_REQUEST,
+                        FTDI_SIO_SET_FLOW_CTRL_REQUEST_TYPE,
+                        value, index, NULL, 0, WDR_TIMEOUT);
+        if (ret < 0)
+                dev_err(&port->dev, "failed to set flow control: %d\n", ret);
 }
 
 /*