[4/4] USB: serial: ftdi_sio: clean up flow control management

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Fri, May 18, 2018 at 03:25:50PM +0200, Johan Hovold wrote:
> Clean up the somewhat convoluted hardware-assisted flow control
> handling.
> 
> Signed-off-by: Johan Hovold <johan@kernel.org>
> ---
>  drivers/usb/serial/ftdi_sio.c | 81 ++++++++++-------------------------
>  1 file 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 @@ static void ftdi_set_termios(struct tty_struct *tty,
>  			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);
>  }
>  
>  /*

Wow, much simpler, nice work.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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