Date:	Thu, 14 Jan 2016 16:30:47 +0000
From:	Martyn Welch <martyn.welch@...labora.co.uk>
To:	Konstantin Shkolnyy <konstantin.shkolnyy@...il.com>,
	johan@...nel.org
CC:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3 RESEND] USB: serial: cp210x: New 16-bit register
 access functions.

On 23/12/15 02:14, Konstantin Shkolnyy wrote:
> cp210x_get_config and cp210x_set_config are cumbersome to use. This change
> introduces new register access functions for 16-bit values, instead of
> the above functions.
>
> Signed-off-by: Konstantin Shkolnyy <konstantin.shkolnyy@...il.com>
> ---
>   drivers/usb/serial/cp210x.c | 155 +++++++++++++++++++++++++++++++-------------
>   1 file changed, 111 insertions(+), 44 deletions(-)
>
> diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
> index fd67958..fd7c4f4 100644
> --- a/drivers/usb/serial/cp210x.c
> +++ b/drivers/usb/serial/cp210x.c
> @@ -422,14 +422,88 @@ static int cp210x_set_config(struct usb_serial_port *port, u8 request,
>   }
>
>   /*
> - * cp210x_set_config_single
> - * Convenience function for calling cp210x_set_config on single data values
> - * without requiring an integer pointer
> + * Reads a variable-sized block of CP210X_ registers, identified by req.
> + * Returns data into buf in native USB byte order.
>    */
> -static inline int cp210x_set_config_single(struct usb_serial_port *port,
> -		u8 request, unsigned int data)
> +static int cp210x_read_reg_block(struct usb_serial_port *port, u8 req,
> +		void *buf, int bufsize)
>   {
> -	return cp210x_set_config(port, request, &data, 2);
> +	struct usb_serial *serial = port->serial;
> +	struct cp210x_port_private *port_priv = usb_get_serial_port_data(port);
> +	void *dmabuf;
> +	int result;
> +
> +	dmabuf = kmalloc(bufsize, GFP_KERNEL);
> +	if (!dmabuf) {
> +		/*
> +		 * FIXME Some callers don't bother to check for error,
> +		 * at least give them consistent junk until they are fixed
> +		 */
> +		memset(buf, 0, bufsize);
> +		return -ENOMEM;
> +	}
> +
> +	result = usb_control_msg(serial->dev, usb_rcvctrlpipe(serial->dev, 0),
> +			req, REQTYPE_INTERFACE_TO_HOST, 0,
> +			port_priv->bInterfaceNumber, dmabuf, bufsize,
> +			USB_CTRL_SET_TIMEOUT);
> +	if (result == bufsize) {
> +		memcpy(buf, dmabuf, bufsize);
> +		result = 0;

I could be wrong, but isn't dmabuf a little-endian stream (hence the 
byte order swapping in the existing set and get functions). Won't this 
break on big endian systems due to the lack of byte swapping?

Martyn

> +	} else {
> +		dev_err(&port->dev, "failed get req 0x%x size %d status: %d\n",
> +				req, bufsize, result);
> +		if (result >= 0)
> +			result = -EPROTO;
> +
> +		/*
> +		 * FIXME Some callers don't bother to check for error,
> +		 * at least give them consistent junk until they are fixed
> +		 */
> +		memset(buf, 0, bufsize);
> +	}
> +
> +	kfree(dmabuf);
> +
> +	return result;
> +}
> +
> +/*
> + * Reads any 16-bit CP210X_ register identified by req.
> + */
> +static int cp210x_read_u16_reg(struct usb_serial_port *port, u8 req, u16 *val)
> +{
> +	__le16 le16_val;
> +	int err;
> +
> +	err = cp210x_read_reg_block(port, req, &le16_val, sizeof(le16_val));
> +	if (err)
> +		return err;
> +
> +	*val = le16_to_cpu(le16_val);
> +	return 0;
> +}
> +
> +/*
> + * Writes any 16-bit CP210X_ register (req) whose value is passed
> + * entirely in the wValue field of the USB request.
> + */
> +static int cp210x_write_u16_reg(struct usb_serial_port *port, u8 req, u16 val)
> +{
> +	struct usb_serial *serial = port->serial;
> +	struct cp210x_port_private *port_priv = usb_get_serial_port_data(port);
> +	int result;
> +
> +	result = usb_control_msg(serial->dev, usb_sndctrlpipe(serial->dev, 0),
> +			req, REQTYPE_HOST_TO_INTERFACE, val,
> +			port_priv->bInterfaceNumber, NULL, 0,
> +			USB_CTRL_SET_TIMEOUT);
> +	if (result < 0) {
> +		dev_err(&port->dev, "failed set request 0x%x status: %d\n",
> +				req, result);
> +	}
> +
> +	return result;
>   }
>
>   /*
> @@ -441,48 +515,47 @@ static inline int cp210x_set_config_single(struct usb_serial_port *port,
>   static int cp210x_detect_swapped_line_ctl(struct usb_serial_port *port)
>   {
>   	struct cp210x_port_private *port_priv = usb_get_serial_port_data(port);
> -	unsigned int line_ctl_save;
> -	unsigned int line_ctl_test;
> +	u16 line_ctl_save;
> +	u16 line_ctl_test;
>   	int err;
>
> -	err = cp210x_get_config(port, CP210X_GET_LINE_CTL, &line_ctl_save, 2);
> +	err = cp210x_read_u16_reg(port, CP210X_GET_LINE_CTL, &line_ctl_save);
>   	if (err)
>   		return err;
>
> -	line_ctl_test = 0x800;
> -	err = cp210x_set_config(port, CP210X_SET_LINE_CTL, &line_ctl_test, 2);
> +	err = cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, 0x800);
>   	if (err)
>   		return err;
>
> -	err = cp210x_get_config(port, CP210X_GET_LINE_CTL, &line_ctl_test, 2);
> +	err = cp210x_read_u16_reg(port, CP210X_GET_LINE_CTL, &line_ctl_test);
>   	if (err)
>   		return err;
>
>   	/* has_swapped_line_ctl is 0 here because port_priv was kzalloced */
>   	if (line_ctl_test == 8) {
>   		port_priv->has_swapped_line_ctl = true;
> -		line_ctl_save = swab16((u16)line_ctl_save);
> +		line_ctl_save = swab16(line_ctl_save);
>   	}
>
> -	return cp210x_set_config(port, CP210X_SET_LINE_CTL, &line_ctl_save, 2);
> +	return cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, line_ctl_save);
>   }
>
>   /*
> - * Must always be called instead of cp210x_get_config(CP210X_GET_LINE_CTL)
> + * Must always be called instead of cp210x_read_u16_reg(CP210X_GET_LINE_CTL)
>    * to workaround cp2108 bug and get correct value.
>    */
> -static int cp210x_get_line_ctl(struct usb_serial_port *port, unsigned int *ctl)
> +static int cp210x_get_line_ctl(struct usb_serial_port *port, u16 *ctl)
>   {
>   	struct cp210x_port_private *port_priv = usb_get_serial_port_data(port);
>   	int err;
>
> -	err = cp210x_get_config(port, CP210X_GET_LINE_CTL, ctl, 2);
> +	err = cp210x_read_u16_reg(port, CP210X_GET_LINE_CTL, ctl);
>   	if (err)
>   		return err;
>
>   	/* Workaround swapped bytes in 16-bit value from CP210X_GET_LINE_CTL */
>   	if (port_priv->has_swapped_line_ctl)
> -		*ctl = swab16((u16)(*ctl));
> +		*ctl = swab16(*ctl);
>
>   	return 0;
>   }
> @@ -531,14 +604,11 @@ static unsigned int cp210x_quantise_baudrate(unsigned int baud)
>
>   static int cp210x_open(struct tty_struct *tty, struct usb_serial_port *port)
>   {
> -	int result;
> +	int err;
>
> -	result = cp210x_set_config_single(port, CP210X_IFC_ENABLE,
> -								UART_ENABLE);
> -	if (result) {
> -		dev_err(&port->dev, "%s - Unable to enable UART\n", __func__);
> -		return result;
> -	}
> +	err = cp210x_write_u16_reg(port, CP210X_IFC_ENABLE, UART_ENABLE);
> +	if (err)
> +		return err;
>
>   	/* Configure the termios structure */
>   	cp210x_get_termios(tty, port);
> @@ -552,15 +622,12 @@ static int cp210x_open(struct tty_struct *tty, struct usb_serial_port *port)
>
>   static void cp210x_close(struct usb_serial_port *port)
>   {
> -	unsigned int purge_ctl;
> -
>   	usb_serial_generic_close(port);
>
>   	/* Clear both queues; cp2108 needs this to avoid an occasional hang */
> -	purge_ctl = PURGE_ALL;
> -	cp210x_set_config(port, CP210X_PURGE, &purge_ctl, 2);
> +	cp210x_write_u16_reg(port, CP210X_PURGE, PURGE_ALL);
>
> -	cp210x_set_config_single(port, CP210X_IFC_ENABLE, UART_DISABLE);
> +	cp210x_write_u16_reg(port, CP210X_IFC_ENABLE, UART_DISABLE);
>   }
>
>   /*
> @@ -640,7 +707,7 @@ static void cp210x_get_termios_port(struct usb_serial_port *port,
>   	struct device *dev = &port->dev;
>   	unsigned int cflag, modem_ctl[4];
>   	unsigned int baud;
> -	unsigned int bits;
> +	u16 bits;
>
>   	cp210x_get_config(port, CP210X_GET_BAUDRATE, &baud, 4);
>
> @@ -673,14 +740,14 @@ static void cp210x_get_termios_port(struct usb_serial_port *port,
>   		cflag |= CS8;
>   		bits &= ~BITS_DATA_MASK;
>   		bits |= BITS_DATA_8;
> -		cp210x_set_config(port, CP210X_SET_LINE_CTL, &bits, 2);
> +		cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits);
>   		break;
>   	default:
>   		dev_dbg(dev, "%s - Unknown number of data bits, using 8\n", __func__);
>   		cflag |= CS8;
>   		bits &= ~BITS_DATA_MASK;
>   		bits |= BITS_DATA_8;
> -		cp210x_set_config(port, CP210X_SET_LINE_CTL, &bits, 2);
> +		cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits);
>   		break;
>   	}
>
> @@ -711,7 +778,7 @@ static void cp210x_get_termios_port(struct usb_serial_port *port,
>   		dev_dbg(dev, "%s - Unknown parity mode, disabling parity\n", __func__);
>   		cflag &= ~PARENB;
>   		bits &= ~BITS_PARITY_MASK;
> -		cp210x_set_config(port, CP210X_SET_LINE_CTL, &bits, 2);
> +		cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits);
>   		break;
>   	}
>
> @@ -723,7 +790,7 @@ static void cp210x_get_termios_port(struct usb_serial_port *port,
>   	case BITS_STOP_1_5:
>   		dev_dbg(dev, "%s - stop bits = 1.5 (not supported, using 1 stop bit)\n", __func__);
>   		bits &= ~BITS_STOP_MASK;
> -		cp210x_set_config(port, CP210X_SET_LINE_CTL, &bits, 2);
> +		cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits);
>   		break;
>   	case BITS_STOP_2:
>   		dev_dbg(dev, "%s - stop bits = 2\n", __func__);
> @@ -732,7 +799,7 @@ static void cp210x_get_termios_port(struct usb_serial_port *port,
>   	default:
>   		dev_dbg(dev, "%s - Unknown number of stop bits, using 1 stop bit\n", __func__);
>   		bits &= ~BITS_STOP_MASK;
> -		cp210x_set_config(port, CP210X_SET_LINE_CTL, &bits, 2);
> +		cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits);
>   		break;
>   	}
>
> @@ -806,7 +873,7 @@ static void cp210x_set_termios(struct tty_struct *tty,
>   {
>   	struct device *dev = &port->dev;
>   	unsigned int cflag, old_cflag;
> -	unsigned int bits;
> +	u16 bits;
>   	unsigned int modem_ctl[4];
>
>   	cflag = tty->termios.c_cflag;
> @@ -845,7 +912,7 @@ static void cp210x_set_termios(struct tty_struct *tty,
>   			bits |= BITS_DATA_8;
>   			break;
>   		}
> -		if (cp210x_set_config(port, CP210X_SET_LINE_CTL, &bits, 2))
> +		if (cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits))
>   			dev_dbg(dev, "Number of data bits requested not supported by device\n");
>   	}
>
> @@ -872,7 +939,7 @@ static void cp210x_set_termios(struct tty_struct *tty,
>   				}
>   			}
>   		}
> -		if (cp210x_set_config(port, CP210X_SET_LINE_CTL, &bits, 2))
> +		if (cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits))
>   			dev_dbg(dev, "Parity mode not supported by device\n");
>   	}
>
> @@ -886,7 +953,7 @@ static void cp210x_set_termios(struct tty_struct *tty,
>   			bits |= BITS_STOP_1;
>   			dev_dbg(dev, "%s - stop bits = 1\n", __func__);
>   		}
> -		if (cp210x_set_config(port, CP210X_SET_LINE_CTL, &bits, 2))
> +		if (cp210x_write_u16_reg(port, CP210X_SET_LINE_CTL, bits))
>   			dev_dbg(dev, "Number of stop bits requested not supported by device\n");
>   	}
>
> @@ -926,7 +993,7 @@ static int cp210x_tiocmset(struct tty_struct *tty,
>   static int cp210x_tiocmset_port(struct usb_serial_port *port,
>   		unsigned int set, unsigned int clear)
>   {
> -	unsigned int control = 0;
> +	u16 control = 0;
>
>   	if (set & TIOCM_RTS) {
>   		control |= CONTROL_RTS;
> @@ -947,7 +1014,7 @@ static int cp210x_tiocmset_port(struct usb_serial_port *port,
>
>   	dev_dbg(&port->dev, "%s - control = 0x%.4x\n", __func__, control);
>
> -	return cp210x_set_config(port, CP210X_SET_MHS, &control, 2);
> +	return cp210x_write_u16_reg(port, CP210X_SET_MHS, control);
>   }
>
>   static void cp210x_dtr_rts(struct usb_serial_port *p, int on)
> @@ -981,7 +1048,7 @@ static int cp210x_tiocmget(struct tty_struct *tty)
>   static void cp210x_break_ctl(struct tty_struct *tty, int break_state)
>   {
>   	struct usb_serial_port *port = tty->driver_data;
> -	unsigned int state;
> +	u16 state;
>
>   	if (break_state == 0)
>   		state = BREAK_OFF;
> @@ -989,7 +1056,7 @@ static void cp210x_break_ctl(struct tty_struct *tty, int break_state)
>   		state = BREAK_ON;
>   	dev_dbg(&port->dev, "%s - turning break %s\n", __func__,
>   		state == BREAK_OFF ? "off" : "on");
> -	cp210x_set_config(port, CP210X_SET_BREAK, &state, 2);
> +	cp210x_write_u16_reg(port, CP210X_SET_BREAK, state);
>   }
>
>   static int cp210x_port_probe(struct usb_serial_port *port)
>

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