Re: [PATCH v3 1/4] USB: serial: cp210x: New register access functions.

[Martyn Welch <martyn.welch@collabora.co.uk>]

On 02/01/16 03:11, Konstantin Shkolnyy wrote:
> cp210x_get_config and cp210x_set_config are cumbersome to use. This change
> introduces new register access functions to replace them. New functions
> are not yet called - the switch is done gradually in following changes.
>
> Signed-off-by: Konstantin Shkolnyy <konstantin.shkolnyy-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> ---
> change in v3: Presented new function addition as a separate patch #1,
> to simplify code review.
>
>   drivers/usb/serial/cp210x.c | 166 ++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 166 insertions(+)
>
> diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
> index fd67958..324eb7e 100644
> --- a/drivers/usb/serial/cp210x.c
> +++ b/drivers/usb/serial/cp210x.c
> @@ -323,6 +323,172 @@ struct cp210x_comm_status {
>   #define PURGE_ALL		0x000f
>
>   /*
> + * Reads a variable-sized block of CP210X_ registers, identified by req.
> + * Returns data into buf in native USB byte order.
> + */
> +static int cp210x_read_reg_block(struct usb_serial_port *port, u8 req,
> +		void *buf, int bufsize)
> +{
> +	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;
> +	} 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 32-bit CP210X_ register identified by req.
> + */
> +static int cp210x_read_u32_reg(struct usb_serial_port *port, u8 req, u32 *val)
> +{
> +	__le32 le32_val;
> +	int err;
> +
> +	err = cp210x_read_reg_block(port, req, &le32_val, sizeof(le32_val));
> +	if (err) {
> +		/*
> +		 * FIXME Some callers don't bother to check for error,
> +		 * at least give them consistent junk until they are fixed
> +		 */
> +		*val = 0;
> +		return err;
> +	}
> +
> +	*val = le32_to_cpu(le32_val);
> +
> +	return 0;
> +}
> +
> +/*
> + * 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;
> +}
> +
> +/*
> + * Reads any 8-bit CP210X_ register identified by req.
> + */
> +static int cp210x_read_u8_reg(struct usb_serial_port *port, u8 req, u8 *val)
> +{
> +	return cp210x_read_reg_block(port, req, val, sizeof(*val));
> +}
> +
> +/*
> + * 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)

Think this needs a different name to draw more attention to the fact 
that it writes in a different way from cp210x_write_u32_reg and how the 
cp210x_read_uXX_reg read.

Martyn

> +{
> +	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;
> +}
> +
> +/*
> + * Writes a variable-sized block of CP210X_ registers, identified by req.
> + * Data in buf must be in native USB byte order.
> + */
> +static int cp210x_write_reg_block(struct usb_serial_port *port, u8 req,
> +		void *buf, int bufsize)
> +{
> +	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)
> +		return -ENOMEM;
> +
> +	memcpy(dmabuf, buf, bufsize);
> +
> +	result = usb_control_msg(serial->dev, usb_sndctrlpipe(serial->dev, 0),
> +			req, REQTYPE_HOST_TO_INTERFACE, 0,
> +			port_priv->bInterfaceNumber, dmabuf, bufsize,
> +			USB_CTRL_SET_TIMEOUT);
> +
> +	kfree(dmabuf);
> +
> +	if (result == bufsize) {
> +		result = 0;
> +	} else {
> +		dev_err(&port->dev, "failed set req 0x%x size %d status: %d\n",
> +				req, bufsize, result);
> +		if (result >= 0)
> +			result = -EPROTO;
> +	}
> +
> +	return result;
> +}
> +
> +/*
> + * Writes any 32-bit CP210X_ register identified by req.
> + */
> +static int cp210x_write_u32_reg(struct usb_serial_port *port, u8 req, u32 val)
> +{
> +	__le32 le32_val;
> +
> +	le32_val = cpu_to_le32(val);
> +
> +	return cp210x_write_reg_block(port, req, &le32_val, sizeof(le32_val));
> +}
> +
> +/*
>    * cp210x_get_config
>    * Reads from the CP210x configuration registers
>    * 'size' is specified in bytes.
>