Date:	Tue, 26 Jan 2010 09:50:54 -0800
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	sjur.brandeland@...ricsson.com
Cc:	netdev@...r.kernel.org, davem@...emloft.net, marcel@...tmann.org,
	stefano.babic@...ic.homelinux.org
Subject: Re: [PATCH net-next-2.6 10/13] net-caif: add kernel-client API for
 CAIF

On Wed, 20 Jan 2010 23:55:27 +0100 sjur.brandeland@...ricsson.com wrote:

> From: Sjur Braendeland <sjur.brandeland@...ricsson.com>
> 
> This patch provides a CAIF API for managing CAIF devices from
> kernel modules.
> 
> Signed-off-by: Sjur Braendeland <sjur.brandeland@...ricsson.com>
> ---
>  include/net/caif/caif_kernel.h |  309 ++++++++++++++++++++++++++++++++++++++++
>  net/caif/caif_chnlif.c         |  177 +++++++++++++++++++++++
>  2 files changed, 486 insertions(+), 0 deletions(-)
> 
> diff --git a/include/net/caif/caif_kernel.h b/include/net/caif/caif_kernel.h
> new file mode 100644
> index 0000000..6617a8f
> --- /dev/null
> +++ b/include/net/caif/caif_kernel.h
> @@ -0,0 +1,309 @@
> +/*
> + * CAIF Kernel Internal interface for configuring and accessing
> + * CAIF Channels.
> + * Copyright (C) ST-Ericsson AB 2010
> + * Author:	Sjur Brendeland/ sjur.brandeland@...ricsson.com
> + * License terms: GNU General Public License (GPL) version 2
> + */
> +
> +#ifndef CAIF_KERNEL_H_
> +#define CAIF_KERNEL_H_
> +#include <linux/caif/caif_config.h>
> +struct sk_buff;
> +

Hi,

I'm probably repeating myself here, but this function documentation
is not formatted in the way which the Linux kernel expects/wants.

Some of the others (after this one) use "/**" to begin the comment block.
In kernel-land, that is used only for kernel-doc formatted notation.


> +/*!\page  caif_kernel.h
> + * This is the specification of the CAIF kernel internal interface to
> + * CAIF Channels.
> + * This interface follows the pattern used in Linux device drivers with a
> + *  struct \ref caif_device
> + * holding control data handling each device instance.
> + *
> + * The functional interface consists of a few basic functions:
> + *  - \ref caif_add_device             Configure and connect the CAIF
> + *               channel to the remote end. Configuration is described in
> + *               \ref caif_channel_config.
> + *  - \ref caif_remove_device          Disconnect and remove the channel.
> + *  - \ref caif_transmit               Sends a CAIF message on the link.
> + *  - \ref caif_device.receive_cb      Receive callback function for
> + *                receiving packets.
> + *  - \ref caif_device.control_cb      Control information from the CAIF stack.
> + *  - \ref caif_flow_control           Send flow control message to remote end.
> + *
> + *
> + * Details:
> + * \see { caif_kernel }
> + *
> + * \code
> + *
> +#include <net/caif/caif_kernel.h>"
> +
> +	static void my_receive(struct caif_device *dev, struct sk_buff *skb)
> +	{
> +	...
> +	}
> +
> +	static void my_control(struct caif_device *dev, enum caif_control ctrl)
> +	{
> +	....
> +	}
> +
> +	int kernel_caif_usage_example()
> +	{
> +		struct sk_buff *skb;
> +		char *message = "hello";
> +
> +		// Connect the channel
> +		struct caif_device caif_dev = {
> +			.caif_config = {
> +				.name = "MYDEV",
> +				.priority = CAIF_PRIO_NORMAL,
> +				.type = CAIF_CHTY_UTILITY,
> +				.phy_pref = CAIF_PHYPREF_LOW_LAT,
> +				.u.utility.name = "CAIF_PSOCK_TEST",
> +				.u.utility.params = {0x01},
> +				.u.utility.paramlen = 1,
> +		},
> +
> +		.receive_cb = my_receive,
> +		.control_cb = my_control,
> +
> +		};
> +	ret = caif_add_device(&caif_dev);
> +	if (ret)
> +	goto error;
> +
> +	// Send a packet
> +	skb = caif_create_skb(message, strlen(message));
> +	ret = caif_transmit(&caif_dev, skb);
> +	if (ret)
> +		goto error;
> +
> +	// Remove device
> +	ret = caif_remove_device(&caif_dev);
> +	if (ret)
> +		goto error;
> +
> +}
> +
> +* \endcode
> +*
> +* \section Linux Socket Buffer (SKB)
> +    *          When sending out packets on a connection (\ref caif_transmit)
> +    *          the CAIF stack will add CAIF protocol headers.
> +    *          This requires space in the SKB.
> +    *          CAIF has defined \ref CAIF_SKB_HEAD_RESERVE for minimum
> +    *          required reserved head-space in the packet and
> +    *          \ref CAIF_SKB_TAIL_RESERVE for minimum reserved tail-space.
> +    *
> +    *          \b NOTE The Linux kernel SKB operations panic if not
> +    *                  enough space is available!
> +    *
> +    */
> +
> +    /*! \addtogroup caif_kernel
> +     *  @{
> +     */
> +
> +struct caif_device;
> +
> +	/** Minimum required CAIF socket buffer head-space */
> +#define CAIF_SKB_HEAD_RESERVE 32
> +
> +	/** Minimum required CAIF socket buffer tail-space */
> +#define CAIF_SKB_TAIL_RESERVE 32
> +
> +	/** CAIF control information (used in \ref caif_device.control_cb)
> +	 *   used for receiving control information from the modem.
> +	 */
> +enum caif_control {
> +	/** Modem has sent Flow-ON, Clients can start transmitting
> +	 *  data using \ref caif_transmit.
> +	 */
> +	CAIF_CONTROL_FLOW_ON = 0,
> +	/** Modem has sent Flow-OFF, Clients must stop transmitting
> +	 * data using \ref caif_transmit.
> +	 */
> +	CAIF_CONTROL_FLOW_OFF = 1,
> +
> +	/** Channel creation is complete. This is an acknowledgement to
> +	 *  \ref caif_add_device from the modem.
> +	 *  The channel is ready for transmit (Flow-state is ON).
> +	 */
> +	CAIF_CONTROL_DEV_INIT = 3,
> +
> +	/** Spontaneous close request from the modem, only applicable
> +	 *   for utility link. The client should respond by calling
> +	 *   \ref caif_remove_device.
> +	 */
> +	CAIF_CONTROL_REMOTE_SHUTDOWN = 4,
> +
> +	/** Channel disconnect is complete. This is an acknowledgement to
> +	 *  \ref caif_remove_device from the modem.
> +	 *  \ref caif_transmit or \ref caif_flow_control must not be
> +	 *  called after this.
> +	 */
> +	CAIF_CONTROL_DEV_DEINIT = 5,
> +
> +	/** Channel creation has failed. This is a negative acknowledgement
> +	 *  to \ref caif_add_device from the modem.
> +	 */
> +	CAIF_CONTROL_DEV_INIT_FAILED = 6
> +};
> +
> +/** Flow control information (used in \ref caif_device.control_cb) used
> + *  for controlling outgoing flow.
> + */
> +enum caif_flowctrl {
> +	/** Flow Control is ON, transmit function can start sending data */
> +	CAIF_FLOWCTRL_ON = 0,
> +	/** Flow Control is OFF, transmit function should stop sending data */
> +	CAIF_FLOWCTRL_OFF = 1,
> +};
> +
> +/** Transmits CAIF packets on channel.
> + * This function is non-blocking and safe to use in tasklet context.
> + * The CAIF stack takes ownership of the socket buffer (SKB) after calling
> + * \ref caif_transmit.
> + * This means that the user cannot access the SKB afterwards; this applies
> + * even in error situations.
> + *
> + * @return 0 on success, < 0 upon error.
> + *
> + * @param[in] skb         Socket buffer holding data to be written.
> + * @param[in] dev         Structure used when creating the channel
> + *
> + *
> + * Error codes:
> + *  - \b ENOTCONN,   The channel is not connected.
> + *  - \b EPROTO,     Protocol error (or SKB is faulty)
> + *  - \b EIO         IO error (unspecified error)
> + */
> +int caif_transmit(struct caif_device *dev, struct sk_buff *skb);
> +
> +/** Function for sending flow ON / OFF to remote end.
> + * This function is non-blocking and safe to use in tasklet context.
> + *
> + * @param[in] dev        Reference to device data.
> + * @param[in] flow       Flow control information.
> +
> + * @return 0 on success, < 0 upon error.
> + * Error codes:
> + *  - \b ENOTCONN,   The channel is not connected.
> + *  - \b EPROTO,     Protocol error.
> + *  - \b EIO         IO error (unspecified error).
> + */
> +int caif_flow_control(struct caif_device *dev, enum caif_flowctrl flow);
> +
> +/** Handle for kernel internal CAIF channels.
> + * All fields in this structure must be filled in by client before calling
> + * \ref caif_add_device (except _caif_handle).
> + */
> +struct caif_device {
> +
> +    /** Channel configuration parameter. Contains information about type
> +     *	and configuration of the channel.
> +     *  This must be set before calling \ref caif_add_device.
> +     */
> +	struct caif_channel_config caif_config;
> +
> +
> +    /** Callback function for receiving CAIF Packets from channel.
> +     * This callback is called from softirq context (tasklet).
> +     * The receiver <b> must </b> free the SKB.
> +     * <b> DO NOT BLOCK IN THIS FUNCTION! </b>
> +     *
> +     * If the client has to do blocking operations then
> +     * it must start its own work queue (or kernel thread).
> +     *
> +     * @param[in] dev       Reference to device data.
> +     * @param[in] skb       Socket buffer with received data.
> +     */
> +	void (*receive_cb) (struct caif_device *dev, struct sk_buff *skb);
> +
> +
> +    /** Callback function for notifying flow control from remote end - see
> +     *  \ref caif_control.
> +     * This callback is called from from softirq context (tasklet).
> +     *
> +     * <b> DO NOT BLOCK IN THIS FUNCTION! </b>
> +     *
> +     * Client must not call \ref caif_transmit from this function.
> +     *
> +     * If the client has queued packets to send then
> +     * it must start its own thread to do \ref caif_transmit.
> +     *
> +     * @param[in] dev        Reference to device data.
> +     * @param[in] ctrl       CAIF control info \ref caif_control.
> +     *                       e.g. Flow control
> +     *                       \ref CAIF_CONTROL_FLOW_ON or
> +     *                       \ref CAIF_CONTROL_FLOW_OFF
> +     */
> +	void (*control_cb) (struct caif_device *dev, enum caif_control ctrl);
> +
> +    /** This is a CAIF private attribute, holding CAIF internal reference
> +     * to the CAIF stack. Do not update this field.
> +     */
> +	void *_caif_handle;
> +
> +    /** This field may be filled in by client for their own usage. */
> +	void *user_data;
> +};
> +
> +/** Add (connect) a CAIF Channel.
> + * This function is non-blocking. The channel connect is reported in
> + * \ref caif_device.control_cb.
> + * The channel is not open until \ref caif_device.control_cb is called with
> + * \ref CAIF_CONTROL_DEV_INIT.
> + * If setting up the channel fails then \ref caif_device.control_cb is called
> + * with \ref CAIF_CONTROL_DEV_INIT_FAILED.
> + *
> + * \ref caif_transmit, \ref caif_flow_control or \ref caif_remove_device must
> + * not be called before receiveing CAIF_CONTROL_DEV_INIT.
> + * @return 0 on success, < 0 on failure.
> + *
> + * Error codes:
> + * - \b -EINVAL    Invalid arguments
> + * - \b -ENODEV    No PHY device exists.
> + * - \b -EIO       IO error (unspecified error)
> + */
> +int caif_add_device(struct caif_device *dev);
> +
> +/** Disconnect a CAIF Channel
> + * This function is non-blocking.
> + * The channel has not been disconnected until \ref caif_device : control_cb is
> + * called with \ref CAIF_CONTROL_DEV_DEINIT.
> + * \ref caif_transmit or \ref caif_flow_control \b must not be called after
> + * receiving \ref CAIF_CONTROL_DEV_DEINIT.
> + * The client is responsible for freeing the \ref caif_device structure after
> + * receiving  \ref CAIF_CONTROL_DEV_DEINIT (if applicable).
> + * @return 0 on success.
> + *
> + * - \b EIO       IO error (unspecified error)
> + */
> +int caif_remove_device(struct caif_device *caif_dev);
> +
> +/** Convenience function for allocating a socket buffer for usage with CAIF
> + * and copy user data into the socket buffer.
> + * @param[in] data 		User data to send with CAIF.
> + * @param[in] data_length 	Length of data to send.
> + * @return 	New socket buffer containing user data.
> + */
> +struct sk_buff *caif_create_skb(unsigned char *data, unsigned int data_length);
> +
> +/** Convenience function for extracting data from a socket buffer (SKB) and
> + *  then destroying the SKB.
> + *  Copies data from the SKB and then frees the SKB.
> + * @param[in] skb	SKB to extract data from. SKB will be freed after
> + *			extracting data.
> + *
> + * @param[in] data	User data buffer to extract packet data into.
> + * @param[in] max_length User data buffer length,
> + * @return number of bytes extracted; < 0 upon error.
> + *
> + */
> +int caif_extract_and_destroy_skb(struct sk_buff *skb, unsigned char *data,
> +				 unsigned int max_length);
> +
> +/*! @} */
> +
> +#endif				/* CAIF_KERNEL_H_ */


---
~Randy
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