Re: [PATCH] Broadcast manager documentation

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 10/08/2013 02:56 AM, Brian Thorne wrote:
> Hi all,
> 
> I wanted to use the bcm module and ended up putting together some basic findings
> that might be a useful addition to the can.txt documentation.

YEAY! documentation!

> I haven't tried submitting any patches before so please point out any mistakes.

From the howto submit patches point of view, it's preferred to send
matches inline, "git send-email" is your friend.

I cannot say anything to the contents, as I've never used the bcm so
far. However a nitpick inline:

> 0001-net-Update-the-CAN-broadcast-manager-documentation.patch
> 
> 
> From 282b4d202b580d57c384dc84aeb7bbb08dff556f Mon Sep 17 00:00:00 2001
> From: Brian Thorne <hardbyte@gmail.com>
> Date: Tue, 8 Oct 2013 12:10:43 +1300
> Subject: [PATCH] net: Update the CAN broadcast manager documentation
> 
> Add content to empty section in controller area network
> documentation.
> 
> Signed-off-by: Brian Thorne <hardbyte@gmail.com>
> ---
>  Documentation/networking/can.txt | 132 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 132 insertions(+)
> 
> diff --git a/Documentation/networking/can.txt b/Documentation/networking/can.txt
> index 820f553..38b1d7e 100644
> --- a/Documentation/networking/can.txt
> +++ b/Documentation/networking/can.txt
> @@ -593,6 +593,138 @@ solution for a couple of reasons:
>        In order to receive such messages, CAN_RAW_RECV_OWN_MSGS must be set.
>  
>    4.2 Broadcast Manager protocol sockets (SOCK_DGRAM)
> +
> +  The Broadcast Manager protocol provides an interface to filter and send
> +  cyclic CAN packets in kernel space.
> +
> +  Periodic transmissions can be modified at runtime; both the message content
> +  and the interval can be altered. Periodic transmissions can use multiple
> +  intervals, sending N messages at a interval, then continuing to send at
> +  another given interval.
> +
> +  Receive filters can be used to down sample frequent messages; detect events
> +  such as message contents changes, packet length changes, and do time-out
> +  monitoring of received messages.
> +
> +  A BCM socket is not used for sending individual can frames, instead a new
> +  special message is defined. The basic BCM frame structure used to
> +  communicate with the broadcast manager and the available operations are
> +  defined in include/linux/can/bcm.h. The basic BCM frame consists of a

It's "include/uapi/linux/can/bcm.h" in recent kernel trees.

> +  message header with an opcode command followed by zero or more can frames.
> +  The broadcast manager sends responses to user space in the same form:
> +
> +    struct bcm_msg_head {
> +            __u32 opcode;                   /* command */
> +            __u32 flags;                    /* special flags */
> +            __u32 count;                    /* run 'count' times with ival1 */
> +            struct timeval ival1, ival2;    /* count and subsequent interval */
> +            canid_t can_id;                 /* unique can_id for task */
> +            __u32 nframes;                  /* number of can_frames following */
> +            struct can_frame frames[0];
> +    };

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
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