Re: [Xenomai-core] rt_pipe_* usage

[Philippe Gerum <rpm@xenomai.org>]

Ignacio García Pérez wrote:
> Philippe Gerum wrote:
> 
> 
>>Ignacio García Pérez wrote:
>>
>>
>>>>>RT_PIPE_MSG *m = rt_pipe_alloc(sizeof(mystruct_t));
>>>>>mystruct_t *p = (mystruct_t *)P_MSGPTR(m);
>>>>>p->whatever1 = X;
>>>>>p->whatever2 = X;
>>>>>rt_pipe_send(&mypipe, m, sizeof(mystruct_t), P_NORMAL);
>>>>>
>>>>>If this is correct, why do I have to specify the size of mystruct_t
>>>>>*twice*. Can't it be initialized by rt_pipe_alloc ?.
>>>>
>>>>
>>>>It's initialized actually (*).
>>>>
>>>
>>>So, what's the sense of having to specify it again whet calling
>>>rt_pipe_send ?
>>>
>>
>>Because you may (pre-)allocate more than you really need to send
>>afterwards.
>>
> 
> I guess this should be explained in the docs. Please consider the small
> patch I attach.
> 

Ok, applied. Thanks.

> Nacho.
> 
> 
> ------------------------------------------------------------------------
> 
> Index: skins/native/pipe.c
> ===================================================================
> --- skins/native/pipe.c	(revision 143)
> +++ skins/native/pipe.c	(working copy)
> @@ -598,7 +598,11 @@
>   *
>   * @param size The size in bytes of the message (payload data
>   * only). Zero is a valid value, in which case the service returns
> - * immediately without sending any message.
> + * immediately without sending any message. This parameter allows
> + * you to actually send less data than you reserved using the
> + * rt_pipe_alloc() service, which may be the case if you did not
> + * know how much space you needed at the time of allocation. In all
> + * other cases it may be more convenient to just pass P_MSGSIZE(msg).
>   *
>   * Additionally, rt_pipe_send() causes any data buffered by
>   * rt_pipe_stream() to be flushed prior to sending the message. For


-- 

Philippe.