A query or an event traveling a pad link. More...

#include <mpipe_dispatch.h>

Data Fields
uint8_t	type
	Dispatch type from mpipe_dispatch_type.
struct mpipe_structure *	caps
	The capability carried, or NULL when the dispatch carries none.
struct mpipe_buffer_pool *	pool
	Buffer pool its proposer makes available (not owned).
struct mpipe_buffer_pool_config	pool_cfg
	A pool config proposed without a pool, negotiated by value.

Detailed Description

A query or an event traveling a pad link.

A dispatch travels a synchronous walk, so it references storage that outlives the walk instead of embedding a copy of everything it carries. It is declared with a designated initializer and has no init function - zero is the neutral value of every field:

struct mpipe_dispatch query = {
        .type = MPIPE_DISPATCH_CAPS,
        .caps = &caps_storage,
};

Field Documentation

◆ caps

struct mpipe_structure* mpipe_dispatch::caps

The capability carried, or NULL when the dispatch carries none.

The creator points this at storage it owns for the whole walk; every other element reads through it and answers by copying INTO it. Repointing it at storage of your own dangles the moment your frame returns.

Value	On a query (in/out storage)	On an event (an announcement)
a capability	the filter to answer within	the format decided on
ANY	no constraint: answer with all you support	never send one
NULL	caller error: nowhere to answer	nothing to announce

A query function may dereference this without checking: a caps query carrying no storage is refused by mpipe_pad_query() with -EINVAL before any of them is called. An event handler must check, since NULL is a valid thing for an event to carry.

A caps event carrying none is a trigger rather than an announcement: a source that knows no format (a file source) still sends one, and the first element that does know one puts it in and announces it downstream.

◆ pool

struct mpipe_buffer_pool* mpipe_dispatch::pool

Buffer pool its proposer makes available (not owned).

◆ pool_cfg

struct mpipe_buffer_pool_config mpipe_dispatch::pool_cfg

A pool config proposed without a pool, negotiated by value.

◆ type

uint8_t mpipe_dispatch::type

Dispatch type from mpipe_dispatch_type.

The documentation for this struct was generated from the following file:

include/zephyr/mpipe/mpipe_dispatch.h