/*
* Media entity
*
* Copyright (C) 2010 Nokia Corporation
*
* Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
* Sakari Ailus <sakari.ailus@iki.fi>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <linux/module.h>
#include <linux/slab.h>
#include <media/media-entity.h>
/**
* media_entity_init - Initialize a media entity
*
* @num_pads: Total number of sink and source pads.
* @extra_links: Initial estimate of the number of extra links.
* @pads: Array of 'num_pads' pads.
*
* The total number of pads is an intrinsic property of entities known by the
* entity driver, while the total number of links depends on hardware design
* and is an extrinsic property unknown to the entity driver. However, in most
* use cases the entity driver can guess the number of links which can safely
* be assumed to be equal to or larger than the number of pads.
*
* For those reasons the links array can be preallocated based on the entity
* driver guess and will be reallocated later if extra links need to be
* created.
*
* This function allocates a links array with enough space to hold at least
* 'num_pads' + 'extra_links' elements. The media_entity::max_links field will
* be set to the number of allocated elements.
*
* The pads array is managed by the entity driver and passed to
* media_entity_init() where its pointer will be stored in the entity structure.
*/
int
media_entity_init(struct media_entity *entity, u16 num_pads,
struct media_pad *pads, u16 extra_links)
{
struct media_link *links;
unsigned int max_links = num_pads + extra_links;
unsigned int i;
links = kzalloc(max_links * sizeof(links[0]), GFP_KERNEL);
if (links == NULL)
return -ENOMEM;
entity->group_id = 0;
entity->max_links = max_links;
entity->num_links = 0;
entity->num_backlinks = 0;
entity->num_pads = num_pads;
entity->pads = pads;
entity->links = links;
for (i = 0; i < num_pads; i++) {
pads[i].entity = entity;
pads[i].index = i;
}
return 0;
}
EXPORT_SYMBOL_GPL(media_entity_init);
void
media_entity_cleanup(struct media_entity *entity)
{
kfree(entity->links);
}
EXPORT_SYMBOL_GPL(media_entity_cleanup);
/* -----------------------------------------------------------------------------
* Graph traversal
*/
static struct media_entity *
media_entity_other(struct media_entity *entity, struct media_link *link)
{
if (link->source->entity == entity)
return link->sink->entity;
else
return link->source->entity;
}
/* push an entity to traversal stack */
static void stack_push(struct media_entity_graph *graph,
struct media_entity *entity)
{
if (graph->top == MEDIA_ENTITY_ENUM_MAX_DEPTH - 1) {
WARN_ON(1);
return;
}
graph->top++;
graph->stack[graph->top].link = 0;
graph->stack[graph->top].entity = entity;
}
static struct media_entity *stack_pop(struct media_entity_graph *graph)
{
struct media_entity *entity;
entity = graph->stack[graph->top].entity;
graph->top--;
return entity;
}
#define stack_peek(en) ((en)->stack[(en)->top - 1].entity)
#define link_top(en) ((en)->stack[(en)->top].link)
#define stack_top(en) ((en)->stack[(en)->top].entity)
/**
* media_entity_graph_walk_start - Start walking the media graph at a given entity
* @graph: Media graph structure that will be used to walk the graph
* @entity: Starting entity
*
* This function initializes the graph traversal structure to walk the entities
* graph starting at the given entity. The traversal structure must not be
* modified by the caller during graph traversal. When done the structure can
* safely be freed.
*/
void media_entity_graph_walk_start(struct media_entity_graph *graph,
struct media_entity *entity)
{
graph->top = 0;
graph->stack[graph->top].entity = NULL;
stack_push(graph, entity);
}
EXPORT_SYMBOL_GPL(media_entity_graph_walk_start);
/**
* media_entity_graph_walk_next - Get the next entity in the graph
* @graph: Media graph structure
*
* Perform a depth-first traversal of the given media entities graph.
*
* The graph structure must have been previously initialized with a call to
* media_entity_graph_walk_start().
*
* Return the next entity in the graph or NULL if the whole graph have been
* traversed.
*/
struct media_entity *
media_entity_graph_walk_next(struct media_entity_graph *graph)
{
if (stack_top(graph) == NULL)
return NULL;
/*
* Depth first search. Push entity to stack and continue from
* top of the stack until no more entities on the level can be
* found.
*/
while (link_top(graph) < stack_top(graph)->num_links) {
struct media_entity *entity = stack_top(graph);
struct media_link *link = &entity->links[link_top(graph)];
struct media_entity *next;
/* The link is not enabled so we do not follow. */
if (!(link->flags & MEDIA_LNK_FL_ENABLED)) {
link_top(graph)++;
continue;
}
/* Get the entity in the other end of the link . */
next = media_entity_other(entity, link);
/* Was it the entity we came here from? */
if (next == stack_peek(graph)) {
link_top(graph)++;
continue;
}
/* Push the new entity to stack and start over. */
link_top(graph)++;
stack_push(graph, next);
}
return stack_pop(graph);
}
EXPORT_SYMBOL_GPL(media_entity_graph_walk_next);
/* -----------------------------------------------------------------------------
* Links management
*/
static struct media_link *media_entity_add_link(struct media_entity *entity)
{
if (entity->num_links >= entity->max_links) {
struct media_link *links = entity->links;
unsigned int max_links = entity->max_links + 2;
unsigned int i;
links = krealloc(links, max_links * sizeof(*links), GFP_KERNEL);
if (links == NULL)
return NULL;
for (i = 0; i < entity->num_links; i++)
links[i].reverse->reverse = &links[i];
entity->max_links = max_links;
entity->links = links;
}
return &entity->links[entity->num_links++];
}
int
media_entity_create_link(struct media_entity *source, u16 source_pad,
struct media_entity *sink, u16 sink_pad, u32 flags)
{
struct media_link *link;
struct media_link *backlink;
BUG_ON(source == NULL || sink == NULL);
BUG_ON(source_pad >= source->num_pads);
BUG_ON(sink_pad >= sink->num_pads);
link = media_entity_add_link(source);
if (link == NULL)
return -ENOMEM;
link->source = &source->pads[source_pad];
link->sink = &sink->pads[sink_pad];
link->flags = flags;
/* Create the backlink. Backlinks are used to help graph traversal and
* are not reported to userspace.
*/
backlink = media_entity_add_link(sink);
if (backlink == NULL) {
source->num_links--;
return -ENOMEM;
}
backlink->source = &source->pads[source_pad];
backlink->sink = &sink->pads[sink_pad];
backlink->flags = flags;
link->reverse = backlink;
backlink->reverse = link;
sink->num_backlinks++;
return 0;
}
EXPORT_SYMBOL_GPL(media_entity_create_link);
