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![Sakari Ailus](/assets/img/avatar_default.png)
Add media entity graph traversal. The traversal follows enabled links by depth first. Traversing graph backwards is prevented by comparing the next possible entity in the graph with the previous one. Multiply connected graphs are thus not supported. Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Vimarsh Zutshi <vimarsh.zutshi@gmail.com> Acked-by: Hans Verkuil <hverkuil@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
262 lines
7.3 KiB
C
262 lines
7.3 KiB
C
/*
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* Media entity
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*
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* Copyright (C) 2010 Nokia Corporation
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*
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* Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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* Sakari Ailus <sakari.ailus@iki.fi>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <media/media-entity.h>
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/**
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* media_entity_init - Initialize a media entity
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*
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* @num_pads: Total number of sink and source pads.
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* @extra_links: Initial estimate of the number of extra links.
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* @pads: Array of 'num_pads' pads.
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*
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* The total number of pads is an intrinsic property of entities known by the
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* entity driver, while the total number of links depends on hardware design
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* and is an extrinsic property unknown to the entity driver. However, in most
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* use cases the entity driver can guess the number of links which can safely
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* be assumed to be equal to or larger than the number of pads.
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*
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* For those reasons the links array can be preallocated based on the entity
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* driver guess and will be reallocated later if extra links need to be
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* created.
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*
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* This function allocates a links array with enough space to hold at least
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* 'num_pads' + 'extra_links' elements. The media_entity::max_links field will
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* be set to the number of allocated elements.
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*
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* The pads array is managed by the entity driver and passed to
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* media_entity_init() where its pointer will be stored in the entity structure.
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*/
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int
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media_entity_init(struct media_entity *entity, u16 num_pads,
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struct media_pad *pads, u16 extra_links)
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{
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struct media_link *links;
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unsigned int max_links = num_pads + extra_links;
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unsigned int i;
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links = kzalloc(max_links * sizeof(links[0]), GFP_KERNEL);
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if (links == NULL)
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return -ENOMEM;
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entity->group_id = 0;
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entity->max_links = max_links;
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entity->num_links = 0;
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entity->num_backlinks = 0;
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entity->num_pads = num_pads;
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entity->pads = pads;
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entity->links = links;
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for (i = 0; i < num_pads; i++) {
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pads[i].entity = entity;
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pads[i].index = i;
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}
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return 0;
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}
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EXPORT_SYMBOL_GPL(media_entity_init);
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void
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media_entity_cleanup(struct media_entity *entity)
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{
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kfree(entity->links);
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}
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EXPORT_SYMBOL_GPL(media_entity_cleanup);
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/* -----------------------------------------------------------------------------
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* Graph traversal
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*/
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static struct media_entity *
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media_entity_other(struct media_entity *entity, struct media_link *link)
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{
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if (link->source->entity == entity)
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return link->sink->entity;
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else
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return link->source->entity;
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}
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/* push an entity to traversal stack */
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static void stack_push(struct media_entity_graph *graph,
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struct media_entity *entity)
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{
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if (graph->top == MEDIA_ENTITY_ENUM_MAX_DEPTH - 1) {
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WARN_ON(1);
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return;
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}
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graph->top++;
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graph->stack[graph->top].link = 0;
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graph->stack[graph->top].entity = entity;
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}
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static struct media_entity *stack_pop(struct media_entity_graph *graph)
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{
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struct media_entity *entity;
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entity = graph->stack[graph->top].entity;
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graph->top--;
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return entity;
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}
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#define stack_peek(en) ((en)->stack[(en)->top - 1].entity)
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#define link_top(en) ((en)->stack[(en)->top].link)
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#define stack_top(en) ((en)->stack[(en)->top].entity)
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/**
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* media_entity_graph_walk_start - Start walking the media graph at a given entity
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* @graph: Media graph structure that will be used to walk the graph
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* @entity: Starting entity
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*
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* This function initializes the graph traversal structure to walk the entities
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* graph starting at the given entity. The traversal structure must not be
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* modified by the caller during graph traversal. When done the structure can
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* safely be freed.
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*/
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void media_entity_graph_walk_start(struct media_entity_graph *graph,
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struct media_entity *entity)
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{
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graph->top = 0;
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graph->stack[graph->top].entity = NULL;
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stack_push(graph, entity);
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}
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EXPORT_SYMBOL_GPL(media_entity_graph_walk_start);
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/**
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* media_entity_graph_walk_next - Get the next entity in the graph
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* @graph: Media graph structure
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*
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* Perform a depth-first traversal of the given media entities graph.
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*
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* The graph structure must have been previously initialized with a call to
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* media_entity_graph_walk_start().
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*
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* Return the next entity in the graph or NULL if the whole graph have been
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* traversed.
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*/
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struct media_entity *
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media_entity_graph_walk_next(struct media_entity_graph *graph)
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{
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if (stack_top(graph) == NULL)
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return NULL;
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/*
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* Depth first search. Push entity to stack and continue from
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* top of the stack until no more entities on the level can be
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* found.
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*/
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while (link_top(graph) < stack_top(graph)->num_links) {
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struct media_entity *entity = stack_top(graph);
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struct media_link *link = &entity->links[link_top(graph)];
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struct media_entity *next;
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/* The link is not enabled so we do not follow. */
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if (!(link->flags & MEDIA_LNK_FL_ENABLED)) {
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link_top(graph)++;
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continue;
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}
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/* Get the entity in the other end of the link . */
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next = media_entity_other(entity, link);
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/* Was it the entity we came here from? */
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if (next == stack_peek(graph)) {
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link_top(graph)++;
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continue;
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}
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/* Push the new entity to stack and start over. */
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link_top(graph)++;
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stack_push(graph, next);
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}
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return stack_pop(graph);
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}
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EXPORT_SYMBOL_GPL(media_entity_graph_walk_next);
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/* -----------------------------------------------------------------------------
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* Links management
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*/
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static struct media_link *media_entity_add_link(struct media_entity *entity)
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{
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if (entity->num_links >= entity->max_links) {
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struct media_link *links = entity->links;
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unsigned int max_links = entity->max_links + 2;
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unsigned int i;
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links = krealloc(links, max_links * sizeof(*links), GFP_KERNEL);
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if (links == NULL)
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return NULL;
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for (i = 0; i < entity->num_links; i++)
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links[i].reverse->reverse = &links[i];
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entity->max_links = max_links;
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entity->links = links;
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}
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return &entity->links[entity->num_links++];
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}
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int
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media_entity_create_link(struct media_entity *source, u16 source_pad,
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struct media_entity *sink, u16 sink_pad, u32 flags)
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{
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struct media_link *link;
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struct media_link *backlink;
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BUG_ON(source == NULL || sink == NULL);
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BUG_ON(source_pad >= source->num_pads);
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BUG_ON(sink_pad >= sink->num_pads);
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link = media_entity_add_link(source);
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if (link == NULL)
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return -ENOMEM;
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link->source = &source->pads[source_pad];
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link->sink = &sink->pads[sink_pad];
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link->flags = flags;
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/* Create the backlink. Backlinks are used to help graph traversal and
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* are not reported to userspace.
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*/
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backlink = media_entity_add_link(sink);
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if (backlink == NULL) {
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source->num_links--;
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return -ENOMEM;
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}
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backlink->source = &source->pads[source_pad];
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backlink->sink = &sink->pads[sink_pad];
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backlink->flags = flags;
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link->reverse = backlink;
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backlink->reverse = link;
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sink->num_backlinks++;
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return 0;
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}
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EXPORT_SYMBOL_GPL(media_entity_create_link);
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