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[media] media: Add support for circular graph traversal

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The graph traversal API (media_entity_graph_walk_*) doesn't support
cyclic graphs and will fail to correctly walk a graph when circular
links exist. Support circular graph traversal by checking whether an
entity has already been visited before pushing it to the stack.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Sakari Ailus <sakari.ailus@iki.fi>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
This commit is contained in:
Laurent Pinchart 2013-06-07 12:45:11 -03:00 committed by Mauro Carvalho Chehab
parent 3a9677063f
commit 5c7b25b90d
2 changed files with 15 additions and 3 deletions
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14
drivers/media/media-entity.c
View File

@ -20,6 +20,7 @@
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <linux/bitmap.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <media/media-entity.h>
@ -121,7 +122,6 @@ static struct media_entity *stack_pop(struct media_entity_graph *graph)
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)
@ -140,6 +140,12 @@ void media_entity_graph_walk_start(struct media_entity_graph *graph,
{
graph->top = 0;
graph->stack[graph->top].entity = NULL;
bitmap_zero(graph->entities, MEDIA_ENTITY_ENUM_MAX_ID);
if (WARN_ON(entity->id >= MEDIA_ENTITY_ENUM_MAX_ID))
return;
__set_bit(entity->id, graph->entities);
stack_push(graph, entity);
}
EXPORT_SYMBOL_GPL(media_entity_graph_walk_start);
@ -180,9 +186,11 @@ media_entity_graph_walk_next(struct media_entity_graph *graph)
/* Get the entity in the other end of the link . */
next = media_entity_other(entity, link);
if (WARN_ON(next->id >= MEDIA_ENTITY_ENUM_MAX_ID))
return NULL;
/* Was it the entity we came here from? */
if (next == stack_peek(graph)) {
/* Has the entity already been visited? */
if (__test_and_set_bit(next->id, graph->entities)) {
link_top(graph)++;
continue;
}

4
include/media/media-entity.h
View File

@ -23,6 +23,7 @@
#ifndef _MEDIA_ENTITY_H
#define _MEDIA_ENTITY_H
#include <linux/bitops.h>
#include <linux/list.h>
#include <linux/media.h>
@ -113,12 +114,15 @@ static inline u32 media_entity_subtype(struct media_entity *entity)
}
#define MEDIA_ENTITY_ENUM_MAX_DEPTH 16
#define MEDIA_ENTITY_ENUM_MAX_ID 64
struct media_entity_graph {
struct {
struct media_entity *entity;
int link;
} stack[MEDIA_ENTITY_ENUM_MAX_DEPTH];
DECLARE_BITMAP(entities, MEDIA_ENTITY_ENUM_MAX_ID);
int top;
};