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Commit 5c7b25b9 authored by Laurent Pinchart's avatar Laurent Pinchart Committed by Mauro Carvalho Chehab
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[media] media: Add support for circular graph traversal 



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: default avatarLaurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: default avatarSakari Ailus <sakari.ailus@iki.fi>
Acked-by: default avatarHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: default avatarMauro Carvalho Chehab <m.chehab@samsung.com>
parent 3a967706

drivers/media/media-entity.c

+11 −3
Original line number Diff line number Diff line
@@ -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;

		}

include/media/media-entity.h

+4 −0
Original line number Diff line number Diff line
@@ -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;

};