Re: [PATCH v2 12/30] media: entity: Add an iterator helper for connected pads

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Sakari,

On Tue, Jan 22, 2019 at 05:36:55PM +0200, Sakari Ailus wrote:
> On Wed, Jan 16, 2019 at 01:24:05AM +0200, Laurent Pinchart wrote:
> > On Fri, Nov 02, 2018 at 12:31:26AM +0100, Niklas Söderlund wrote:
> >> From: Sakari Ailus <sakari.ailus@linux.intel.com>
> >> 
> >> Add a helper macro for iterating over pads that are connected through
> >> enabled routes. This can be used to find all the connected pads within an
> >> entity, for instance starting from the pad which has been obtained during
> >> the graph walk.
> >> 
> >> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> >> Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> >> ---
> >>  include/media/media-entity.h | 27 +++++++++++++++++++++++++++
> >>  1 file changed, 27 insertions(+)
> >> 
> >> diff --git a/include/media/media-entity.h b/include/media/media-entity.h
> >> index 9540d2af80f19805..4bb1b568e1ac4795 100644
> >> --- a/include/media/media-entity.h
> >> +++ b/include/media/media-entity.h
> >> @@ -936,6 +936,33 @@ __must_check int media_graph_walk_init(
> >>  bool media_entity_has_route(struct media_entity *entity, unsigned int pad0,
> >>  			    unsigned int pad1);
> >>  
> >> +static inline struct media_pad *__media_entity_for_routed_pads_next(
> >> +	struct media_pad *start, struct media_pad *iter)
> >> +{
> >> +	struct media_entity *entity = start->entity;
> >> +
> >> +	while (iter < &entity->pads[entity->num_pads] &&
> >> +	       !media_entity_has_route(entity, start->index, iter->index))
> >> +		iter++;
> >> +
> >> +	return iter;
> > 
> > Returning a pointer past the end of the array is asking for trouble. I
> > think we should return NULL in that case, and adapt the check in
> > media_entity_for_routed_pads() accordingly.
> 
> Well, that pointer never gets used, in a similar manner than simply looping
> over an array. I wouldn't change that --- this function is also integrally
> a part of media_entity_for_each_routed_pad() implementation below.

I know it doesn't get used, but it's still asking for trouble, it will
be easy to use it by mistake. Returning NULL would be clearer.

> >> +}
> >> +
> >> +/**
> >> + * media_entity_for_routed_pads - Iterate over entity pads connected by routes
> >> + *
> >> + * @start: The stating pad
> > 
> > s/stating/starting/
> > 
> >> + * @iter: The iterator pad
> >> + *
> >> + * Iterate over all pads connected through routes from a given pad
> >> + * within an entity. The iteration will include the starting pad itself.
> >> + */
> >> +#define media_entity_for_routed_pads(start, iter)			\
> > 
> > Maybe media_entity_for_each_routed_pad() ? Or just
> 
> I'd prefer this one: we have media_entity_ prefix for pretty much
> everything that handles entities.

It's a bit long, but OK.

> > for_each_entity_routed_pad() ?
> > 
> >> +	for (iter = __media_entity_for_routed_pads_next(		\
> > 
> > And how about __media_entity_next_routed_pad() ?
> 
> Yes.
> 
> > 
> >> +		     start, (start)->entity->pads);			\
> >> +	     iter < &(start)->entity->pads[(start)->entity->num_pads];	\
> >> +	     iter = __media_entity_for_routed_pads_next(start, iter + 1))
> >> +
> >>  /**
> >>   * media_graph_walk_cleanup - Release resources used by graph walk.
> >>   *

-- 
Regards,

Laurent Pinchart