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

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Hi Laurent,

On Wed, Jan 16, 2019 at 01:24:05AM +0200, Laurent Pinchart wrote:
> Hi Niklas,
> 
> Thank you for the patch.
> 
> 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.

> 
> > +}
> > +
> > +/**
> > + * 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.

> 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.
> >   *
> 

-- 
Sakari Ailus
sakari.ailus@linux.intel.com