Hi Laurent,
On Wed, Aug 21, 2013 at 05:22:45AM +0200, Laurent Pinchart wrote:
> Hi Sakari,
>
> On Saturday 10 August 2013 15:16:29 Sakari Ailus wrote:
> > On Fri, Aug 09, 2013 at 01:34:46AM +0200, Laurent Pinchart wrote:
> > > On Friday 19 July 2013 20:55:07 Sakari Ailus wrote:
> > > > Do not allow streaming if a pad with MEDIA_PAD_FL_MUST_CONNECT flag is
> > > > not connected by an active link.
> > > >
> > > > This patch makes it possible to avoid drivers having to check for the
> > > > most common case of link state validation: a sink pad that must be
> > > > connected.
> > > >
> > > > Signed-off-by: Sakari Ailus <sakari.ai...@iki.fi>
> > > > ---
> > > >
> > > > drivers/media/media-entity.c | 34 +++++++++++++++++++++++++++-------
> > > > 1 file changed, 27 insertions(+), 7 deletions(-)
> > > >
> > > > diff --git a/drivers/media/media-entity.c b/drivers/media/media-entity.c
> > > > index cb30ffb..4e58f8a 100644
> > > > --- a/drivers/media/media-entity.c
> > > > +++ b/drivers/media/media-entity.c
> > > > @@ -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>
> > > > @@ -227,6 +228,7 @@ __must_check int media_entity_pipeline_start(struct
> > > > media_entity *entity,
> > > > media_entity_graph_walk_start(&graph, entity);
> > > >
> > > > while ((entity = media_entity_graph_walk_next(&graph))) {
> > > > + DECLARE_BITMAP(active, entity->num_pads);
> > > > unsigned int i;
> > > >
> > > > entity->stream_count++;
> > > >
> > > > @@ -240,21 +242,39 @@ __must_check int
> > > > media_entity_pipeline_start(struct media_entity *entity,
> > > > if (!entity->ops || !entity->ops->link_validate)
> > > > continue;
> > > >
> > > > + bitmap_zero(active, entity->num_pads);
> > > > +
> > > > for (i = 0; i < entity->num_links; i++) {
> > > > struct media_link *link = &entity->links[i];
> > > > -
> > > > - /* Is this pad part of an enabled link? */
> > > > - if (!(link->flags & MEDIA_LNK_FL_ENABLED))
> > > > - continue;
> > > > -
> > > > - /* Are we the sink or not? */
> > > > - if (link->sink->entity != entity)
> > > > + struct media_pad *pad = link->sink->entity ==
> > > > entity
> > > > + ? link->sink : link->source;
> > > > +
> > > > + /*
> > > > + * Pads that either do not need to connect or
> > > > + * are connected through an enabled link are
> > > > + * fine.
> > > > + */
> > > > + if (!(pad->flags & MEDIA_PAD_FL_MUST_CONNECT)
> > > > + || link->flags & MEDIA_LNK_FL_ENABLED)
> > > > + bitmap_set(active, pad->index, 1);
> > > > +
> > > > + /*
> > > > + * Link validation will only take place for
> > > > + * sink ends of the link that are enabled.
> > > > + */
> > > > + if (link->sink != pad
> > > > + || !(link->flags & MEDIA_LNK_FL_ENABLED))
> > > > continue;
> > > >
> > > > ret = entity->ops->link_validate(link);
> > > > if (ret < 0 && ret != -ENOIOCTLCMD)
> > > > goto error;
> > > > }
> > > > +
> > > > + if (!bitmap_full(active, entity->num_pads)) {
> > > > + ret = -EPIPE;
> > > > + goto error;
> > > > + }
> > >
> > > I'm afraid that won't work if one of the pads has no links. In that case
> > > the bitmap won't be full. I think you will have to iterate separately on
> > > the links to validate them, and on the pads to check the flags.
> >
> > Good point.
> >
> > I could as well add another bitmap or perhaps rather keep the information in
> > struct media_pad, separately from flags since this is something the user can
> > find through other means --- that way we don't add practically any runtime
> > overhead.
> >
> > What do you think?
>
> Given the number of pads we expect on an entity, is it really worth the micro-
> optimization ? I think I would just loop over the links and pads separately,
> especially given that you need to validate pads even if the entity has no
> link_validate operation, which is checked before the for loop over the links.
I'm fine with that. Even if the information was kept in struct media_pad, a
loop would be needed to dig it out. Alternatively a bitmap could be put to
struct media_entity but that'd be less pretty.
I'll just add another bitmap here. It can later be moved to struct
media_entity if needed.
--
Cheers,
Sakari Ailus
e-mail: sakari.ai...@iki.fi XMPP: sai...@retiisi.org.uk
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