Hi Hans, On Wednesday 23 Mar 2016 15:57:10 Hans Verkuil wrote: > On 03/23/2016 03:45 PM, Laurent Pinchart wrote: > > On Wednesday 23 Mar 2016 15:05:41 Hans Verkuil wrote: > >> On 03/23/2016 11:35 AM, Mauro Carvalho Chehab wrote: > >>> Em Wed, 23 Mar 2016 10:45:55 +0200 Laurent Pinchart escreveu: > >>>> Code that processes media entities can require knowledge of the > >>>> structure type that embeds a particular media entity instance in order > >>>> to cast the entity to the proper object type. This needs is shown by > >>>> the presence of the is_media_entity_v4l2_io and > >>>> is_media_entity_v4l2_subdev functions. > >>>> > >>>> The implementation of those two functions relies on the entity function > >>>> field, which is both a wrong and an inefficient design, without even > >>>> mentioning the maintenance issue involved in updating the functions > >>>> every time a new entity function is added. Fix this by adding add an > >>>> obj_type field to the media entity structure to carry the information. > >>>> > >>>> Signed-off-by: Laurent Pinchart > >>>> <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx> > >>>> Acked-by: Hans Verkuil <hans.verkuil@xxxxxxxxx> > >>>> Acked-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx> > >>>> --- > >>>> > >>>> drivers/media/media-device.c | 2 + > >>>> drivers/media/v4l2-core/v4l2-dev.c | 1 + > >>>> drivers/media/v4l2-core/v4l2-subdev.c | 1 + > >>>> include/media/media-entity.h | 79 +++++++++++++++------------ > >>>> 4 files changed, 46 insertions(+), 37 deletions(-) > >>>> > >>>> diff --git a/drivers/media/media-device.c > >>>> b/drivers/media/media-device.c > >>>> index 4a97d92a7e7d..88d8de3b7a4f 100644 > >>>> --- a/drivers/media/media-device.c > >>>> +++ b/drivers/media/media-device.c > >>>> @@ -580,6 +580,8 @@ int __must_check > >>>> media_device_register_entity(struct > >>>> media_device *mdev, > >>>> "Entity type for entity %s was not initialized!\n", > >>>> entity->name); > >>>> > >>>> + WARN_ON(entity->obj_type == MEDIA_ENTITY_TYPE_INVALID); > >>>> + > >>> > >>> This is not ok. There are valid cases where the entity is not embedded > >>> on some other struct. That's the case of connectors/connections, for > >>> example: a connector/connection entity doesn't need anything else but > >>> struct media device. > >> > >> Once connectors are enabled, then we do need a > >> MEDIA_ENTITY_TYPE_CONNECTOR or MEDIA_ENTITY_TYPE_STANDALONE or something > >> along those lines. > > > > MEDIA_ENTITY_TYPE_CONNECTOR would make sense, but only if we add a struct > > media_connector. I believe that can be a good idea, at least to simplify > > management of the entity and the connector pad(s). > > > >>> Also, this is V4L2 specific. Neither ALSA nor DVB need to use > >>> container_of(). Actually, this won't even work there, as the entity is > >>> stored as a pointer, and not as an embedded data. > > > > That's sounds like a strange design decision at the very least. There can > > be valid cases that require creation of bare entities, but I don't think > > they should be that common. > > > >> Any other subsystem that *does* embed this can use obj_type. If it > >> doesn't embed it in anything, then MEDIA_ENTITY_TYPE_STANDALONE should be > >> used (or whatever name we give it). I agree that we need a type define > >> for the case where it is not embedded. > > > > I'd like to point out that I had defined MEDIA_ENTITY_TYPE_MEDIA_ENTITY > > for that purpose in v4, and was requested to drop it. > > I think MEDIA_ENTITY_TYPE_MEDIA_ENTITY is very ugly. Hm, some alternatives: > > MEDIA_ENTITY_TYPE_NONE > MEDIA_ENTITY_TYPE_ME > MEDIA_ENTITY_TYPE_SINGLETON > MEDIA_ENTITY_TYPE_BASE > > I personally prefer the last since it is just the media_entity base class by > itself. That's good because I don't like any of the first three :-) I'm OK with BASE. -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
