On 03/23/2016 03:45 PM, Laurent Pinchart wrote: > Hi Hans, > > 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. Regards, Hans -- 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
