Em Fri, 4 Mar 2016 22:18:50 +0200
Laurent Pinchart <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx> 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,
I agree with Sakari here: it is not wrong, just risky when new types
are added.
Btw, I still don't like using "type" here. People that didn't read
all those boring MC discussions will be confused, as we're removing
"type" in one version, and re-introducing it again with a very
different meaning.
What we're really doing here is to "flag" when the entity is a subdev
or when the entity is a V4L I/O entity. Also, one thing that bothers me
is that this is very subsystem-specific. See more below.
> without even
> mentioning the maintenance issue involved in updating the functions
> every time a new entity function is added. Fix this by adding add a 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>
> ---
> drivers/media/v4l2-core/v4l2-dev.c | 1 +
> drivers/media/v4l2-core/v4l2-subdev.c | 1 +
> include/media/media-entity.h | 75 ++++++++++++++++++-----------------
> 3 files changed, 40 insertions(+), 37 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
> index d8e5994cccf1..7e766a92e3d9 100644
> --- a/drivers/media/v4l2-core/v4l2-dev.c
> +++ b/drivers/media/v4l2-core/v4l2-dev.c
> @@ -735,6 +735,7 @@ static int video_register_media_controller(struct video_device *vdev, int type)
> if (!vdev->v4l2_dev->mdev)
> return 0;
>
> + vdev->entity.type = MEDIA_ENTITY_TYPE_VIDEO_DEVICE;
> vdev->entity.function = MEDIA_ENT_F_UNKNOWN;
>
> switch (type) {
> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> index d63083803144..bb6e79f14bb8 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -584,6 +584,7 @@ void v4l2_subdev_init(struct v4l2_subdev *sd, const struct v4l2_subdev_ops *ops)
> sd->host_priv = NULL;
> #if defined(CONFIG_MEDIA_CONTROLLER)
> sd->entity.name = sd->name;
> + sd->entity.type = MEDIA_ENTITY_TYPE_V4L2_SUBDEV;
> sd->entity.function = MEDIA_ENT_F_V4L2_SUBDEV_UNKNOWN;
> #endif
> }
> diff --git a/include/media/media-entity.h b/include/media/media-entity.h
> index 6dc9e4e8cbd4..d148fc49c3be 100644
> --- a/include/media/media-entity.h
> +++ b/include/media/media-entity.h
> @@ -188,10 +188,37 @@ struct media_entity_operations {
> };
>
> /**
> + * enum media_entity_type - Media entity type
> + *
> + * @MEDIA_ENTITY_TYPE_MEDIA_ENTITY:
> + * The entity is a struct media_entity instance.
All entities are a media_entity instance. This doesn't make sense!
> + * @MEDIA_ENTITY_TYPE_VIDEO_DEVICE:
> + * The entity is a struct video_device instance.
> + * @MEDIA_ENTITY_TYPE_V4L2_SUBDEV:
> + * The entity is a struct v4l2_subdev instance.
> + *
> + * The entity type identifies the type of the object instance that implements
> + * the struct media_entity instance. This allows runtime type identification of
> + * media entities and safe casting to the project object type. For instance, a
> + * media entity structure instance embedded in a v4l2_subdev structure instance
> + * will have the type MEDIA_ENTITY_TYPE_V4L2_SUBDEV and can safely be cast to a
> + * v4l2_subdev structure using the container_of() macro.
> + *
> + * Media entities can be instantiated without creating any derived object type,
> + * in which case their type will be MEDIA_ENTITY_TYPE_MEDIA_ENTITY.
> + */
> +enum media_entity_type {
> + MEDIA_ENTITY_TYPE_MEDIA_ENTITY,
> + MEDIA_ENTITY_TYPE_VIDEO_DEVICE,
> + MEDIA_ENTITY_TYPE_V4L2_SUBDEV,
> +};
> +
> +/**
> * struct media_entity - A media entity graph object.
> *
> * @graph_obj: Embedded structure containing the media object common data.
> * @name: Entity name.
> + * @type: Type of the object that implements the media_entity.
> * @function: Entity main function, as defined in uapi/media.h
> * (MEDIA_ENT_F_*)
> * @flags: Entity flags, as defined in uapi/media.h (MEDIA_ENT_FL_*)
> @@ -220,6 +247,7 @@ struct media_entity_operations {
> struct media_entity {
> struct media_gobj graph_obj; /* must be first field in struct */
> const char *name;
> + enum media_entity_type type;
> u32 function;
> unsigned long flags;
>
> @@ -329,56 +357,29 @@ static inline u32 media_gobj_gen_id(enum media_gobj_type type, u64 local_id)
> }
>
> /**
> - * is_media_entity_v4l2_io() - identify if the entity main function
> - * is a V4L2 I/O
> - *
> + * is_media_entity_v4l2_io() - Check if the entity is a video_device
> * @entity: pointer to entity
> *
> - * Return: true if the entity main function is one of the V4L2 I/O types
> - * (video, VBI or SDR radio); false otherwise.
> + * Return: true if the entity is an instance of a video_device object and can
> + * safely be cast to a struct video_device using the container_of() macro, or
> + * false otherwise.
> */
> static inline bool is_media_entity_v4l2_io(struct media_entity *entity)
> {
> - if (!entity)
> - return false;
> -
> - switch (entity->function) {
> - case MEDIA_ENT_F_IO_V4L:
> - case MEDIA_ENT_F_IO_VBI:
> - case MEDIA_ENT_F_IO_SWRADIO:
> - return true;
> - default:
> - return false;
> - }
> + return entity && entity->type == MEDIA_ENTITY_TYPE_VIDEO_DEVICE;
> }
>
> /**
> - * is_media_entity_v4l2_subdev - return true if the entity main function is
> - * associated with the V4L2 API subdev usage
> - *
> + * is_media_entity_v4l2_subdev() - Check if the entity is a v4l2_subdev
> * @entity: pointer to entity
> *
> - * This is an ancillary function used by subdev-based V4L2 drivers.
> - * It checks if the entity function is one of functions used by a V4L2 subdev,
> - * e. g. camera-relatef functions, analog TV decoder, TV tuner, V4L2 DSPs.
> + * Return: true if the entity is an instance of a v4l2_subdev object and can
> + * safely be cast to a struct v4l2_subdev using the container_of() macro, or
> + * false otherwise.
> */
> static inline bool is_media_entity_v4l2_subdev(struct media_entity *entity)
> {
> - if (!entity)
> - return false;
> -
> - switch (entity->function) {
> - case MEDIA_ENT_F_V4L2_SUBDEV_UNKNOWN:
> - case MEDIA_ENT_F_CAM_SENSOR:
> - case MEDIA_ENT_F_FLASH:
> - case MEDIA_ENT_F_LENS:
> - case MEDIA_ENT_F_ATV_DECODER:
> - case MEDIA_ENT_F_TUNER:
> - return true;
> -
> - default:
> - return false;
> - }
> + return entity && entity->type == MEDIA_ENTITY_TYPE_V4L2_SUBDEV;
> }
>
> /**
When I wrote the ENUM_ENTITIES compat code and deciding what would
be the best approach, it occurred to me that, for us to be able to
remove major,minor from entity, the best way would be to "taint"
the entities that have a 1:1 map with an interface, like:
- I/O nodes;
- subdevs (when CONFIG_VIDEO_V4L2_SUBDEV_API=y);
- ALSA mixer.
So, I was actually thinking that, instead of entity-type, we should
an internal flag to mark those internal "caps" attributes.
So, I guess we should really call this as entity->taint, entity->quirk
or entity->internal_flag or entity->caps instead. For now, I'll call
it "caps".
by adding "caps", this field can be a way more flexible, and may
be used for the needs on other subsystems too.
By implementing it as a "caps" flag, the part of the code at
media_device_enum_entities() on a patch dropping major and
minor from struct media_entity would be like:
if (ent->caps & ENTITY_HAS_DEVNODE) {
media_device_for_each_link(link, mdev) {
if (link->sink == ent) {
struct media_intf_devnode *devnode;
devnode = intf_to_devnode(intf);
u_ent.dev.major = devnode->major;
u_ent.dev.minor = devnode->minor;
}
}
}
This will also remove the need of touching at
video_register_media_controller(), with seems pretty much useless
so far. Just v4l2_subdev_init() will set "caps" to:
ENTITY_IS_V4L2_SUBDEV
Regards,
Mauro
PS.: patches 1 and 2 of this series are OK. I applied them
already.
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