Re: [PATCH RFC v3 02/16] media: Add a common embeed struct for all media graph objects

[Hans Verkuil <hverkuil@xs4all.nl>]

On 08/14/2015 03:21 PM, Mauro Carvalho Chehab wrote:
> Em Fri, 14 Aug 2015 16:08:34 +0300
> Sakari Ailus <sakari.ailus@iki.fi> escreveu:
> 
>> Hi Mauro,
>>
>> Thank you for the patchset!
>>
>> On Wed, Aug 12, 2015 at 05:14:46PM -0300, Mauro Carvalho Chehab wrote:
>>> Due to the MC API proposed changes, we'll need to:
>>> 	- have an unique object ID for all graph objects;
>>> 	- be able to dynamically create/remove objects;
>>> 	- be able to group objects;
>>> 	- keep the object in memory until we stop use it.
>>>
>>> Due to that, create a struct media_graph_obj and put there the
>>> common elements that all media objects will have in common.
>>>
>>> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
>>>
>>> diff --git a/include/media/media-entity.h b/include/media/media-entity.h
>>> index 0c003d817493..051aa3f8bbfe 100644
>>> --- a/include/media/media-entity.h
>>> +++ b/include/media/media-entity.h
>>> @@ -28,10 +28,50 @@
>>>  #include <linux/list.h>
>>>  #include <linux/media.h>
>>>  
>>> +/* Enums used internally at the media controller to represent graphs */
>>> +
>>> +/**
>>> + * enum media_graph_type - type of a graph element
>>> + *
>>> + * @MEDIA_GRAPH_ENTITY:		Identify a media entity
>>> + * @MEDIA_GRAPH_PAD:		Identify a media PAD
>>> + * @MEDIA_GRAPH_LINK:		Identify a media link
>>> + */
>>> +enum media_graph_type {
>>> +	MEDIA_GRAPH_ENTITY,
>>> +	MEDIA_GRAPH_PAD,
>>> +	MEDIA_GRAPH_LINK,
>>> +};
>>> +
>>> +
>>> +/* Structs to represent the objects that belong to a media graph */
>>> +
>>> +/**
>>> + * struct media_graph_obj - Define a graph object.
>>> + *
>>> + * @list:		List of media graph objects
>>> + * @obj_id:		Non-zero object ID identifier. The ID should be unique
>>> + *			inside a media_device
>>> + * @type:		Type of the graph object
>>> + * @mdev:		Media device that contains the object
>>> + *			object before stopping using it
>>> + *
>>> + * All elements on the media graph should have this struct embedded
>>> + */
>>> +struct media_graph_obj {
>>> +	struct list_head	list;
>>> +	struct list_head	group;
>>
>> What's group for?
> 
> I'm actually thinking on replacing group_id by a group list object type.
> 
> Anyway, I'm simplifying this patch series. So, I'll drop this field
> for now. We can add it when needed.
> 
>>
>>> +	u32			obj_id;
>>
>> I'd just call this "id".
> 
> OK.
> 
>>
>>> +	enum media_graph_type	type;
>>> +	struct media_device	*mdev;
>>> +};
>>> +
>>> +
>>>  struct media_pipeline {
>>>  };
>>>  
>>>  struct media_link {
>>> +	struct media_graph_obj			graph_obj;
>>>  	struct media_pad *source;	/* Source pad */
>>>  	struct media_pad *sink;		/* Sink pad  */
>>>  	struct media_link *reverse;	/* Link in the reverse direction */
>>> @@ -39,6 +79,7 @@ struct media_link {
>>>  };
>>>  
>>>  struct media_pad {
>>> +	struct media_graph_obj			graph_obj;
>>>  	struct media_entity *entity;	/* Entity this pad belongs to */
>>>  	u16 index;			/* Pad index in the entity pads array */
>>>  	unsigned long flags;		/* Pad flags (MEDIA_PAD_FL_*) */
>>> @@ -61,6 +102,7 @@ struct media_entity_operations {
>>>  };
>>>  
>>>  struct media_entity {
>>> +	struct media_graph_obj			graph_obj;
>>>  	struct list_head list;
>>>  	struct media_device *parent;	/* Media device this entity belongs to*/
>>>  	u32 id;				/* Entity ID, unique in the parent media
>>
>> Will entity id be different from the media_graph_obj obj_id of the object?
> 
> No. I'm right now writing a patch removing entity->id.

Oh good, I had the same thoughts as Sakari but forgot to write it down. I agree
with the changes you're making (remove group, rename obj_id to id and use it
instead of entity->id).

Regards,

	Hans