Hi Mauro,
Thank you for the patch.
On Sunday 06 September 2015 14:30:47 Mauro Carvalho Chehab wrote:
> Due to the graph traversal algorithm currently in usage, we
> need a copy of all data links. Those backlinks should not be
> send to userspace, as otherwise, all links there will be
> duplicated.
>
> Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxx>
>
> diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
> index 0238885fcc74..97eb97d9b662 100644
> --- a/drivers/media/media-device.c
> +++ b/drivers/media/media-device.c
> @@ -333,6 +333,9 @@ static long __media_device_get_topology(struct
> media_device *mdev, /* Get links and number of links */
> i = 0;
> media_device_for_each_link(link, mdev) {
> + if (link->is_backlink)
> + continue;
> +
> i++;
>
> if (ret || !topo->links)
> diff --git a/drivers/media/media-entity.c b/drivers/media/media-entity.c
> index cd4d767644df..4868b8269204 100644
> --- a/drivers/media/media-entity.c
> +++ b/drivers/media/media-entity.c
> @@ -648,6 +648,7 @@ media_create_pad_link(struct media_entity *source, u16
> source_pad, backlink->source = &source->pads[source_pad];
> backlink->sink = &sink->pads[sink_pad];
> backlink->flags = flags;
> + backlink->is_backlink = true;
>
> /* Initialize graph object embedded at the new link */
> media_gobj_init(sink->graph_obj.mdev, MEDIA_GRAPH_LINK,
> diff --git a/include/media/media-entity.h b/include/media/media-entity.h
> index e1a89899deef..3d389f142a1d 100644
> --- a/include/media/media-entity.h
> +++ b/include/media/media-entity.h
> @@ -96,6 +96,7 @@ struct media_pipeline {
> * @reverse: Pointer to the link for the reverse direction of a pad to
pad
> * link.
> * @flags: Link flags, as defined at uapi/media.h (MEDIA_LNK_FL_*)
> + * @is_backlink: Indicate if the link is a backlink.
> */
> struct media_link {
> struct media_gobj graph_obj;
> @@ -112,6 +113,7 @@ struct media_link {
> };
> struct media_link *reverse;
> unsigned long flags;
> + bool is_backlink;
I agree with the purpose of this patch (and as stated for other patches in the
series I believe you should squash it with the patch that introduces the
G_TOPOLOGY ioctl) but I won't whether you couldn't do with the additional
variable by adding a flag for backlinks (flag that wouldn't be shown to
userspace).
Now that I think about it an even better implementation could be to avoid
creating backlinks at all. As links are now dynamically allocated you could
have two struct list_head in the link structure, one for the source and one
for the sink. It sounds too easy to be true, I wonder if I'm overlooking
something.
> };
>
> /**
--
Regards,
Laurent Pinchart
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