Hi Laurent,
Many thanks for working on this.
On Mon, Jan 15, 2024 at 12:30:28PM +0200, Laurent Pinchart wrote:
> The MEDIA_PAD_FL_MUST_CONNECT flag indicates that the pad requires an
> enabled link to stream, but only if it has any link at all. This makes
> little sense, as if a pad is part of a pipeline, there are very few use
> cases for an active link to be mandatory only if links exist at all. A
> review of in-tree drivers confirms they all need an enabled link for
> pads marked with the MEDIA_PAD_FL_MUST_CONNECT flag.
>
> Expand the scope of the flag by rejecting pads that have no links at
> all. This requires modifying the pipeline build code to add those pads
> to the pipeline.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> ---
> .../media/mediactl/media-types.rst | 11 ++--
> drivers/media/mc/mc-entity.c | 53 +++++++++++++++----
> 2 files changed, 48 insertions(+), 16 deletions(-)
>
> diff --git a/Documentation/userspace-api/media/mediactl/media-types.rst b/Documentation/userspace-api/media/mediactl/media-types.rst
> index 0ffeece1e0c8..1ce87c0b705f 100644
> --- a/Documentation/userspace-api/media/mediactl/media-types.rst
> +++ b/Documentation/userspace-api/media/mediactl/media-types.rst
> @@ -375,12 +375,11 @@ Types and flags used to represent the media graph elements
> are origins of links.
>
> * - ``MEDIA_PAD_FL_MUST_CONNECT``
> - - If this flag is set and the pad is linked to any other pad, then
> - at least one of those links must be enabled for the entity to be
> - able to stream. There could be temporary reasons (e.g. device
> - configuration dependent) for the pad to need enabled links even
> - when this flag isn't set; the absence of the flag doesn't imply
> - there is none.
> + - If this flag, then at least one link connected to the pad must be
> + enabled for the pad to be able to stream. There could be temporary
> + reasons (e.g. device configuration dependent) for the pad to need
> + enabled links even when this flag isn't set; the absence of the flag
> + doesn't imply there is none.
Shoudln't you indent by tabs first here?
Would it be possible to backport this, too? I'm pretty sure there will be
NULL pointer dereferences due to this, even previous to the graph walk
rework.
It may require reworking this to apply it to the pre-rework implementation
and that's outside the scope of this set obviously.
For the set:
Acked-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
>
>
> One and only one of ``MEDIA_PAD_FL_SINK`` and ``MEDIA_PAD_FL_SOURCE``
> diff --git a/drivers/media/mc/mc-entity.c b/drivers/media/mc/mc-entity.c
> index 5907925ffd89..0e28b9a7936e 100644
> --- a/drivers/media/mc/mc-entity.c
> +++ b/drivers/media/mc/mc-entity.c
> @@ -535,14 +535,15 @@ static int media_pipeline_walk_push(struct media_pipeline_walk *walk,
>
> /*
> * Move the top entry link cursor to the next link. If all links of the entry
> - * have been visited, pop the entry itself.
> + * have been visited, pop the entry itself. Return true if the entry has been
> + * popped.
> */
> -static void media_pipeline_walk_pop(struct media_pipeline_walk *walk)
> +static bool media_pipeline_walk_pop(struct media_pipeline_walk *walk)
> {
> struct media_pipeline_walk_entry *entry;
>
> if (WARN_ON(walk->stack.top < 0))
> - return;
> + return false;
>
> entry = media_pipeline_walk_top(walk);
>
> @@ -552,7 +553,7 @@ static void media_pipeline_walk_pop(struct media_pipeline_walk *walk)
> walk->stack.top);
>
> walk->stack.top--;
> - return;
> + return true;
> }
>
> entry->links = entry->links->next;
> @@ -560,6 +561,8 @@ static void media_pipeline_walk_pop(struct media_pipeline_walk *walk)
> dev_dbg(walk->mdev->dev,
> "media pipeline: moved entry %u to next link\n",
> walk->stack.top);
> +
> + return false;
> }
>
> /* Free all memory allocated while walking the pipeline. */
> @@ -609,11 +612,12 @@ static int media_pipeline_explore_next_link(struct media_pipeline *pipe,
> struct media_link *link;
> struct media_pad *local;
> struct media_pad *remote;
> + bool last_link;
> int ret;
>
> origin = entry->pad;
> link = list_entry(entry->links, typeof(*link), list);
> - media_pipeline_walk_pop(walk);
> + last_link = media_pipeline_walk_pop(walk);
>
> dev_dbg(walk->mdev->dev,
> "media pipeline: exploring link '%s':%u -> '%s':%u\n",
> @@ -638,7 +642,7 @@ static int media_pipeline_explore_next_link(struct media_pipeline *pipe,
> local->index)) {
> dev_dbg(walk->mdev->dev,
> "media pipeline: skipping link (no route)\n");
> - return 0;
> + goto done;
> }
>
> /*
> @@ -653,13 +657,44 @@ static int media_pipeline_explore_next_link(struct media_pipeline *pipe,
> if (!(link->flags & MEDIA_LNK_FL_ENABLED)) {
> dev_dbg(walk->mdev->dev,
> "media pipeline: skipping link (disabled)\n");
> - return 0;
> + goto done;
> }
>
> ret = media_pipeline_add_pad(pipe, walk, remote);
> if (ret)
> return ret;
>
> +done:
> + /*
> + * If we're done iterating over links, iterate over pads of the entity.
> + * This is necessary to discover pads that are not connected with any
> + * link. Those are dead ends from a pipeline exploration point of view,
> + * but are still part of the pipeline and need to be added to enable
> + * proper validation.
> + */
> + if (!last_link)
> + return 0;
> +
> + dev_dbg(walk->mdev->dev,
> + "media pipeline: adding unconnected pads of '%s'\n",
> + local->entity->name);
> +
> + media_entity_for_each_pad(origin->entity, local) {
> + /*
> + * Skip the origin pad (already handled), pad that have links
> + * (already discovered through iterating over links) and pads
> + * not internally connected.
> + */
> + if (origin == local || !local->num_links ||
> + !media_entity_has_pad_interdep(origin->entity, origin->index,
> + local->index))
> + continue;
> +
> + ret = media_pipeline_add_pad(pipe, walk, local);
> + if (ret)
> + return ret;
> + }
> +
> return 0;
> }
>
> @@ -771,7 +806,6 @@ __must_check int __media_pipeline_start(struct media_pad *pad,
> struct media_pad *pad = ppad->pad;
> struct media_entity *entity = pad->entity;
> bool has_enabled_link = false;
> - bool has_link = false;
> struct media_link *link;
>
> dev_dbg(mdev->dev, "Validating pad '%s':%u\n", pad->entity->name,
> @@ -801,7 +835,6 @@ __must_check int __media_pipeline_start(struct media_pad *pad,
> /* Record if the pad has links and enabled links. */
> if (link->flags & MEDIA_LNK_FL_ENABLED)
> has_enabled_link = true;
> - has_link = true;
>
> /*
> * Validate the link if it's enabled and has the
> @@ -839,7 +872,7 @@ __must_check int __media_pipeline_start(struct media_pad *pad,
> * 3. If the pad has the MEDIA_PAD_FL_MUST_CONNECT flag set,
> * ensure that it has either no link or an enabled link.
> */
> - if ((pad->flags & MEDIA_PAD_FL_MUST_CONNECT) && has_link &&
> + if ((pad->flags & MEDIA_PAD_FL_MUST_CONNECT) &&
> !has_enabled_link) {
> dev_dbg(mdev->dev,
> "Pad '%s':%u must be connected by an enabled link\n",
--
Regards,
Sakari Ailus
