Hi,
On 22/08/2024 18:45, Laurent Pinchart wrote:
The v4l2_subdev_link_validate() function prints a one-time warning if it
gets called on a link whose source or sink is not a subdev. As links get
validated in the context of their sink, a call to the helper when the
link's sink is not a subdev indicates that the driver has set its
.link_validate() handler to v4l2_subdev_link_validate() on a non-subdev
entity, which is a clear driver bug. On the other hand, the link's
source not being a subdev indicates that the helper is used for a subdev
connected to a video output device, which is a lesser issue, if only
because this is currently common practice.
Hmm, what does this mean... So we have a sink subdev, which might be
linked to a source subdev (in which case everything is fine), or it
might be linked to a non-subdev source.
Why is it a bug to be linked to a non-subdev source? And if it is a bug,
why is ok (only pr_warn_once)?
Tomi
There are no drivers left in the kernel that use
v4l2_subdev_link_validate() in a context where it may get called on a
non-subdev sink. Replace the pr_warn_once() with a WARN_ON_ONCE() in
this case to make sure that new offenders won't be introduced.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx>
---
Changes since v1:
- Switch from WARN_ON() to WARN_ON_ONCE()
---
drivers/media/v4l2-core/v4l2-subdev.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 7c5812d55315..d3196042d5c5 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -1443,11 +1443,15 @@ int v4l2_subdev_link_validate(struct media_link *link)
bool states_locked;
int ret;
- if (!is_media_entity_v4l2_subdev(link->sink->entity) ||
- !is_media_entity_v4l2_subdev(link->source->entity)) {
- pr_warn_once("%s of link '%s':%u->'%s':%u is not a V4L2 sub-device, driver bug!\n",
- !is_media_entity_v4l2_subdev(link->sink->entity) ?
- "sink" : "source",
+ /*
+ * Links are validated in the context of the sink entity. Usage of this
+ * helper on a sink that is not a subdev is a clear driver bug.
+ */
+ if (WARN_ON_ONCE(!is_media_entity_v4l2_subdev(link->sink->entity)))
+ return -EINVAL;
+
+ if (!is_media_entity_v4l2_subdev(link->source->entity)) {
+ pr_warn_once("source of link '%s':%u->'%s':%u is not a V4L2 sub-device, driver bug!\n",
link->source->entity->name, link->source->index,
link->sink->entity->name, link->sink->index);
return 0;
