Re: [PATCH v2 4/7] media: v4l2-subdev: Refactor warnings in v4l2_subdev_link_validate()

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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;





[Index of Archives]     [Linux Samsung SOC]     [Linux Wireless]     [Linux Kernel]     [ATH6KL]     [Linux Bluetooth]     [Linux Netdev]     [Kernel Newbies]     [IDE]     [Security]     [Git]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux ATA RAID]     [Samba]     [Device Mapper]

  Powered by Linux