| Message ID | 20240822154531.25912-5-laurent.pinchart+renesas@ideasonboard.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Kieran Bingham |
| Headers | show |
| Series | media: v4l2: Improve media link validation | expand |
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@ideasonboard.com> > --- > 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;
Hi Tomi, On Mon, Aug 26, 2024 at 02:10:57PM +0300, Tomi Valkeinen wrote: > 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)? > > > 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. I'll add here A subsequent change will improve the v4l2_subdev_link_validate() helper to properly support validating video device to subdev links. > > > > Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com> > > --- > > 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;
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;
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. 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@ideasonboard.com> --- 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(-)