| Message ID | 20240822154531.25912-6-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| State | Superseded |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() helper function is meant to be used as a > drop-in implementation of a V4L2 subdev entity .link_validate() handler. > It supports subdev-to-subdev links only, and complains if one end of the > link is not a subdev. This forces drivers that have video output devices > connected to subdevs to implement a custom .link_validate() handler, > calling v4l2_subdev_link_validate() for the subdev-to-subdev links, and > performing manual link validation for the video-to-subdev links. > > Video devices embed a media entity, and therefore also have a > .link_validate() operation. For video capture devices, the operation > should be manually implemented by drivers for validate the > subdev-to-video links. For video output devices, on the other hand, that > operation is never called, as link validation is performed in the > context of the sink entity. > > As a result, we end up forcing drivers to implement a custom > .link_validate() handler for subdevs connected to video output devices, > when the video devices provide an operation that could be used for that > purpose. > > To improve that situation, make v4l2_subdev_link_validate() delegate > link validation to the source's .link_validate() operation when the link > source is a video device and the link sink is a subdev. This allows > broader usage of v4l2_subdev_link_validate(), and simplifies drivers by > making video device link validation easy to implement in the video > device .link_validate(), regardless of whether the video device is an > output device or a capture device. Maybe mention this patch in the previous patch's desc to answer the question I sent =) > Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com> > --- > drivers/media/v4l2-core/v4l2-subdev.c | 40 +++++++++++++++++++++++---- > include/media/v4l2-subdev.h | 6 ++++ > 2 files changed, 41 insertions(+), 5 deletions(-) > > diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c > index d3196042d5c5..32ffebae4d17 100644 > --- a/drivers/media/v4l2-core/v4l2-subdev.c > +++ b/drivers/media/v4l2-core/v4l2-subdev.c > @@ -1450,13 +1450,43 @@ int v4l2_subdev_link_validate(struct media_link *link) > 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; > + /* > + * If the source is a video device, delegate link validation to it. This > + * allows usage of this helper for subdev connected to a video output > + * device, provided that the driver implement the video output device's > + * .link_validate() operation. > + */ > + if (is_media_entity_v4l2_video_device(link->source->entity)) { > + struct media_entity *source = link->source->entity; > + > + if (!source->ops || !source->ops->link_validate) { > + /* > + * Many existing drivers do not implement the required > + * .link_validate() operation for their video devices. > + * Print a warning to get the drivers fixed, and return > + * 0 to avoid breaking userspace. This should > + * eventually be turned into a WARN_ON() when all > + * drivers will have been fixed. > + */ > + pr_warn_once("video device '%s' does not implement .link_validate(), driver bug!\n", > + source->name); > + return 0; > + } > + > + /* Avoid infinite loops. */ Maybe this could elaborate a bit, and say that non-subdev drivers should not use v4l2_subdev_link_validate, but some do (?) or might use it by mistake, and this catches the driver bug. > + if (WARN_ON(source->ops->link_validate == v4l2_subdev_link_validate)) > + return -EINVAL; This might still be risky. The driver could implement its own validate, which does some checks and then calls v4l2_subdev_link_validate(). But I'm sure that'll get get noticed =). Tomi > + > + return source->ops->link_validate(link); > } > > + /* > + * If the source is still not a subdev, usage of this helper is a clear > + * driver bug. > + */ > + if (WARN_ON(!is_media_entity_v4l2_subdev(link->source->entity))) > + return -EINVAL; > + > sink_sd = media_entity_to_v4l2_subdev(link->sink->entity); > source_sd = media_entity_to_v4l2_subdev(link->source->entity); > > diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h > index bd235d325ff9..8daa0929865c 100644 > --- a/include/media/v4l2-subdev.h > +++ b/include/media/v4l2-subdev.h > @@ -1250,6 +1250,12 @@ int v4l2_subdev_link_validate_default(struct v4l2_subdev *sd, > * calls v4l2_subdev_link_validate_default() to ensure that > * width, height and the media bus pixel code are equal on both > * source and sink of the link. > + * > + * The function can be used as a drop-in &media_entity_ops.link_validate > + * implementation for v4l2_subdev instances. It supports all links between > + * subdevs, as well as links between subdevs and video devices, provided that > + * the video devices also implement their &media_entity_ops.link_validate > + * operation. > */ > int v4l2_subdev_link_validate(struct media_link *link); >
Hi Tomi, On Mon, Aug 26, 2024 at 02:23:06PM +0300, Tomi Valkeinen wrote: > On 22/08/2024 18:45, Laurent Pinchart wrote: > > The v4l2_subdev_link_validate() helper function is meant to be used as a > > drop-in implementation of a V4L2 subdev entity .link_validate() handler. > > It supports subdev-to-subdev links only, and complains if one end of the > > link is not a subdev. This forces drivers that have video output devices > > connected to subdevs to implement a custom .link_validate() handler, > > calling v4l2_subdev_link_validate() for the subdev-to-subdev links, and > > performing manual link validation for the video-to-subdev links. > > > > Video devices embed a media entity, and therefore also have a > > .link_validate() operation. For video capture devices, the operation > > should be manually implemented by drivers for validate the > > subdev-to-video links. For video output devices, on the other hand, that > > operation is never called, as link validation is performed in the > > context of the sink entity. > > > > As a result, we end up forcing drivers to implement a custom > > .link_validate() handler for subdevs connected to video output devices, > > when the video devices provide an operation that could be used for that > > purpose. > > > > To improve that situation, make v4l2_subdev_link_validate() delegate > > link validation to the source's .link_validate() operation when the link > > source is a video device and the link sink is a subdev. This allows > > broader usage of v4l2_subdev_link_validate(), and simplifies drivers by > > making video device link validation easy to implement in the video > > device .link_validate(), regardless of whether the video device is an > > output device or a capture device. > > Maybe mention this patch in the previous patch's desc to answer the > question I sent =) I'll do so. > > Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com> > > --- > > drivers/media/v4l2-core/v4l2-subdev.c | 40 +++++++++++++++++++++++---- > > include/media/v4l2-subdev.h | 6 ++++ > > 2 files changed, 41 insertions(+), 5 deletions(-) > > > > diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c > > index d3196042d5c5..32ffebae4d17 100644 > > --- a/drivers/media/v4l2-core/v4l2-subdev.c > > +++ b/drivers/media/v4l2-core/v4l2-subdev.c > > @@ -1450,13 +1450,43 @@ int v4l2_subdev_link_validate(struct media_link *link) > > 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; > > + /* > > + * If the source is a video device, delegate link validation to it. This > > + * allows usage of this helper for subdev connected to a video output > > + * device, provided that the driver implement the video output device's > > + * .link_validate() operation. > > + */ > > + if (is_media_entity_v4l2_video_device(link->source->entity)) { > > + struct media_entity *source = link->source->entity; > > + > > + if (!source->ops || !source->ops->link_validate) { > > + /* > > + * Many existing drivers do not implement the required > > + * .link_validate() operation for their video devices. > > + * Print a warning to get the drivers fixed, and return > > + * 0 to avoid breaking userspace. This should > > + * eventually be turned into a WARN_ON() when all > > + * drivers will have been fixed. > > + */ > > + pr_warn_once("video device '%s' does not implement .link_validate(), driver bug!\n", > > + source->name); > > + return 0; > > + } > > + > > + /* Avoid infinite loops. */ > > Maybe this could elaborate a bit, and say that non-subdev drivers should > not use v4l2_subdev_link_validate, but some do (?) or might use it by > mistake, and this catches the driver bug. I'll expand the comment to /* * Avoid infinite loops in case a video device incorrectly uses * this helper function as its .link_validate() handler. */ > > + if (WARN_ON(source->ops->link_validate == v4l2_subdev_link_validate)) > > + return -EINVAL; > > This might still be risky. The driver could implement its own validate, > which does some checks and then calls v4l2_subdev_link_validate(). But > I'm sure that'll get get noticed =). Yes, that would still lead to an infinite loop, but there's only so much we can do against foot-shooting. > > + > > + return source->ops->link_validate(link); > > } > > > > + /* > > + * If the source is still not a subdev, usage of this helper is a clear > > + * driver bug. > > + */ > > + if (WARN_ON(!is_media_entity_v4l2_subdev(link->source->entity))) > > + return -EINVAL; > > + > > sink_sd = media_entity_to_v4l2_subdev(link->sink->entity); > > source_sd = media_entity_to_v4l2_subdev(link->source->entity); > > > > diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h > > index bd235d325ff9..8daa0929865c 100644 > > --- a/include/media/v4l2-subdev.h > > +++ b/include/media/v4l2-subdev.h > > @@ -1250,6 +1250,12 @@ int v4l2_subdev_link_validate_default(struct v4l2_subdev *sd, > > * calls v4l2_subdev_link_validate_default() to ensure that > > * width, height and the media bus pixel code are equal on both > > * source and sink of the link. > > + * > > + * The function can be used as a drop-in &media_entity_ops.link_validate > > + * implementation for v4l2_subdev instances. It supports all links between > > + * subdevs, as well as links between subdevs and video devices, provided that > > + * the video devices also implement their &media_entity_ops.link_validate > > + * operation. > > */ > > int v4l2_subdev_link_validate(struct media_link *link); > >
diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c index d3196042d5c5..32ffebae4d17 100644 --- a/drivers/media/v4l2-core/v4l2-subdev.c +++ b/drivers/media/v4l2-core/v4l2-subdev.c @@ -1450,13 +1450,43 @@ int v4l2_subdev_link_validate(struct media_link *link) 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; + /* + * If the source is a video device, delegate link validation to it. This + * allows usage of this helper for subdev connected to a video output + * device, provided that the driver implement the video output device's + * .link_validate() operation. + */ + if (is_media_entity_v4l2_video_device(link->source->entity)) { + struct media_entity *source = link->source->entity; + + if (!source->ops || !source->ops->link_validate) { + /* + * Many existing drivers do not implement the required + * .link_validate() operation for their video devices. + * Print a warning to get the drivers fixed, and return + * 0 to avoid breaking userspace. This should + * eventually be turned into a WARN_ON() when all + * drivers will have been fixed. + */ + pr_warn_once("video device '%s' does not implement .link_validate(), driver bug!\n", + source->name); + return 0; + } + + /* Avoid infinite loops. */ + if (WARN_ON(source->ops->link_validate == v4l2_subdev_link_validate)) + return -EINVAL; + + return source->ops->link_validate(link); } + /* + * If the source is still not a subdev, usage of this helper is a clear + * driver bug. + */ + if (WARN_ON(!is_media_entity_v4l2_subdev(link->source->entity))) + return -EINVAL; + sink_sd = media_entity_to_v4l2_subdev(link->sink->entity); source_sd = media_entity_to_v4l2_subdev(link->source->entity); diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h index bd235d325ff9..8daa0929865c 100644 --- a/include/media/v4l2-subdev.h +++ b/include/media/v4l2-subdev.h @@ -1250,6 +1250,12 @@ int v4l2_subdev_link_validate_default(struct v4l2_subdev *sd, * calls v4l2_subdev_link_validate_default() to ensure that * width, height and the media bus pixel code are equal on both * source and sink of the link. + * + * The function can be used as a drop-in &media_entity_ops.link_validate + * implementation for v4l2_subdev instances. It supports all links between + * subdevs, as well as links between subdevs and video devices, provided that + * the video devices also implement their &media_entity_ops.link_validate + * operation. */ int v4l2_subdev_link_validate(struct media_link *link);
The v4l2_subdev_link_validate() helper function is meant to be used as a drop-in implementation of a V4L2 subdev entity .link_validate() handler. It supports subdev-to-subdev links only, and complains if one end of the link is not a subdev. This forces drivers that have video output devices connected to subdevs to implement a custom .link_validate() handler, calling v4l2_subdev_link_validate() for the subdev-to-subdev links, and performing manual link validation for the video-to-subdev links. Video devices embed a media entity, and therefore also have a .link_validate() operation. For video capture devices, the operation should be manually implemented by drivers for validate the subdev-to-video links. For video output devices, on the other hand, that operation is never called, as link validation is performed in the context of the sink entity. As a result, we end up forcing drivers to implement a custom .link_validate() handler for subdevs connected to video output devices, when the video devices provide an operation that could be used for that purpose. To improve that situation, make v4l2_subdev_link_validate() delegate link validation to the source's .link_validate() operation when the link source is a video device and the link sink is a subdev. This allows broader usage of v4l2_subdev_link_validate(), and simplifies drivers by making video device link validation easy to implement in the video device .link_validate(), regardless of whether the video device is an output device or a capture device. Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com> --- drivers/media/v4l2-core/v4l2-subdev.c | 40 +++++++++++++++++++++++---- include/media/v4l2-subdev.h | 6 ++++ 2 files changed, 41 insertions(+), 5 deletions(-)