[libcamera-devel] [PATCH v2 3/4] libcamera: Add link handling functions

[Jacopo Mondi]

Add a function to the MediaLink class to set the state of a link to
enabled or disabled. The function makes use of an internal MediaDevice
method, which is defined private and only accessible by the MediaLink
setEnable() function itself.

Also add to MediaDevice a function to reset all links registered in the
media graph.

Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
---
v1->v2:
- Add resetLinks() function
- s/enable()/setEnable()
- s/setLink()/setupLink()
- Pass MediaLink and not two MediaPads to MediaDevice::setupLink

 src/libcamera/include/media_device.h |  4 ++
 src/libcamera/include/media_object.h |  1 +
 src/libcamera/media_device.cpp       | 75 ++++++++++++++++++++++++++++
 src/libcamera/media_object.cpp       | 29 +++++++++++
 4 files changed, 109 insertions(+)

diff --git a/src/libcamera/include/media_device.h b/src/libcamera/include/media_device.h
index 397d349..0f423aa 100644
--- a/src/libcamera/include/media_device.h
+++ b/src/libcamera/include/media_device.h
@@ -45,6 +45,7 @@ public:
 	MediaLink *link(const MediaEntity *source, unsigned int sourceIdx,
 			const MediaEntity *sink, unsigned int sinkIdx);
 	MediaLink *link(const MediaPad *source, const MediaPad *sink);
+	int resetLinks();

 private:
 	std::string driver_;
@@ -65,6 +66,9 @@ private:
 	bool populateEntities(const struct media_v2_topology &topology);
 	bool populatePads(const struct media_v2_topology &topology);
 	bool populateLinks(const struct media_v2_topology &topology);
+
+	friend int MediaLink::setEnable(bool enable);
+	int setupLink(const MediaLink *link, unsigned int flags);
 };

 } /* namespace libcamera */
diff --git a/src/libcamera/include/media_object.h b/src/libcamera/include/media_object.h
index d92aab3..bb46fac 100644
--- a/src/libcamera/include/media_object.h
+++ b/src/libcamera/include/media_object.h
@@ -41,6 +41,7 @@ public:
 	MediaPad *source() const { return source_; }
 	MediaPad *sink() const { return sink_; }
 	unsigned int flags() const { return flags_; }
+	int setEnable(bool enable);

 private:
 	friend class MediaDevice;
diff --git a/src/libcamera/media_device.cpp b/src/libcamera/media_device.cpp
index 7ce5c22..9900c3f 100644
--- a/src/libcamera/media_device.cpp
+++ b/src/libcamera/media_device.cpp
@@ -385,6 +385,35 @@ MediaLink *MediaDevice::link(const MediaPad *source, const MediaPad *sink)
 	return nullptr;
 }

+/**
+ * \brief Reset all links in the media device
+ *
+ * Reset the media device links, clearing the MEDIA_LNK_FL_ENABLED flag
+ * on links which are not flagged as IMMUTABLE.
+ *
+ * \return 0 for success, or a negative error code otherwise
+ */
+int MediaDevice::resetLinks()
+{
+	for (MediaEntity *entity : entities_) {
+		for (MediaPad *pad : entity->pads()) {
+			if (pad->flags() & MEDIA_PAD_FL_SINK)
+				continue;
+
+			for (MediaLink *link : pad->links()) {
+				if (link->flags() & MEDIA_LNK_FL_IMMUTABLE)
+					continue;
+
+				int ret = link->setEnable(false);
+				if (ret)
+					return ret;
+			}
+		}
+	}
+
+	return 0;
+}
+
 /**
  * \var MediaDevice::objects_
  * \brief Global map of media objects (entities, pads, links) keyed by their
@@ -601,4 +630,50 @@ bool MediaDevice::populateLinks(const struct media_v2_topology &topology)
 	return true;
 }

+/**
+ * \brief Apply \a flags to a link between two pads
+ * \param link The link to apply flags on
+ * \param flags The flags to apply to the link
+ *
+ * This function applies the link \a flags (as defined by the MEDIA_LNK_FL_*
+ * macros from the Media Controller API) to the given \a link. It implements
+ * low-level link setup as it performs no checks on the validity of the \a
+ * flags, and assumes that the supplied \a flags are valid for the link (e.g.
+ * immutable links cannot be disabled)."
+*
+ * \sa MediaLink::setEnable(bool enable)
+ *
+ * \return 0 for success, or a negative error code otherwise
+ */
+int MediaDevice::setupLink(const MediaLink *link, unsigned int flags)
+{
+	struct media_link_desc linkDesc = { };
+	MediaPad *source = link->source();
+	MediaPad *sink = link->sink();
+
+	linkDesc.source.entity = source->entity()->id();
+	linkDesc.source.index = source->index();
+	linkDesc.source.flags = MEDIA_PAD_FL_SOURCE;
+
+	linkDesc.sink.entity = sink->entity()->id();
+	linkDesc.sink.index = sink->index();
+	linkDesc.sink.flags = MEDIA_PAD_FL_SINK;
+
+	linkDesc.flags = flags;
+
+	int ret = ioctl(fd_, MEDIA_IOC_SETUP_LINK, &linkDesc);
+	if (ret) {
+		ret = -errno;
+		LOG(Error) << "Failed to setup link: " << strerror(-ret);
+		return ret;
+	}
+
+	LOG(Debug) << source->entity()->name() << "["
+		   << source->index() << "] -> "
+		   << sink->entity()->name() << "["
+		   << sink->index() << "]: " << flags;
+
+	return 0;
+}
+
 } /* namespace libcamera */
diff --git a/src/libcamera/media_object.cpp b/src/libcamera/media_object.cpp
index 612550d..c6cb02b 100644
--- a/src/libcamera/media_object.cpp
+++ b/src/libcamera/media_object.cpp
@@ -15,6 +15,7 @@
 #include <linux/media.h>

 #include "log.h"
+#include "media_device.h"
 #include "media_object.h"

 /**
@@ -89,6 +90,34 @@ namespace libcamera {
  * Each link is referenced in the link array of both of the pads it connect.
  */

+/**
+ * \brief Enable or disable a lik
+ * \param enable True to enable the link, false to disable it
+ *
+ * Set the status of a link, according to the value of \a enable.
+ * Links between two pads can be set to the enabled or disabled state freely,
+ * unless they're immutable links, whose status cannot be changed.
+ * Enabling an immutable link is not considered an error, while trying to
+ * disable it is.
+ *
+ * Enabling a link establishes a data connection between two pads, while
+ * disabling it interrupts such a connections.
+ *
+ * \return 0 on success, or a negative error code otherwise
+ */
+int MediaLink::setEnable(bool enable)
+{
+	unsigned int flags = enable ? MEDIA_LNK_FL_ENABLED : 0;
+
+	int ret = dev_->setupLink(this, flags);
+	if (ret)
+		return ret;
+
+	flags_ = flags;
+
+	return 0;
+}
+
 /**
  * \brief Construct a MediaLink
  * \param link The media link kernel data
--
2.20.1