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Subject[RFC/PATCH v7 08/12] media: Links setup
Date
Create the following ioctl and implement it at the media device level to
setup links.

- MEDIA_IOC_SETUP_LINK: Modify the properties of a given link

The only property that can currently be modified is the ENABLED link
flag to enable/disable a link. Links marked with the IMMUTABLE link flag
can not be enabled or disabled.

Enabling or disabling a link has effects on entities' use count. Those
changes are automatically propagated through the graph.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Stanimir Varbanov <svarbanov@mm-sol.com>
Signed-off-by: Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>
---
Documentation/DocBook/media-entities.tmpl | 2 +
Documentation/DocBook/v4l/media-controller.xml | 1 +
Documentation/DocBook/v4l/media-ioc-setup-link.xml | 90 +++++++++
Documentation/media-framework.txt | 47 +++++
drivers/media/media-device.c | 45 +++++
drivers/media/media-entity.c | 208 ++++++++++++++++++++
include/linux/media.h | 1 +
include/media/media-entity.h | 8 +
8 files changed, 402 insertions(+), 0 deletions(-)
create mode 100644 Documentation/DocBook/v4l/media-ioc-setup-link.xml
diff --git a/Documentation/DocBook/media-entities.tmpl b/Documentation/DocBook/media-entities.tmpl
index 6e7dae4..679c585 100644
--- a/Documentation/DocBook/media-entities.tmpl
+++ b/Documentation/DocBook/media-entities.tmpl
@@ -94,6 +94,7 @@
<!ENTITY MEDIA-IOC-DEVICE-INFO "<link linkend='media-ioc-device-info'><constant>MEDIA_IOC_DEVICE_INFO</constant></link>">
<!ENTITY MEDIA-IOC-ENUM-ENTITIES "<link linkend='media-ioc-enum-entities'><constant>MEDIA_IOC_ENUM_ENTITIES</constant></link>">
<!ENTITY MEDIA-IOC-ENUM-LINKS "<link linkend='media-ioc-enum-links'><constant>MEDIA_IOC_ENUM_LINKS</constant></link>">
+<!ENTITY MEDIA-IOC-SETUP-LINK "<link linkend='media-ioc-setup-link'><constant>MEDIA_IOC_SETUP_LINK</constant></link>">

<!-- Types -->
<!ENTITY v4l2-std-id "<link linkend='v4l2-std-id'>v4l2_std_id</link>">
@@ -342,6 +343,7 @@
<!ENTITY sub-media-ioc-device-info SYSTEM "v4l/media-ioc-device-info.xml">
<!ENTITY sub-media-ioc-enum-entities SYSTEM "v4l/media-ioc-enum-entities.xml">
<!ENTITY sub-media-ioc-enum-links SYSTEM "v4l/media-ioc-enum-links.xml">
+<!ENTITY sub-media-ioc-setup-link SYSTEM "v4l/media-ioc-setup-link.xml">

<!-- Function Reference -->
<!ENTITY close SYSTEM "v4l/func-close.xml">
diff --git a/Documentation/DocBook/v4l/media-controller.xml b/Documentation/DocBook/v4l/media-controller.xml
index 2c4fd2b..2dc25e1 100644
--- a/Documentation/DocBook/v4l/media-controller.xml
+++ b/Documentation/DocBook/v4l/media-controller.xml
@@ -85,4 +85,5 @@
&sub-media-ioc-device-info;
&sub-media-ioc-enum-entities;
&sub-media-ioc-enum-links;
+ &sub-media-ioc-setup-link;
</appendix>
diff --git a/Documentation/DocBook/v4l/media-ioc-setup-link.xml b/Documentation/DocBook/v4l/media-ioc-setup-link.xml
new file mode 100644
index 0000000..09ab3d2
--- /dev/null
+++ b/Documentation/DocBook/v4l/media-ioc-setup-link.xml
@@ -0,0 +1,90 @@
+<refentry id="media-ioc-setup-link">
+ <refmeta>
+ <refentrytitle>ioctl MEDIA_IOC_SETUP_LINK</refentrytitle>
+ &manvol;
+ </refmeta>
+
+ <refnamediv>
+ <refname>MEDIA_IOC_SETUP_LINK</refname>
+ <refpurpose>Modify the properties of a link</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcprototype>
+ <funcdef>int <function>ioctl</function></funcdef>
+ <paramdef>int <parameter>fd</parameter></paramdef>
+ <paramdef>int <parameter>request</parameter></paramdef>
+ <paramdef>struct media_link_desc *<parameter>argp</parameter></paramdef>
+ </funcprototype>
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Arguments</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><parameter>fd</parameter></term>
+ <listitem>
+ <para>File descriptor returned by
+ <link linkend='media-func-open'><function>open()</function></link>.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><parameter>request</parameter></term>
+ <listitem>
+ <para>MEDIA_IOC_ENUM_LINKS</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><parameter>argp</parameter></term>
+ <listitem>
+ <para></para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para>To change link properties applications fill a &media-link-desc; with
+ link identification information (source and sink pad) and the new requested
+ link flags. They then call the MEDIA_IOC_SETUP_LINK ioctl with a pointer to
+ that structure.</para>
+ <para>The only configurable property is the <constant>ENABLED</constant>
+ link flag to enable/disable a link. Links marked with the
+ <constant>IMMUTABLE</constant> link flag can not be enabled or disabled.
+ </para>
+ <para>Link configuration has no side effect on other links. If an enabled
+ link at the sink pad prevents the link from being enabled, the driver
+ returns with an &EBUSY;.</para>
+ <para>If the specified link can't be found the driver returns with an
+ &EINVAL;.</para>
+ </refsect1>
+
+ <refsect1>
+ &return-value;
+
+ <variablelist>
+ <varlistentry>
+ <term><errorcode>EBUSY</errorcode></term>
+ <listitem>
+ <para>The link properties can't be changed because the link is
+ currently busy. This can be caused, for instance, by an active media
+ stream (audio or video) on the link. The ioctl shouldn't be retried if
+ no other action is performed before to fix the problem.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><errorcode>EINVAL</errorcode></term>
+ <listitem>
+ <para>The &media-link-desc; references a non-existing link, or the
+ link is immutable and an attempt to modify its configuration was made.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+</refentry>
diff --git a/Documentation/media-framework.txt b/Documentation/media-framework.txt
index e90969e..4603417 100644
--- a/Documentation/media-framework.txt
+++ b/Documentation/media-framework.txt
@@ -259,6 +259,16 @@ When the graph traversal is complete the function will return NULL.
Graph traversal can be interrupted at any moment. No cleanup function call is
required and the graph structure can be freed normally.

+Helper functions can be used to find a link between two given pads, or a pad
+connected to another pad through an enabled link
+
+ media_entity_find_link(struct media_pad *source,
+ struct media_pad *sink);
+
+ media_entity_remote_source(struct media_pad *pad);
+
+Refer to the kerneldoc documentation for more information.
+

Reference counting and power handling
-------------------------------------
@@ -296,3 +306,40 @@ required, drivers don't need to provide a set_power operation. The operation
is allowed to fail when turning power on, in which case the media_entity_get
function will return NULL.

+
+Links setup
+-----------
+
+Link properties can be modified at runtime by calling
+
+ media_entity_setup_link(struct media_link *link, u32 flags);
+
+The flags argument contains the requested new link flags.
+
+The only configurable property is the ENABLED link flag to enable/disable a
+link. Links marked with the IMMUTABLE link flag can not be enabled or disabled.
+
+When a link is enabled or disabled, the media framework calls the
+link_setup operation for the two entities at the source and sink of the link,
+in that order. If the second link_setup call fails, another link_setup call is
+made on the first entity to restore the original link flags.
+
+Entity drivers must implement the link_setup operation if any of their links
+is non-immutable. The operation must either configure the hardware or store
+the configuration information to be applied later.
+
+Link configuration must not have any side effect on other links. If an enabled
+link at a sink pad prevents another link at the same pad from being disabled,
+the link_setup operation must return -EBUSY and can't implicitly disable the
+first enabled link.
+
+Enabling and disabling a link has effects on entities' reference counts. When
+two sub-graphs are connected, the reference count of each of them is incremented
+by the total reference count of all node entities in the other sub-graph. When
+two sub-graphs are disconnected, the reverse operation is performed. In both
+cases the set_power operations are called accordingly, ensuring that the
+link_setup calls are made with power active on the source and sink entities.
+
+In other words, enabling or disabling a link propagates reference count changes
+through the graph, and the final state is identical to what it would have been
+if the link had been enabled or disabled from the start.
diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
index f41febc..2396a77 100644
--- a/drivers/media/media-device.c
+++ b/drivers/media/media-device.c
@@ -172,6 +172,44 @@ static long media_device_enum_links(struct media_device *mdev,
return 0;
}

+static long media_device_setup_link(struct media_device *mdev,
+ struct media_link_desc __user *_ulink)
+{
+ struct media_link *link = NULL;
+ struct media_link_desc ulink;
+ struct media_entity *source;
+ struct media_entity *sink;
+ int ret;
+
+ if (copy_from_user(&ulink, _ulink, sizeof(ulink)))
+ return -EFAULT;
+
+ /* Find the source and sink entities and link.
+ */
+ source = find_entity(mdev, ulink.source.entity);
+ sink = find_entity(mdev, ulink.sink.entity);
+
+ if (source == NULL || sink == NULL)
+ return -EINVAL;
+
+ if (ulink.source.index >= source->num_pads ||
+ ulink.sink.index >= sink->num_pads)
+ return -EINVAL;
+
+ link = media_entity_find_link(&source->pads[ulink.source.index],
+ &sink->pads[ulink.sink.index]);
+ if (link == NULL)
+ return -EINVAL;
+
+ /* Setup the link on both entities. */
+ ret = __media_entity_setup_link(link, ulink.flags);
+
+ if (copy_to_user(_ulink, &ulink, sizeof(ulink)))
+ return -EFAULT;
+
+ return ret;
+}
+
static long media_device_ioctl(struct file *filp, unsigned int cmd,
unsigned long arg)
{
@@ -197,6 +235,13 @@ static long media_device_ioctl(struct file *filp, unsigned int cmd,
mutex_unlock(&dev->graph_mutex);
break;

+ case MEDIA_IOC_SETUP_LINK:
+ mutex_lock(&dev->graph_mutex);
+ ret = media_device_setup_link(dev,
+ (struct media_link_desc __user *)arg);
+ mutex_unlock(&dev->graph_mutex);
+ break;
+
default:
ret = -ENOIOCTLCMD;
}
diff --git a/drivers/media/media-entity.c b/drivers/media/media-entity.c
index c541f4a..53718f1 100644
--- a/drivers/media/media-entity.c
+++ b/drivers/media/media-entity.c
@@ -200,6 +200,25 @@ EXPORT_SYMBOL_GPL(media_entity_graph_walk_next);
* Power state handling
*/

+/*
+ * Return power count of nodes directly or indirectly connected to
+ * a given entity.
+ */
+static int media_entity_count_node(struct media_entity *entity)
+{
+ struct media_entity_graph graph;
+ int use = 0;
+
+ media_entity_graph_walk_start(&graph, entity);
+
+ while ((entity = media_entity_graph_walk_next(&graph))) {
+ if (media_entity_type(entity) == MEDIA_ENTITY_TYPE_DEVNODE)
+ use += entity->use_count;
+ }
+
+ return use;
+}
+
/* Apply use count to an entity. */
static void media_entity_use_apply_one(struct media_entity *entity, int change)
{
@@ -263,6 +282,32 @@ static int media_entity_power_apply(struct media_entity *entity, int change)
return ret;
}

+/* Apply the power state changes when connecting two entities. */
+static int media_entity_power_connect(struct media_entity *one,
+ struct media_entity *theother)
+{
+ int power_one = media_entity_count_node(one);
+ int power_theother = media_entity_count_node(theother);
+ int ret = 0;
+
+ ret = media_entity_power_apply(one, power_theother);
+ if (ret < 0)
+ return ret;
+
+ return media_entity_power_apply(theother, power_one);
+}
+
+static void media_entity_power_disconnect(struct media_entity *one,
+ struct media_entity *theother)
+{
+ int power_one = media_entity_count_node(one);
+ int power_theother = media_entity_count_node(theother);
+
+ /* Powering off entities is assumed to never fail. */
+ media_entity_power_apply(one, -power_theother);
+ media_entity_power_apply(theother, -power_one);
+}
+
/*
* Apply use count change to graph and change power state of entities
* accordingly.
@@ -406,3 +451,166 @@ media_entity_create_link(struct media_entity *source, u16 source_pad,
return 0;
}
EXPORT_SYMBOL_GPL(media_entity_create_link);
+
+static int __media_entity_setup_link_notify(struct media_link *link, u32 flags)
+{
+ const u32 mask = MEDIA_LINK_FLAG_ENABLED;
+ int ret;
+
+ /* Notify both entities. */
+ ret = media_entity_call(link->source->entity, link_setup,
+ link->source, link->sink, flags);
+ if (ret < 0 && ret != -ENOIOCTLCMD)
+ return ret;
+
+ ret = media_entity_call(link->sink->entity, link_setup,
+ link->sink, link->source, flags);
+ if (ret < 0 && ret != -ENOIOCTLCMD) {
+ media_entity_call(link->source->entity, link_setup,
+ link->source, link->sink, link->flags);
+ return ret;
+ }
+
+ link->flags = (link->flags & ~mask) | (flags & mask);
+ link->reverse->flags = link->flags;
+
+ return 0;
+}
+
+/**
+ * __media_entity_setup_link - Configure a media link
+ * @link: The link being configured
+ * @flags: Link configuration flags
+ *
+ * The bulk of link setup is handled by the two entities connected through the
+ * link. This function notifies both entities of the link configuration change.
+ *
+ * If the link is immutable or if the current and new configuration are
+ * identical, return immediately.
+ *
+ * The user is expected to hold link->source->parent->mutex. If not,
+ * media_entity_setup_link() should be used instead.
+ */
+int __media_entity_setup_link(struct media_link *link, u32 flags)
+{
+ struct media_entity *source, *sink;
+ int ret = -EBUSY;
+
+ if (link == NULL)
+ return -EINVAL;
+
+ if (link->flags & MEDIA_LINK_FLAG_IMMUTABLE)
+ return link->flags == flags ? 0 : -EINVAL;
+
+ if (link->flags == flags)
+ return 0;
+
+ source = __media_entity_get(link->source->entity);
+ if (!source)
+ return ret;
+
+ sink = __media_entity_get(link->sink->entity);
+ if (!sink)
+ goto err___media_entity_get;
+
+ if (flags & MEDIA_LINK_FLAG_ENABLED) {
+ ret = media_entity_power_connect(source, sink);
+ if (ret < 0)
+ goto err_media_entity_power_connect;
+ }
+
+ ret = __media_entity_setup_link_notify(link, flags);
+ if (ret < 0)
+ goto err___media_entity_setup_link_notify;
+
+ if (!(flags & MEDIA_LINK_FLAG_ENABLED))
+ media_entity_power_disconnect(source, sink);
+
+ __media_entity_put(sink);
+ __media_entity_put(source);
+
+ return 0;
+
+err___media_entity_setup_link_notify:
+ if (flags & MEDIA_LINK_FLAG_ENABLED)
+ media_entity_power_disconnect(source, sink);
+err_media_entity_power_connect:
+ __media_entity_put(sink);
+err___media_entity_get:
+ __media_entity_put(source);
+
+ return ret;
+}
+
+int media_entity_setup_link(struct media_link *link, u32 flags)
+{
+ int ret;
+
+ mutex_lock(&link->source->entity->parent->graph_mutex);
+ ret = __media_entity_setup_link(link, flags);
+ mutex_unlock(&link->source->entity->parent->graph_mutex);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(media_entity_setup_link);
+
+/**
+ * media_entity_find_link - Find a link between two pads
+ * @source: Source pad
+ * @sink: Sink pad
+ *
+ * Return a pointer to the link between the two entities. If no such link
+ * exists, return NULL.
+ */
+struct media_link *
+media_entity_find_link(struct media_pad *source, struct media_pad *sink)
+{
+ struct media_link *link;
+ unsigned int i;
+
+ for (i = 0; i < source->entity->num_links; ++i) {
+ link = &source->entity->links[i];
+
+ if (link->source->entity == source->entity &&
+ link->source->index == source->index &&
+ link->sink->entity == sink->entity &&
+ link->sink->index == sink->index)
+ return link;
+ }
+
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(media_entity_find_link);
+
+/**
+ * media_entity_remote_source - Find the source pad at the remote end of a link
+ * @pad: Sink pad at the local end of the link
+ *
+ * Search for a remote source pad connected to the given sink pad by iterating
+ * over all links originating or terminating at that pad until an enabled link
+ * is found.
+ *
+ * Return a pointer to the pad at the remote end of the first found enabled
+ * link, or NULL if no enabled link has been found.
+ */
+struct media_pad *media_entity_remote_source(struct media_pad *pad)
+{
+ unsigned int i;
+
+ for (i = 0; i < pad->entity->num_links; i++) {
+ struct media_link *link = &pad->entity->links[i];
+
+ if (!(link->flags & MEDIA_LINK_FLAG_ENABLED))
+ continue;
+
+ if (link->source == pad)
+ return link->sink;
+
+ if (link->sink == pad)
+ return link->source;
+ }
+
+ return NULL;
+
+}
+EXPORT_SYMBOL_GPL(media_entity_remote_source);
diff --git a/include/linux/media.h b/include/linux/media.h
index 3b1c065..0611e3d 100644
--- a/include/linux/media.h
+++ b/include/linux/media.h
@@ -126,5 +126,6 @@ struct media_links_enum {
#define MEDIA_IOC_DEVICE_INFO _IOWR('M', 1, struct media_device_info)
#define MEDIA_IOC_ENUM_ENTITIES _IOWR('M', 2, struct media_entity_desc)
#define MEDIA_IOC_ENUM_LINKS _IOWR('M', 3, struct media_links_enum)
+#define MEDIA_IOC_SETUP_LINK _IOWR('M', 4, struct media_link_desc)

#endif /* __LINUX_MEDIA_H */
diff --git a/include/media/media-entity.h b/include/media/media-entity.h
index f45a2a5..36ad6c7 100644
--- a/include/media/media-entity.h
+++ b/include/media/media-entity.h
@@ -40,6 +40,9 @@ struct media_pad {
};

struct media_entity_operations {
+ int (*link_setup)(struct media_entity *entity,
+ const struct media_pad *local,
+ const struct media_pad *remote, u32 flags);
int (*set_power)(struct media_entity *entity, int power);
};

@@ -114,6 +117,11 @@ int media_entity_init(struct media_entity *entity, u16 num_pads,
void media_entity_cleanup(struct media_entity *entity);
int media_entity_create_link(struct media_entity *source, u16 source_pad,
struct media_entity *sink, u16 sink_pad, u32 flags);
+int __media_entity_setup_link(struct media_link *link, u32 flags);
+int media_entity_setup_link(struct media_link *link, u32 flags);
+struct media_link *media_entity_find_link(struct media_pad *source,
+ struct media_pad *sink);
+struct media_pad *media_entity_remote_source(struct media_pad *pad);

struct media_entity *media_entity_get(struct media_entity *entity);
void media_entity_put(struct media_entity *entity);
--
1.7.2.2


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