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authorLaurent Pinchart <laurent.pinchart@ideasonboard.com>2009-12-09 08:39:58 -0300
committerMauro Carvalho Chehab <mchehab@redhat.com>2011-03-22 04:53:09 -0300
commit176fb0d108f7495ccf9aa127e1342a1a0d87e004 (patch)
treea1b54ad186dde663853d4d2d24f42cd7c0f94bfb /Documentation
parentcf4b9211b5680cd9ca004232e517fb7ec5bf5316 (diff)
[media] media: Media device
The media_device structure abstracts functions common to all kind of media devices (v4l2, dvb, alsa, ...). It manages media entities and offers a userspace API to discover and configure the media device internal topology. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Acked-by: Hans Verkuil <hverkuil@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/ABI/testing/sysfs-bus-media6
-rw-r--r--Documentation/DocBook/media-entities.tmpl2
-rw-r--r--Documentation/DocBook/media.tmpl3
-rw-r--r--Documentation/DocBook/v4l/media-controller.xml56
-rw-r--r--Documentation/media-framework.txt67
5 files changed, 134 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-media b/Documentation/ABI/testing/sysfs-bus-media
new file mode 100644
index 00000000000..7057e574154
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-media
@@ -0,0 +1,6 @@
+What: /sys/bus/media/devices/.../model
+Date: January 2011
+Contact: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
+ linux-media@vger.kernel.org
+Description: Contains the device model name in UTF-8. The device version is
+ is not be appended to the model name.
diff --git a/Documentation/DocBook/media-entities.tmpl b/Documentation/DocBook/media-entities.tmpl
index d2f99e5a3a2..c47897f046b 100644
--- a/Documentation/DocBook/media-entities.tmpl
+++ b/Documentation/DocBook/media-entities.tmpl
@@ -327,6 +327,8 @@
<!ENTITY sub-media-entities SYSTEM "media-entities.tmpl">
<!ENTITY sub-media-indices SYSTEM "media-indices.tmpl">
+<!ENTITY sub-media-controller SYSTEM "v4l/media-controller.xml">
+
<!-- Function Reference -->
<!ENTITY close SYSTEM "v4l/func-close.xml">
<!ENTITY ioctl SYSTEM "v4l/func-ioctl.xml">
diff --git a/Documentation/DocBook/media.tmpl b/Documentation/DocBook/media.tmpl
index a99088aae1a..88f2cc680cc 100644
--- a/Documentation/DocBook/media.tmpl
+++ b/Documentation/DocBook/media.tmpl
@@ -106,6 +106,9 @@ Foundation. A copy of the license is included in the chapter entitled
&sub-remote_controllers;
</chapter>
</part>
+<part id="media_common">
+&sub-media-controller;
+</part>
&sub-fdl-appendix;
diff --git a/Documentation/DocBook/v4l/media-controller.xml b/Documentation/DocBook/v4l/media-controller.xml
new file mode 100644
index 00000000000..253ddb4426c
--- /dev/null
+++ b/Documentation/DocBook/v4l/media-controller.xml
@@ -0,0 +1,56 @@
+<partinfo>
+ <authorgroup>
+ <author>
+ <firstname>Laurent</firstname>
+ <surname>Pinchart</surname>
+ <affiliation><address><email>laurent.pinchart@ideasonboard.com</email></address></affiliation>
+ <contrib>Initial version.</contrib>
+ </author>
+ </authorgroup>
+ <copyright>
+ <year>2010</year>
+ <holder>Laurent Pinchart</holder>
+ </copyright>
+
+ <revhistory>
+ <!-- Put document revisions here, newest first. -->
+ <revision>
+ <revnumber>1.0.0</revnumber>
+ <date>2010-11-10</date>
+ <authorinitials>lp</authorinitials>
+ <revremark>Initial revision</revremark>
+ </revision>
+ </revhistory>
+</partinfo>
+
+<title>Media Controller API</title>
+
+<chapter id="media_controller">
+ <title>Media Controller</title>
+
+ <section id="media-controller-intro">
+ <title>Introduction</title>
+ <para>Media devices increasingly handle multiple related functions. Many USB
+ cameras include microphones, video capture hardware can also output video,
+ or SoC camera interfaces also perform memory-to-memory operations similar to
+ video codecs.</para>
+ <para>Independent functions, even when implemented in the same hardware, can
+ be modelled as separate devices. A USB camera with a microphone will be
+ presented to userspace applications as V4L2 and ALSA capture devices. The
+ devices' relationships (when using a webcam, end-users shouldn't have to
+ manually select the associated USB microphone), while not made available
+ directly to applications by the drivers, can usually be retrieved from
+ sysfs.</para>
+ <para>With more and more advanced SoC devices being introduced, the current
+ approach will not scale. Device topologies are getting increasingly complex
+ and can't always be represented by a tree structure. Hardware blocks are
+ shared between different functions, creating dependencies between seemingly
+ unrelated devices.</para>
+ <para>Kernel abstraction APIs such as V4L2 and ALSA provide means for
+ applications to access hardware parameters. As newer hardware expose an
+ increasingly high number of those parameters, drivers need to guess what
+ applications really require based on limited information, thereby
+ implementing policies that belong to userspace.</para>
+ <para>The media controller API aims at solving those problems.</para>
+ </section>
+</chapter>
diff --git a/Documentation/media-framework.txt b/Documentation/media-framework.txt
new file mode 100644
index 00000000000..1844c3f1072
--- /dev/null
+++ b/Documentation/media-framework.txt
@@ -0,0 +1,67 @@
+Linux kernel media framework
+============================
+
+This document describes the Linux kernel media framework, its data structures,
+functions and their usage.
+
+
+Introduction
+------------
+
+The media controller API is documented in DocBook format in
+Documentation/DocBook/v4l/media-controller.xml. This document will focus on
+the kernel-side implementation of the media framework.
+
+
+Media device
+------------
+
+A media device is represented by a struct media_device instance, defined in
+include/media/media-device.h. Allocation of the structure is handled by the
+media device driver, usually by embedding the media_device instance in a
+larger driver-specific structure.
+
+Drivers register media device instances by calling
+
+ media_device_register(struct media_device *mdev);
+
+The caller is responsible for initializing the media_device structure before
+registration. The following fields must be set:
+
+ - dev must point to the parent device (usually a pci_dev, usb_interface or
+ platform_device instance).
+
+ - model must be filled with the device model name as a NUL-terminated UTF-8
+ string. The device/model revision must not be stored in this field.
+
+The following fields are optional:
+
+ - serial is a unique serial number stored as a NUL-terminated ASCII string.
+ The field is big enough to store a GUID in text form. If the hardware
+ doesn't provide a unique serial number this field must be left empty.
+
+ - bus_info represents the location of the device in the system as a
+ NUL-terminated ASCII string. For PCI/PCIe devices bus_info must be set to
+ "PCI:" (or "PCIe:") followed by the value of pci_name(). For USB devices,
+ the usb_make_path() function must be used. This field is used by
+ applications to distinguish between otherwise identical devices that don't
+ provide a serial number.
+
+ - hw_revision is the hardware device revision in a driver-specific format.
+ When possible the revision should be formatted with the KERNEL_VERSION
+ macro.
+
+ - driver_version is formatted with the KERNEL_VERSION macro. The version
+ minor must be incremented when new features are added to the userspace API
+ without breaking binary compatibility. The version major must be
+ incremented when binary compatibility is broken.
+
+Upon successful registration a character device named media[0-9]+ is created.
+The device major and minor numbers are dynamic. The model name is exported as
+a sysfs attribute.
+
+Drivers unregister media device instances by calling
+
+ media_device_unregister(struct media_device *mdev);
+
+Unregistering a media device that hasn't been registered is *NOT* safe.