From 176fb0d108f7495ccf9aa127e1342a1a0d87e004 Mon Sep 17 00:00:00 2001 From: Laurent Pinchart Date: Wed, 9 Dec 2009 08:39:58 -0300 Subject: [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 Acked-by: Hans Verkuil Signed-off-by: Mauro Carvalho Chehab --- Documentation/ABI/testing/sysfs-bus-media | 6 +++ Documentation/DocBook/media-entities.tmpl | 2 + Documentation/DocBook/media.tmpl | 3 ++ Documentation/DocBook/v4l/media-controller.xml | 56 +++++++++++++++++++++ Documentation/media-framework.txt | 67 ++++++++++++++++++++++++++ 5 files changed, 134 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-bus-media create mode 100644 Documentation/DocBook/v4l/media-controller.xml create mode 100644 Documentation/media-framework.txt (limited to 'Documentation') 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 + 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 @@ + + 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; + +&sub-media-controller; + &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 @@ + + + + Laurent + Pinchart +
laurent.pinchart@ideasonboard.com
 + Initial version. + + + + 2010 + Laurent Pinchart + + + + + + 1.0.0 + 2010-11-10 + lp + Initial revision + + + + +Media Controller API + + + Media Controller + +
+ Introduction + 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. + 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. + 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. + 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. + The media controller API aims at solving those problems. +
+ 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. -- cgit v1.2.3-70-g09d2