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author | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2016-07-08 11:40:06 -0300 |
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committer | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2016-07-08 11:59:40 -0300 |
commit | 60c2820d0f6d3497975b6488e2599f8f611d8b95 (patch) | |
tree | b3b03707c6438ea9b99cc57e847ebf517f968ab1 /Documentation/media/uapi/mediactl/media-controller-intro.rst | |
parent | a97369b5e21ea9b8b5fef7c0f4f48bbe60c07ca3 (diff) | |
download | op-kernel-dev-60c2820d0f6d3497975b6488e2599f8f611d8b95.zip op-kernel-dev-60c2820d0f6d3497975b6488e2599f8f611d8b95.tar.gz |
doc_rst: rename the media Sphinx suff to Documentation/media
The name of the subsystem is "media", and not "linux_tv". Also,
as we plan to add other stuff there in the future, let's
rename also the media uAPI book to media_uapi, to make it
clearer.
No functional changes.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Diffstat (limited to 'Documentation/media/uapi/mediactl/media-controller-intro.rst')
-rw-r--r-- | Documentation/media/uapi/mediactl/media-controller-intro.rst | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/Documentation/media/uapi/mediactl/media-controller-intro.rst b/Documentation/media/uapi/mediactl/media-controller-intro.rst new file mode 100644 index 0000000..3e776c0 --- /dev/null +++ b/Documentation/media/uapi/mediactl/media-controller-intro.rst @@ -0,0 +1,33 @@ +.. -*- coding: utf-8; mode: rst -*- + +.. _media-controller-intro: + +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. |