doc-rst: linux_tv DocBook to reST migration (docs-next)

This is the restructuredText (reST) migration of the ``media``
DocBook-XML set from the linux_tv project.

Signed-off-by: Markus Heiser <markus.heiser@darmarIT.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

1 files changed, 91 insertions, 0 deletions

diff --git a/Documentation/linux_tv/media/v4l/tuner.rst b/Documentation/linux_tv/media/v4l/tuner.rst
new file mode 100644
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+.. -*- coding: utf-8; mode: rst -*-
+
+.. _tuner:
+
+*********************
+Tuners and Modulators
+*********************
+
+
+Tuners
+======
+
+Video input devices can have one or more tuners demodulating a RF
+signal. Each tuner is associated with one or more video inputs,
+depending on the number of RF connectors on the tuner. The ``type``
+field of the respective struct :ref:`v4l2_input <v4l2-input>`
+returned by the :ref:`VIDIOC_ENUMINPUT <vidioc-enuminput>` ioctl is
+set to ``V4L2_INPUT_TYPE_TUNER`` and its ``tuner`` field contains the
+index number of the tuner.
+
+Radio input devices have exactly one tuner with index zero, no video
+inputs.
+
+To query and change tuner properties applications use the
+:ref:`VIDIOC_G_TUNER <vidioc-g-tuner>` and
+:ref:`VIDIOC_S_TUNER <vidioc-g-tuner>` ioctls, respectively. The
+struct :ref:`v4l2_tuner <v4l2-tuner>` returned by ``VIDIOC_G_TUNER``
+also contains signal status information applicable when the tuner of the
+current video or radio input is queried. Note that ``VIDIOC_S_TUNER``
+does not switch the current tuner, when there is more than one at all.
+The tuner is solely determined by the current video input. Drivers must
+support both ioctls and set the ``V4L2_CAP_TUNER`` flag in the struct
+:ref:`v4l2_capability <v4l2-capability>` returned by the
+:ref:`VIDIOC_QUERYCAP <vidioc-querycap>` ioctl when the device has
+one or more tuners.
+
+
+Modulators
+==========
+
+Video output devices can have one or more modulators, uh, modulating a
+video signal for radiation or connection to the antenna input of a TV
+set or video recorder. Each modulator is associated with one or more
+video outputs, depending on the number of RF connectors on the
+modulator. The ``type`` field of the respective struct
+:ref:`v4l2_output <v4l2-output>` returned by the
+:ref:`VIDIOC_ENUMOUTPUT <vidioc-enumoutput>` ioctl is set to
+``V4L2_OUTPUT_TYPE_MODULATOR`` and its ``modulator`` field contains the
+index number of the modulator.
+
+Radio output devices have exactly one modulator with index zero, no
+video outputs.
+
+A video or radio device cannot support both a tuner and a modulator. Two
+separate device nodes will have to be used for such hardware, one that
+supports the tuner functionality and one that supports the modulator
+functionality. The reason is a limitation with the
+:ref:`VIDIOC_S_FREQUENCY <vidioc-g-frequency>` ioctl where you
+cannot specify whether the frequency is for a tuner or a modulator.
+
+To query and change modulator properties applications use the
+:ref:`VIDIOC_G_MODULATOR <vidioc-g-modulator>` and
+:ref:`VIDIOC_S_MODULATOR <vidioc-g-modulator>` ioctl. Note that
+``VIDIOC_S_MODULATOR`` does not switch the current modulator, when there
+is more than one at all. The modulator is solely determined by the
+current video output. Drivers must support both ioctls and set the
+``V4L2_CAP_MODULATOR`` flag in the struct
+:ref:`v4l2_capability <v4l2-capability>` returned by the
+:ref:`VIDIOC_QUERYCAP <vidioc-querycap>` ioctl when the device has
+one or more modulators.
+
+
+Radio Frequency
+===============
+
+To get and set the tuner or modulator radio frequency applications use
+the :ref:`VIDIOC_G_FREQUENCY <vidioc-g-frequency>` and
+:ref:`VIDIOC_S_FREQUENCY <vidioc-g-frequency>` ioctl which both take
+a pointer to a struct :ref:`v4l2_frequency <v4l2-frequency>`. These
+ioctls are used for TV and radio devices alike. Drivers must support
+both ioctls when the tuner or modulator ioctls are supported, or when
+the device is a radio device.
+
+
+.. ------------------------------------------------------------------------------
+.. This file was automatically converted from DocBook-XML with the dbxml
+.. library (https://github.com/return42/sphkerneldoc). The origin XML comes
+.. from the linux kernel, refer to:
+..
+.. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook
+.. ------------------------------------------------------------------------------