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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
commit | 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch) | |
tree | a94efe259b9009378be6d90eb30d2b019d95c194 /Documentation/userspace-api/media/v4l/dev-radio.rst | |
parent | Initial commit. (diff) | |
download | linux-upstream/5.10.209.tar.xz linux-upstream/5.10.209.zip |
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | Documentation/userspace-api/media/v4l/dev-radio.rst | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/Documentation/userspace-api/media/v4l/dev-radio.rst b/Documentation/userspace-api/media/v4l/dev-radio.rst new file mode 100644 index 000000000..284ce96a1 --- /dev/null +++ b/Documentation/userspace-api/media/v4l/dev-radio.rst @@ -0,0 +1,52 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later + +.. _radio: + +*************** +Radio Interface +*************** + +This interface is intended for AM and FM (analog) radio receivers and +transmitters. + +Conventionally V4L2 radio devices are accessed through character device +special files named ``/dev/radio`` and ``/dev/radio0`` to +``/dev/radio63`` with major number 81 and minor numbers 64 to 127. + + +Querying Capabilities +===================== + +Devices supporting the radio interface set the ``V4L2_CAP_RADIO`` and +``V4L2_CAP_TUNER`` or ``V4L2_CAP_MODULATOR`` flag in the +``capabilities`` field of struct +:c:type:`v4l2_capability` returned by the +:ref:`VIDIOC_QUERYCAP` ioctl. Other combinations of +capability flags are reserved for future extensions. + + +Supplemental Functions +====================== + +Radio devices can support :ref:`controls <control>`, and must support +the :ref:`tuner or modulator <tuner>` ioctls. + +They do not support the video input or output, audio input or output, +video standard, cropping and scaling, compression and streaming +parameter, or overlay ioctls. All other ioctls and I/O methods are +reserved for future extensions. + + +Programming +=========== + +Radio devices may have a couple audio controls (as discussed in +:ref:`control`) such as a volume control, possibly custom controls. +Further all radio devices have one tuner or modulator (these are +discussed in :ref:`tuner`) with index number zero to select the radio +frequency and to determine if a monaural or FM stereo program is +received/emitted. Drivers switch automatically between AM and FM +depending on the selected frequency. The +:ref:`VIDIOC_G_TUNER <VIDIOC_G_TUNER>` or +:ref:`VIDIOC_G_MODULATOR <VIDIOC_G_MODULATOR>` ioctl reports the +supported frequency range. |