From 2c3c1048746a4622d8c89a29670120dc8fab93c4 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 20:49:45 +0200 Subject: Adding upstream version 6.1.76. Signed-off-by: Daniel Baumann --- .../userspace-api/media/v4l/dev-radio.rst | 52 ++++++++++++++++++++++ 1 file changed, 52 insertions(+) create mode 100644 Documentation/userspace-api/media/v4l/dev-radio.rst (limited to 'Documentation/userspace-api/media/v4l/dev-radio.rst') 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 `, and must support +the :ref:`tuner or modulator ` 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 ` or +:ref:`VIDIOC_G_MODULATOR ` ioctl reports the +supported frequency range. -- cgit v1.2.3