Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 126 insertions, 0 deletions

diff --git a/Documentation/userspace-api/media/dvb/dvbproperty.rst b/Documentation/userspace-api/media/dvb/dvbproperty.rst
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+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+
+.. _frontend-properties:
+
+**************
+Property types
+**************
+
+Tuning into a Digital TV physical channel and starting decoding it
+requires changing a set of parameters, in order to control the tuner,
+the demodulator, the Linear Low-noise Amplifier (LNA) and to set the
+antenna subsystem via Satellite Equipment Control - SEC (on satellite
+systems). The actual parameters are specific to each particular digital
+TV standards, and may change as the digital TV specs evolves.
+
+In the past (up to DVB API version 3 - DVBv3), the strategy used was to have a
+union with the parameters needed to tune for DVB-S, DVB-C, DVB-T and
+ATSC delivery systems grouped there. The problem is that, as the second
+generation standards appeared, the size of such union was not big
+enough to group the structs that would be required for those new
+standards. Also, extending it would break userspace.
+
+So, the legacy union/struct based approach was deprecated, in favor
+of a properties set approach. On such approach,
+:ref:`FE_GET_PROPERTY and FE_SET_PROPERTY <FE_GET_PROPERTY>` are used
+to setup the frontend and read its status.
+
+The actual action is determined by a set of dtv_property cmd/data pairs.
+With one single ioctl, is possible to get/set up to 64 properties.
+
+This section describes the new and recommended way to set the frontend,
+with supports all digital TV delivery systems.
+
+.. note::
+
+   1. On Linux DVB API version 3, setting a frontend was done via
+      struct :c:type:`dvb_frontend_parameters`.
+
+   2. Don't use DVB API version 3 calls on hardware with supports
+      newer standards. Such API provides no support or a very limited
+      support to new standards and/or new hardware.
+
+   3. Nowadays, most frontends support multiple delivery systems.
+      Only with DVB API version 5 calls it is possible to switch between
+      the multiple delivery systems supported by a frontend.
+
+   4. DVB API version 5 is also called *S2API*, as the first
+      new standard added to it was DVB-S2.
+
+**Example**: in order to set the hardware to tune into a DVB-C channel
+at 651 kHz, modulated with 256-QAM, FEC 3/4 and symbol rate of 5.217
+Mbauds, those properties should be sent to
+:ref:`FE_SET_PROPERTY <FE_GET_PROPERTY>` ioctl:
+
+  :ref:`DTV_DELIVERY_SYSTEM <DTV-DELIVERY-SYSTEM>` = SYS_DVBC_ANNEX_A
+
+  :ref:`DTV_FREQUENCY <DTV-FREQUENCY>` = 651000000
+
+  :ref:`DTV_MODULATION <DTV-MODULATION>` = QAM_256
+
+  :ref:`DTV_INVERSION <DTV-INVERSION>` = INVERSION_AUTO
+
+  :ref:`DTV_SYMBOL_RATE <DTV-SYMBOL-RATE>` = 5217000
+
+  :ref:`DTV_INNER_FEC <DTV-INNER-FEC>` = FEC_3_4
+
+  :ref:`DTV_TUNE <DTV-TUNE>`
+
+The code that would that would do the above is show in
+:ref:`dtv-prop-example`.
+
+.. code-block:: c
+    :caption: Example: Setting digital TV frontend properties
+    :name: dtv-prop-example
+
+    #include <stdio.h>
+    #include <fcntl.h>
+    #include <sys/ioctl.h>
+    #include <linux/dvb/frontend.h>
+
+    static struct dtv_property props[] = {
+	{ .cmd = DTV_DELIVERY_SYSTEM, .u.data = SYS_DVBC_ANNEX_A },
+	{ .cmd = DTV_FREQUENCY,       .u.data = 651000000 },
+	{ .cmd = DTV_MODULATION,      .u.data = QAM_256 },
+	{ .cmd = DTV_INVERSION,       .u.data = INVERSION_AUTO },
+	{ .cmd = DTV_SYMBOL_RATE,     .u.data = 5217000 },
+	{ .cmd = DTV_INNER_FEC,       .u.data = FEC_3_4 },
+	{ .cmd = DTV_TUNE }
+    };
+
+    static struct dtv_properties dtv_prop = {
+	.num = 6, .props = props
+    };
+
+    int main(void)
+    {
+	int fd = open("/dev/dvb/adapter0/frontend0", O_RDWR);
+
+	if (!fd) {
+	    perror ("open");
+	    return -1;
+	}
+	if (ioctl(fd, FE_SET_PROPERTY, &dtv_prop) == -1) {
+	    perror("ioctl");
+	    return -1;
+	}
+	printf("Frontend set\\n");
+	return 0;
+    }
+
+.. attention:: While it is possible to directly call the Kernel code like the
+   above example, it is strongly recommended to use
+   `libdvbv5 <https://linuxtv.org/docs/libdvbv5/index.html>`__, as it
+   provides abstraction to work with the supported digital TV standards and
+   provides methods for usual operations like program scanning and to
+   read/write channel descriptor files.
+
+.. toctree::
+    :maxdepth: 1
+
+    fe_property_parameters
+    frontend-stat-properties
+    frontend-property-terrestrial-systems
+    frontend-property-cable-systems
+    frontend-property-satellite-systems
+    frontend-header