[deliverable/linux.git] / Documentation / media / uapi / dvb / fe-set-voltage.rst

.. -*- coding: utf-8; mode: rst -*-

.. _FE_SET_VOLTAGE:

********************
ioctl FE_SET_VOLTAGE
********************

Name
====

FE_SET_VOLTAGE - Allow setting the DC level sent to the antenna subsystem.


Synopsis
========

.. c:function:: int ioctl( int fd, FE_SET_VOLTAGE, enum fe_sec_voltage *voltage )
    :name: FE_SET_VOLTAGE


Arguments
=========

``fd``
    File descriptor returned by :ref:`open() <frontend_f_open>`.

``voltage``
    pointer to enum :c:type:`fe_sec_voltage`

    Valid values are described at enum
    :c:type:`fe_sec_voltage`.


Description
===========

This ioctl allows to set the DC voltage level sent through the antenna
cable to 13V, 18V or off.

Usually, a satellite antenna subsystems require that the digital TV
device to send a DC voltage to feed power to the LNBf. Depending on the
LNBf type, the polarization or the intermediate frequency (IF) of the
LNBf can controlled by the voltage level. Other devices (for example,
the ones that implement DISEqC and multipoint LNBf's don't need to
control the voltage level, provided that either 13V or 18V is sent to
power up the LNBf.

.. attention:: if more than one device is connected to the same antenna,
   setting a voltage level may interfere on other devices, as they may lose
   the capability of setting polarization or IF. So, on those cases, setting
   the voltage to SEC_VOLTAGE_OFF while the device is not is used is
   recommended.


Return Value
============

On success 0 is returned, on error -1 and the ``errno`` variable is set
appropriately. The generic error codes are described at the
:ref:`Generic Error Codes <gen-errors>` chapter.
Commit	Line	Data
5377d91f MH	1	.. -- coding: utf-8; mode: rst --
	2
	3	.. _FE_SET_VOLTAGE:
	4
	5	********************
	6	ioctl FE_SET_VOLTAGE
	7	********************
	8
15e7d615	9	Name
586027ce	10	====
5377d91f	11
586027ce	12	FE_SET_VOLTAGE - Allow setting the DC level sent to the antenna subsystem.
5377d91f	13
15e7d615 MCC	14
15e7d615 MCC	15	Synopsis
5377d91f MH	16	========
5377d91f MH	17
cf8076c3 MCC	18	.. c:function:: int ioctl( int fd, FE_SET_VOLTAGE, enum fe_sec_voltage *voltage )
cf8076c3 MCC	19	:name: FE_SET_VOLTAGE
5377d91f	20
586027ce	21
15e7d615	22	Arguments
5377d91f MH	23	=========
	24
	25	``fd``
	26	File descriptor returned by :ref:`open() <frontend_f_open>`.
	27
5377d91f	28	``voltage``
836cf1db	29	pointer to enum :c:type:`fe_sec_voltage`
5377d91f MH	30
5377d91f MH	31	Valid values are described at enum
836cf1db	32	:c:type:`fe_sec_voltage`.
5377d91f MH	33
5377d91f MH	34
15e7d615	35	Description
5377d91f MH	36	===========
	37
	38	This ioctl allows to set the DC voltage level sent through the antenna
	39	cable to 13V, 18V or off.
	40
	41	Usually, a satellite antenna subsystems require that the digital TV
	42	device to send a DC voltage to feed power to the LNBf. Depending on the
	43	LNBf type, the polarization or the intermediate frequency (IF) of the
	44	LNBf can controlled by the voltage level. Other devices (for example,
	45	the ones that implement DISEqC and multipoint LNBf's don't need to
	46	control the voltage level, provided that either 13V or 18V is sent to
	47	power up the LNBf.
	48
706f8a99 MCC	49	.. attention:: if more than one device is connected to the same antenna,
	50	setting a voltage level may interfere on other devices, as they may lose
	51	the capability of setting polarization or IF. So, on those cases, setting
	52	the voltage to SEC_VOLTAGE_OFF while the device is not is used is
	53	recommended.
5377d91f	54
586027ce	55
15e7d615	56	Return Value
586027ce	57	============
5377d91f MH	58
	59	On success 0 is returned, on error -1 and the ``errno`` variable is set
	60	appropriately. The generic error codes are described at the
	61	:ref:`Generic Error Codes <gen-errors>` chapter.