mirror of https://github.com/mkerrisk/man-pages
438 lines
13 KiB
Groff
438 lines
13 KiB
Groff
.\" Copyright (c) 2015-2016, Alec Leamas
|
|
.\" Copyright (c) 2018, Sean Young <sean@mess.org>
|
|
.\"
|
|
.\" %%%LICENSE_START(GPLv2+_DOC_FULL)
|
|
.\" This is free documentation; you can redistribute it and/or
|
|
.\" modify it under the terms of the GNU General Public License as
|
|
.\" published by the Free Software Foundation; either version 2 of
|
|
.\" the License, or (at your option) any later version.
|
|
.\"
|
|
.\" The GNU General Public License's references to "object code"
|
|
.\" and "executables" are to be interpreted as the output of any
|
|
.\" document formatting or typesetting system, including
|
|
.\" intermediate and printed output.
|
|
.\"
|
|
.\" This manual is distributed in the hope that it will be useful,
|
|
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
.\" GNU General Public License for more details.
|
|
.\"
|
|
.\" You should have received a copy of the GNU General Public
|
|
.\" License along with this manual; if not, see
|
|
.\" <http://www.gnu.org/licenses/>.
|
|
.\" %%%LICENSE_END
|
|
.TH LIRC 4 2019-03-06 "Linux" "Linux Programmer's Manual"
|
|
.SH NAME
|
|
lirc \- lirc devices
|
|
.SH DESCRIPTION
|
|
The
|
|
.I /dev/lirc*
|
|
character devices provide a low-level
|
|
bidirectional interface to infra-red (IR) remotes.
|
|
Most of these devices can receive, and some can send.
|
|
When receiving or sending data, the driver works in two different modes
|
|
depending on the underlying hardware.
|
|
.PP
|
|
Some hardware (typically TV-cards) decodes the IR signal internally
|
|
and provides decoded button presses as scancode values.
|
|
Drivers for this kind of hardware work in
|
|
.BR LIRC_MODE_SCANCODE
|
|
mode.
|
|
Such hardware usually does not support sending IR signals.
|
|
Furthermore, such hardware can only decode a limited set of IR protocols,
|
|
usually only the protocol of the specific remote which is
|
|
bundled with, for example, a TV-card.
|
|
.PP
|
|
Other hardware provides a stream of pulse/space durations.
|
|
Such drivers work in
|
|
.BR LIRC_MODE_MODE2
|
|
mode.
|
|
Sometimes, this kind of hardware also supports
|
|
sending IR data.
|
|
Such hardware can be used with (almost) any kind of remote.
|
|
This type of hardware can also be used in
|
|
.BR LIRC_MODE_SCANCODE
|
|
mode, in which case the kernel IR decoders will decode the IR.
|
|
These decoders can be written in extended BPF (see
|
|
.BR bpf (2))
|
|
and attached to the
|
|
.B lirc
|
|
device.
|
|
.PP
|
|
The \fBLIRC_GET_FEATURES\fR ioctl (see below) allows probing for whether
|
|
receiving and sending is supported, and in which modes, amongst other
|
|
features.
|
|
.\"
|
|
.SS Reading input with the LIRC_MODE_MODE2 mode
|
|
In the \fBLIRC_MODE_MODE2 mode\fR, the data returned by
|
|
.BR read (2)
|
|
provides 32-bit values representing a space or a pulse duration.
|
|
The time of the duration (microseconds) is encoded in the lower 24 bits.
|
|
The upper 8 bits indicate the type of package:
|
|
.TP 4
|
|
.BR LIRC_MODE2_SPACE
|
|
Value reflects a space duration (microseconds).
|
|
.TP 4
|
|
.BR LIRC_MODE2_PULSE
|
|
Value reflects a pulse duration (microseconds).
|
|
.TP 4
|
|
.BR LIRC_MODE2_FREQUENCY
|
|
Value reflects a frequency (Hz); see the
|
|
.B LIRC_SET_MEASURE_CARRIER_MODE
|
|
ioctl.
|
|
.TP 4
|
|
.BR LIRC_MODE2_TIMEOUT
|
|
Value reflects a space duration (microseconds).
|
|
The package reflects a timeout; see the
|
|
.B LIRC_SET_REC_TIMEOUT_REPORTS
|
|
ioctl.
|
|
.\"
|
|
.SS Reading input with the LIRC_MODE_SCANCODE mode
|
|
In the \fBLIRC_MODE_SCANCODE\fR
|
|
mode, the data returned by
|
|
.BR read (2)
|
|
reflects decoded button presses, in the struct \fIlirc_scancode\fR.
|
|
The scancode is stored in the \fIscancode\fR field, and the IR protocol
|
|
is stored in \fIrc_proto\fR.
|
|
This field has one the values of the \fIenum rc_proto\fR.
|
|
.\"
|
|
.SS Writing output with the LIRC_MODE_PULSE mode
|
|
The data written to the character device using
|
|
.BR write (2)
|
|
is a pulse/space sequence of integer values.
|
|
Pulses and spaces are only marked implicitly by their position.
|
|
The data must start and end with a pulse, thus it must always include
|
|
an odd number of samples.
|
|
The
|
|
.BR write (2)
|
|
function blocks until the data has been transmitted by the
|
|
hardware.
|
|
If more data is provided than the hardware can send, the
|
|
.BR write (2)
|
|
call fails with the error
|
|
.BR EINVAL .
|
|
.SS Writing output with the LIRC_MODE_SCANCODE mode
|
|
The data written to the character devices must be a single struct
|
|
\fIlirc_scancode\fR.
|
|
The \fIscancode\fR and \fIrc_proto\fR fields must
|
|
filled in, all other fields must be 0.
|
|
The kernel IR encoders will
|
|
convert the scancode to pulses and spaces.
|
|
The protocol or scancode is invalid, or the
|
|
.B lirc
|
|
device cannot transmit.
|
|
.SH IOCTL COMMANDS
|
|
The LIRC device's ioctl definition is bound by the ioctl function
|
|
definition of
|
|
.IR "struct file_operations" ,
|
|
leaving us with an
|
|
.IR "unsigned int"
|
|
for the ioctl command and an
|
|
.IR "unsigned long"
|
|
for the argument.
|
|
For the purposes of ioctl portability across 32-bit and 64-bit architectures,
|
|
these values are capped to their 32-bit sizes.
|
|
.PP
|
|
.nf
|
|
#include <linux/lirc.h> /* But see BUGS */
|
|
int ioctl(int fd, int cmd, ...);
|
|
.fi
|
|
.PP
|
|
The following ioctls can be used to probe or change specific
|
|
.B lirc
|
|
hardware settings.
|
|
Many require a third argument, usually an
|
|
.IR int ,
|
|
referred to below as
|
|
.IR val .
|
|
.\"
|
|
.SS Always Supported Commands
|
|
\fI/dev/lirc*\fR devices always support the following commands:
|
|
.TP 4
|
|
.BR LIRC_GET_FEATURES " (\fIvoid\fP)"
|
|
Returns a bit mask of combined features bits; see FEATURES.
|
|
.PP
|
|
If a device returns an error code for
|
|
.BR LIRC_GET_FEATURES ,
|
|
it is safe to assume it is not a
|
|
.B lirc
|
|
device.
|
|
.\"
|
|
.SS Optional Commands
|
|
Some
|
|
.B lirc
|
|
devices support the commands listed below.
|
|
Unless otherwise stated, these fail with the error \fBENOTTY\fR if the
|
|
operation isn't supported, or with the error \fBEINVAL\fR if the operation
|
|
failed, or invalid arguments were provided.
|
|
If a driver does not announce support of certain features, invoking
|
|
the corresponding ioctls will fail with the error
|
|
.BR ENOTTY .
|
|
.TP
|
|
.BR LIRC_GET_REC_MODE " (\fIvoid\fP)"
|
|
If the
|
|
.B lirc
|
|
device has no receiver, this operation fails with the error
|
|
.BR ENOTTY .
|
|
Otherwise, it returns the receive mode, which will be one of:
|
|
.RS
|
|
.TP
|
|
.BR LIRC_MODE_MODE2
|
|
The driver returns a sequence of pulse/space durations.
|
|
.TP
|
|
.BR LIRC_MODE_SCANCODE
|
|
The driver returns struct
|
|
.I lirc_scancode
|
|
values, each of which represents
|
|
a decoded button press.
|
|
.RE
|
|
.TP
|
|
.BR LIRC_SET_REC_MODE " (\fIint\fP)"
|
|
Set the receive mode.
|
|
.IR val
|
|
is either
|
|
.BR LIRC_MODE_SCANCODE
|
|
or
|
|
.BR LIRC_MODE_MODE2 .
|
|
If the
|
|
.B lirc
|
|
device has no receiver, this operation fails with the error
|
|
.B ENOTTY.
|
|
.TP
|
|
.BR LIRC_GET_SEND_MODE " (\fIvoid\fP)"
|
|
Return the send mode.
|
|
.BR LIRC_MODE_PULSE
|
|
or
|
|
.BR LIRC_MODE_SCANCODE
|
|
is supported.
|
|
If the
|
|
.B lirc
|
|
device cannot send, this operation fails with the error
|
|
.B ENOTTY.
|
|
.TP
|
|
.BR LIRC_SET_SEND_MODE " (\fIint\fP)"
|
|
Set the send mode.
|
|
.IR val
|
|
is either
|
|
.BR LIRC_MODE_SCANCODE
|
|
or
|
|
.BR LIRC_MODE_PULSE .
|
|
If the
|
|
.B lirc
|
|
device cannot send, this operation fails with the error
|
|
.BR ENOTTY .
|
|
.TP
|
|
.BR LIRC_SET_SEND_CARRIER " (\fIint\fP)"
|
|
Set the modulation frequency.
|
|
The argument is the frequency (Hz).
|
|
.TP
|
|
.BR LIRC_SET_SEND_DUTY_CYCLE " (\fIint\fP)"
|
|
Set the carrier duty cycle.
|
|
.I val
|
|
is a number in the range [0,100] which
|
|
describes the pulse width as a percentage of the total cycle.
|
|
Currently, no special meaning is defined for 0 or 100, but the values
|
|
are reserved for future use.
|
|
.IP
|
|
.TP
|
|
.BR LIRC_GET_MIN_TIMEOUT " (\fIvoid\fP)", " "\
|
|
LIRC_GET_MAX_TIMEOUT " (\fIvoid\fP)"
|
|
Some devices have internal timers that can be used to detect when
|
|
there has been no IR activity for a long time.
|
|
This can help
|
|
.BR lircd (8)
|
|
in detecting that an IR signal is finished and can speed up the
|
|
decoding process.
|
|
These operations
|
|
return integer values with the minimum/maximum timeout that can be
|
|
set (microseconds).
|
|
Some devices have a fixed timeout.
|
|
For such drivers,
|
|
.BR LIRC_GET_MIN_TIMEOUT
|
|
and
|
|
.BR LIRC_GET_MAX_TIMEOUT
|
|
will fail with the error
|
|
.BR ENOTTY .
|
|
.TP
|
|
.BR LIRC_SET_REC_TIMEOUT " (\fIint\fP)"
|
|
Set the integer value for IR inactivity timeout (microseconds).
|
|
To be accepted, the value must be within the limits defined by
|
|
.BR LIRC_GET_MIN_TIMEOUT
|
|
and
|
|
.BR LIRC_GET_MAX_TIMEOUT .
|
|
A value of 0 (if supported by the hardware) disables all hardware
|
|
timeouts and data should be reported as soon as possible.
|
|
If the exact value cannot be set, then the next possible value
|
|
.I greater
|
|
than the given value should be set.
|
|
.TP
|
|
.BR LIRC_GET_REC_TIMEOUT " (\fIvoid\fP)"
|
|
Return the current inactivity timeout (microseconds).
|
|
Available since Linux 4.18.
|
|
.TP
|
|
.BR LIRC_SET_REC_TIMEOUT_REPORTS " (\fIint\fP)"
|
|
Enable
|
|
.RI ( val
|
|
is 1) or disable
|
|
.RI ( val
|
|
is 0) timeout packages in
|
|
.BR LIRC_MODE_MODE2 .
|
|
The behavior of this operation has varied across kernel versions:
|
|
.RS
|
|
.IP * 3
|
|
Since Linux 4.16: each time the
|
|
.B lirc device is opened,
|
|
timeout reports are by default enabled for the resulting file descriptor.
|
|
The
|
|
.B LIRC_SET_REC_TIMEOUT
|
|
operation can be used to disable (and, if desired, to later re-enable)
|
|
the timeout on the file descriptor.
|
|
.IP *
|
|
In Linux 4.15 and earlier:
|
|
timeout reports are disabled by default, and enabling them (via
|
|
.BR LIRC_SET_REC_TIMEOUT )
|
|
on any file descriptor associated with the
|
|
.B lirc
|
|
device has the effect of enabling timeouts for all file descriptors
|
|
referring to that device (until timeouts are disabled again).
|
|
.RE
|
|
.TP
|
|
.BR LIRC_SET_REC_CARRIER " (\fIint\fP)"
|
|
Set the upper bound of the receive carrier frequency (Hz).
|
|
See
|
|
.BR LIRC_SET_REC_CARRIER_RANGE .
|
|
.TP
|
|
.BR LIRC_SET_REC_CARRIER_RANGE " (\fIint\fP)"
|
|
Sets the lower bound of the receive carrier frequency (Hz).
|
|
For this to take affect, first set the lower bound using the
|
|
.BR LIRC_SET_REC_CARRIER_RANGE
|
|
ioctl, and then the upper bound using the
|
|
.BR LIRC_SET_REC_CARRIER
|
|
ioctl.
|
|
.TP
|
|
.BR LIRC_SET_MEASURE_CARRIER_MODE " (\fIint\fP)"
|
|
Enable
|
|
.RI ( val
|
|
is 1) or disable
|
|
.RI ( val
|
|
is 0) the measure mode.
|
|
If enabled, from the next key press on, the driver will send
|
|
.BR LIRC_MODE2_FREQUENCY
|
|
packets.
|
|
By default, this should be turned off.
|
|
.TP
|
|
.BR LIRC_GET_REC_RESOLUTION " (\fIvoid\fP)"
|
|
Return the driver resolution (microseconds).
|
|
.TP
|
|
.BR LIRC_SET_TRANSMITTER_MASK " (\fIint\fP)"
|
|
Enable the set of transmitters specified in
|
|
.IR val ,
|
|
which contains a bit mask where each enabled transmitter is a 1.
|
|
The first transmitter is encoded by the least significant bit, and so on.
|
|
When an invalid bit mask is given, for example a bit is set even
|
|
though the device does not have so many transmitters,
|
|
this operation returns the
|
|
number of available transmitters and does nothing otherwise.
|
|
.TP
|
|
.BR LIRC_SET_WIDEBAND_RECEIVER " (\fIint\fP)"
|
|
Some devices are equipped with a special wide band receiver which is
|
|
intended to be used to learn the output of an existing remote.
|
|
This ioctl can be used to enable
|
|
.RI ( val
|
|
equals 1) or disable
|
|
.RI ( val
|
|
equals 0) this functionality.
|
|
This might be useful for devices that otherwise have narrow band
|
|
receivers that prevent them to be used with certain remotes.
|
|
Wide band receivers may also be more precise.
|
|
On the other hand, their disadvantage usually is reduced range of
|
|
reception.
|
|
.IP
|
|
Note: wide band receiver may be implicitly enabled if you enable
|
|
carrier reports.
|
|
In that case, it will be disabled as soon as you disable carrier reports.
|
|
Trying to disable a wide band receiver while carrier reports are active
|
|
will do nothing.
|
|
.\"
|
|
.SH FEATURES
|
|
the
|
|
.BR LIRC_GET_FEATURES
|
|
ioctl returns a bit mask describing features of the driver.
|
|
The following bits may be returned in the mask:
|
|
.TP
|
|
.BR LIRC_CAN_REC_MODE2
|
|
The driver is capable of receiving using
|
|
.BR LIRC_MODE_MODE2 .
|
|
.TP
|
|
.BR LIRC_CAN_REC_SCANCODE
|
|
The driver is capable of receiving using
|
|
.BR LIRC_MODE_SCANCODE .
|
|
.TP
|
|
.BR LIRC_CAN_SET_SEND_CARRIER
|
|
The driver supports changing the modulation frequency using
|
|
.BR LIRC_SET_SEND_CARRIER .
|
|
.TP
|
|
.BR LIRC_CAN_SET_SEND_DUTY_CYCLE
|
|
The driver supports changing the duty cycle using
|
|
.BR LIRC_SET_SEND_DUTY_CYCLE .
|
|
.TP
|
|
.BR LIRC_CAN_SET_TRANSMITTER_MASK
|
|
The driver supports changing the active transmitter(s) using
|
|
.BR LIRC_SET_TRANSMITTER_MASK .
|
|
.TP
|
|
.BR LIRC_CAN_SET_REC_CARRIER
|
|
The driver supports setting the receive carrier frequency using
|
|
.BR LIRC_SET_REC_CARRIER .
|
|
Any
|
|
.B lirc
|
|
device since the drivers were merged in kernel release 2.6.36
|
|
must have
|
|
.BR LIRC_CAN_SET_REC_CARRIER_RANGE
|
|
set if
|
|
.BR LIRC_CAN_SET_REC_CARRIER
|
|
feature is set.
|
|
.TP
|
|
.BR LIRC_CAN_SET_REC_CARRIER_RANGE
|
|
The driver supports
|
|
.BR LIRC_SET_REC_CARRIER_RANGE .
|
|
The lower bound of the carrier must first be set using the
|
|
.BR LIRC_SET_REC_CARRIER_RANGE
|
|
ioctl, before using the
|
|
.BR LIRC_SET_REC_CARRIER
|
|
ioctl to set the upper bound.
|
|
.TP
|
|
.BR LIRC_CAN_GET_REC_RESOLUTION
|
|
The driver supports
|
|
.BR LIRC_GET_REC_RESOLUTION .
|
|
.TP
|
|
.BR LIRC_CAN_SET_REC_TIMEOUT
|
|
The driver supports
|
|
.BR LIRC_SET_REC_TIMEOUT .
|
|
.TP
|
|
.BR LIRC_CAN_MEASURE_CARRIER
|
|
The driver supports measuring of the modulation frequency using
|
|
.BR LIRC_SET_MEASURE_CARRIER_MODE .
|
|
.TP
|
|
.BR LIRC_CAN_USE_WIDEBAND_RECEIVER
|
|
The driver supports learning mode using
|
|
.BR LIRC_SET_WIDEBAND_RECEIVER .
|
|
.TP
|
|
.BR LIRC_CAN_SEND_PULSE
|
|
The driver supports sending using
|
|
.BR LIRC_MODE_PULSE
|
|
or
|
|
.BR LIRC_MODE_SCANCODE
|
|
.\"
|
|
.SH BUGS
|
|
Using these devices requires the kernel source header file
|
|
.IR lirc.h .
|
|
This file is not available before kernel release 4.6.
|
|
Users of older kernels could use the file bundled in
|
|
.UR http://www.lirc.org
|
|
.UE .
|
|
.\"
|
|
.SH SEE ALSO
|
|
\fBir\-ctl\fP(1), \fBlircd\fP(8),\ \fBbpf\fP(2)
|
|
.PP
|
|
https://www.kernel.org/doc/html/latest/media/uapi/rc/lirc-dev.html
|