Driver Model
| +---------------------------------------------------------------+
S | | 'gpm -t msc -m /var/run/lirc/lircm' or a well configured X |
O | | (see section 'Configuring lircmd') for details |
F | +--------------+------------------------------------------------+
T | |
W | /var/run/lirc/lircm (named pipe (FIFO) ==> one connection)
A | |
R | +-----------+-----------+ +----------------------------------+
E | | mouse daemon (lircmd) | | tools (irexec, irxevent, ...) |
| | configured with | | configured with ~/.config/lircrc |
| | lircmd.conf | | |
| +-----------+-----------+ +-----------+----------------------+
| | |
| +-------------+-------------+
| |
| /var/run/lirc/lircd (socket ==> multiple connections)
| |
S | +----------------+--------------------------+
O | | decoder daemon (lircd), irrecord or mode2 | TCP/IP
F | | lircd is configured through lircd.conf +--- port
T | User space | | 8765
W | +------------------+------------------------+
A | | |
R | | |
E | | |
| | /dev/uinput (Linux input layer)
| |
| |
+---------------------------------+----------------------------------
| Kernel space | (character device
| | driver ==>
| +------------+----------+ one connection)
| | |
| /dev/lirc /dev/ttySx
| | |
| +------------+-------------+ +-----+---------------+
| | LIRC device driver | | Linux serial driver |
| | (with ioctl-interface) | | |
| +------------+-------------+ +----------+----------+
| | |
--+--------------------+----------------------------+------------------
| | |
| +----------+------------+ |
| | | |
| +-------+----------------+ +----+-----+ +-------+-----------------+
H | | serial / parallel port | | TV cards | | Irman/RemoteMaster/etc. |
W | +------------------------+ +----------+ +-------------------------+
|
Formats
Writing TV card drivers using lirc_dev
The lirc_dev module is a helper and abstraction layer
for other modules. It registers /dev/lirc device in a
system (including support for devfs) and waits for plugin
registration. After that it serves device requests (open, read,
poll, ioctl, close) and if needed calls callback functions from
plugin(s) to communicate with the physical device.
Plugins can be registered and unregistered many times. The
current implementation allows two concurrent plugins, but can be
easily changed by increasing the MAX_IRCTL_DEVICES
definition. It also allows receiving of scan codes, which have
more than 8 bits. Current limit for a scan code is 16*8 bits and
also can be changed by increasing the BUFLEN definition.
For an API description see lirc_dev.h. The lirc_gpio
module can be treated as examples of using this API. This
code contains many lines with debug messages (activated by
debug option) and they will sustain until more tests
will be performed.
Warning: Due to the used kernel API it requires kernel
2.2.4 or higher. Any suggestions and questions are
welcome. Artur
Lipowski
Writing Applications for LIRC
As LIRC is able to both receive and send IR commands there are
two possible types of applications. Programs that send IR
commands like xrc and irsend or programs that
receive commands like irexec, irxevent and
irpty. Both types of applications will have to connect
to the lircd daemon using the socket interface usually located
in /var/run/lirc/lircd. Communication on the socket uses human
readable format. The end of a line is indicated by a newline
character.
Whenever lircd receives a IR signal it will broadcast the
following string to each client:
<code> <repeat count> <button name> <remote control name>
code is a 64-bit encoding (in hexadecimal
representation) of the IR signal. It's usage in applications is
deprecated and should be ignored. The repeat count
shows how long the user has been holding down a button. The
counter will start at 0 and increment each time a new IR signal
has been received. The button name and remote
control name are defined in the lircd config file. Their
purpose should be quite self-explanatory. They must not contain
any whitespace.
The only other situation when lircd broadcasts to all clients is
when it receives the SIGHUP signal and successfully re-reads its
config file. Then it will send a SIGHUP packet to its clients
indicating that its configuration might have changed. This
feature is e.g. used in xrc to rebuild the
list of supported remote controls each time lircd's
configuration changes. The format of the packet will be
explained later.
NOTE: As of 0.9.2+, this way of sending data is obsolete since
sending is supported directly in the API. See the API documentation,
Applications that want to send out IR commands can use the
following commands:
SEND_ONCE <remote control name> <button name> [<repeat count>]
SEND_START <remote control name> <button name>
SEND_STOP <remote control name> <button name>
The SEND_ONCE directive tells lircd to send the IR signal
associated with the given remote control and button name, and then
repeat it repeat count times. repeat count is
a decimal number between 0 and repeat_max. The latter
can be given as a command line argument to lircd, and defaults
to 600. If repeat count is
not specified or is less than the minimum number of repeats
for the selected remote control, the minimum value will be
used. SEND_START tells lircd to start repeating the
given button until it receives a SEND_STOP command. However, the
number of repeats is limited to repeat_max. lircd
won't accept any new send commands while it is repeating.
lircd also understands the following commands:
VERSION
LIST [<remote control name>]
The response to the VERSION command will be a packet containing
lircd's version.
The LIST command without further arguments can be used to get a
list of all remote controls known to lircd. If a name of a
supported remote control is given as argument all buttons of the
given remote control are listed in the reply packet. Have a look
at xrc for an example how this can be used.
There still remains to explain the format of lircd's reply
packets. Here is a formal description of the packets:
BEGIN
<command>
[SUCCESS|ERROR]
[DATA
n
n lines of data]
END
The protocol guarantees that broadcasted messages won't
interfere with reply packets. But broadcasts may appear at any
point between packets. command is the command lircd is
currently processing. Its an exact copy of the command the
client application has sent. The only exception are SIGHUP
packages where command is substituted with SIGHUP. Note
that SIGHUP packages may appear just after you have sent a
command to lircd, so you have to make sure you don't confuse
them with replies. SIGHUP packages come without any further data
while each reply to a command contains either SUCCESS or ERROR
indicating the result of processing the command. In case of an
error the following data is a message explaining the
problem. This message can be used to create an error message for
the user.
If the command was successful, data is only sent for the
commands that return some information. Note that a packet
containing 0 lines of data can be a valid reply.
The lirc_client library
If you only want to make your application to send or receive
IR commands and if you don't want to mess with all the protocol stuff
you can use the lirc_client api.
lircrcd protocol
lircrcd syntactically uses the same protocol as lircd described
in the last section. It supports the following commands:
- IDENT ident
-
Each program connecting to lircrcd identifies itself using
this program. ident is the string that is used in
the prog token inside the .lircrc file.
- CODE code
-
When the client receives the code string from lircd
it will send it to lircrcd and will receive back the
applicable config string from the .lircrc config file. It
should resend the CODE command until nothing is returned
back which means that nothing (more) should happen in
response to code. This command is used each time
the lirc_code2char() function is called by a client.
- GETMODE
-
lircrcd will return the current mode string.
Hardware Abstraction Layer (HAL) integration
If your system support the FreeDesktop Hardware Abstraction Layer (HAL),
you will want to install the file contrib/hal/20-ircontrol-lirc.fdi in
${datarootdir}/hal/fdi/information/20thirdparty
This file can be generated at will using contrib/hal/gen-hal-fdi.pl.
Installing 20-ircontrol-lirc.fdi allow applications developers to detect
USB remotes easily by searching for HAL devices with info.capabilities=input.remote_control
This is a work in progress. We will also provide more information in the
future, such as the driver/manufacturer/device name(s), and possibly
event reporting.
Note for configuration application developers
If you want to make a configuration application, lirc provides
a parseable list of LIRC supported devices.
This file is generated at compilation time, along with its HTML
equivalent and is available as doc/lirc.hwdb in the source tree.
It should also be installed by the binary packages of your prefered
distribution (bug report otherwise!).
The format is:
[remote controls type]
description;driver;lirc driver;HW_DEFAULT;lircd_conf;
The HW_DEFAULT entry is always empty.
Known bugs
-
The general lirc bugtracker is at the
sourceforge
website.
If you use the lirc_serial or
lirc_parallel driver regularly to transmit
infra-red signals you might notice that your system clock
will slow down. During transmit the driver turns off
interrupts and hence some clock interrupts might get lost
causing system clock inaccuracy. Unfortunately in order to
ensure a good signal timing interrupts have to be
disabled. Currently no work-around is known for this problem
except using a program like netdate to synchronize
your system clock regularly.
-
The lirc_serial and lirc_parallel drivers
measure the time between interrupts on the serial resp.
parallel port to get a pulse and space representation of the
incoming infra-red signal. If interrupts are disabled by the
CPU for a rather long time (>100 µs, which happens
often e.g. during heavy IDE disk activity) some interrupts
might get lost and the incoming data stream becomes
disturbed. In this case decoding of the infra-red signal
will fail. This is the downside of the really simple
receiver circuits and can't be addressed in software except
keeping the time where interrupts are disabled to a minimum.
If you are using an IDE system you might want to try calling
hdparm -u1 -d1 for all of your drives. This enables
DMA for the drive and allows the driver to unmask other
interrupts during handling of a disk interrupt. But be aware
that this can be dangerous for some (buggy) IDE
chipsets. Consult the hdparm man page for further
information.
[LIRC homepage]
The LIRC Manual, last update: 10-June-2014
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