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<!-- Overview ----------------------------------------------------------->
<A NAME="overview"><HR></A>
<CENTER><H1>Driver Model</H1></CENTER>
<HR WIDTH="70%">
<PRE>
| +------------------------------------------------------+
S | | 'gpm -t msc -m /dev/lircm' or a well configured X |
O | | (see section 'Configuring lircmd') for details |
F | +--------------+---------------------------------------+
T | |
W | /dev/lircm (named pipe (FIFO) ==> one connection)
A | |
R | +-----------+-----------+ +-------------------------------+
E | | mouse daemon (lircmd) | | tools (irexec, irxevent, ...) |
| | configured with | | configured with ~/.lircrc |
| | lircmd.conf | | |
| +-----------+-----------+ +-----------+-------------------+
| | |
| +-------------+-------------+
| |
| /dev/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 | |
| |
| |
| |
+---------------------------------+----------------------------------
| 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 | +------------------------+ +----------+ +-------------------------+
|
</PRE>
<A NAME="formats"><HR></A>
<H1 ALIGN="CENTER">Formats</H1>
<HR WIDTH="70%">
<UL>
<LI><B>/dev/lirc:</B><BR>
<P>
highly depends on the mode selected with ioctls:
</P>
<DL>
<DT>LIRC_MODE_MODE2</DT>
<DD>
<P>
outputs packets containing an int value describing a IR signal<BR>
<UL>
<LI>bits 0-23 contain the length of the pulse/space in
microseconds</LI>
<LI>bit 24 is either 0, meaning space, or 1, meaning
pulse</LI>
<LI>all other bits are unused</LI>
</UL>
Lengths greater than or equal to 16 seconds are clamped to
0xffffff.
</P>
<P>References:
<UL>
<LI>drivers/lirc_serial/lirc_serial.c</LI>
<LI>drivers/lirc_parallel/lirc_parallel.c</LI>
<LI>tools/mode2.c (dumps the output from the driver to stdout)</LI>
</UL>
</P>
</DD>
<DT>LIRC_MODE_CODE</DT>
<DD>
<P>
outputs chars (8 bits)
</P>
</DD>
<DT>LIRC_MODE_LIRCCODE</DT>
<DD>
<P>
outputs codes of configurable length in big endian byte order
</P>
</DD>
</DL>
</LI>
<LI><B>/dev/lircd:</B><BR>
outputs strings containing all information about the remote and the
pressed button.
<P>References:
<UL>
<LI>daemons/lircd.c</LI>
<LI>tools/irw.c</LI>
</UL></P>
</LI>
<LI><B>/dev/lircm:</B><BR>
<UL>
<LI>MouseSystems<BR>
5 byte packets:
<UL>
<LI>byte 1: button information</LI>
<LI>byte 2: change on X axis</LI>
<LI>byte 3: change on Y axis</LI>
<LI>byte 4,5: 0</LI>
</UL>
</LI>
<LI>IMPS/2<BR>
4 byte packets: check the source code for details
</LI>
</UL>
<P>References:
<UL>
<LI>daemons/lircmd.c</LI>
</UL></P>
</LI>
</UL>
<A NAME="lirc_dev"><HR></A>
<H1 ALIGN="CENTER">Writing TV card drivers using lirc_dev</H1>
<HR WIDTH="70%">
<P>
The <em>lirc_dev</em> module is a helper and abstraction layer for
other modules. It registers <em>/dev/lirc</em> 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.
</P>
<P>
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.
</P>
<P>
For an API description see <em>lirc_dev.h</em>. The lirc_gpio module
can be treated as examples of using this API.<br>
This code contains many lines with debug messages (activated by
<em>debug</em> option) and they will sustain until more tests will be
performed.
</P>
<P>
<B>Warning:</B> Due to the used kernel API it requires kernel 2.2.4 or
higher.<br>
Any suggestions and questions are welcome. <A
href="mailto:alipowski@kki.net.pl">Artur Lipowski</A>
</P>
<!-- Writing LIRC Applications ------------------------------------------>
<A NAME="applications"><HR></A>
<H1 ALIGN="CENTER">Writing Applications for LIRC</H1>
<HR WIDTH="70%">
<P>
As LIRC is able to both receive and send IR commands there are two
possible types of applications. Programs that send IR commands like
<em>xrc</em> and <em>rc</em> or programs that receive commands like
<em>irexec</em>, <em>irxevent</em> and <em>irpty</em>. Both types of
applications will have to connect to the lircd daemon using the socket
interface usually located in /dev/lircd. Communication on the socket
uses human readable format. The end of a line is indicated by a
newline character.
</P>
<P>
Whenever lircd receives a IR signal it will broadcast the following
string to each client:
<PRE>
&lt;code&gt; &lt;repeat count&gt; &lt;button name&gt; &lt;remote control name&gt;
</PRE>
<em>code</em> is a 64-bit encoding (in hexadecimal representation) of
the IR signal. It's usage in applications is deprecated and should be
ignored. The <em>repeat count</em> 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 <em>button name</em> and
<em>remote control name</em> are defined in the lircd config
file. Their purpose should be quite self-explanatory. They must not
contain any whitespace.<BR>
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
<NOBR>e.g.</NOBR> used in <em>xrc</em> to rebuild the list of
supported remote controls each time lircd's configuration changes. The
format of the packet will be explained later.
</P>
<P>
Applications that want to send out IR commands can use the following
commands:
<PRE>
SEND_ONCE &lt;remote control name&gt; &lt;button name&gt;
SEND_START &lt;remote control name&gt; &lt;button name&gt;
SEND_STOP &lt;remote control name&gt; &lt;button name&gt;
</PRE>
The SEND_ONCE directive tells lircd to send the IR signal associated
with the given remote control and button name once. Consequently
SEND_START tells lircd to start repeating the given button until it
receives a SEND_STOP command. As repeating of IR signals is very CPU
intensive on most systems there should be a limit on the time for
repeating buttons in every application. The number of repeats is
internally limited to 600 which for most remotes is equal to one
minute of repeating. lircd won't accept any new send commands while it
is repeating.
</P>
<P>
lircd also understands the following commands:
<PRE>
VERSION
LIST [&lt;remote control name&gt;]
</PRE>
The response to the VERSION command will be a packet containing
lircd's version.<BR>
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 <em>xrc</em> for an
example how this can be used.
</P>
<P>
There still remains to explain the format of lircd's reply
packets. Here is a formal description of the packets:
<PRE>
BEGIN
&lt;command&gt;
[SUCCESS|ERROR]
[DATA
n
n lines of data]
END
</PRE>
The protocol guarantees that broadcasted messages won't interfere with
reply packets. But broadcasts may appear at any point between
packets. <em>command</em> 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
<em>command</em> 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.<BR>
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.
</P>
<!-- Writing LIRC Applications ------------------------------------------>
<A NAME="library"><HR></A>
<H2 ALIGN="CENTER">The lirc_client library</H2>
<HR WIDTH="70%">
<P>
If you only want to make your application receive IR commands and if
you don't want to mess with all the protocol stuff you can use the
<em>lirc_client</em> library that comes with LIRC since version
0.6.0. With the help of this library your program can look as simple
as this:
<PRE>
/* &#36;Id: irexec.c,v 5.2 2000/02/02 20:28:42 columbus Exp $ */
/****************************************************************************
** irexec.c ****************************************************************
****************************************************************************
*
* irexec - execute programs according to the pressed remote control buttons
*
* Copyright (C) 1998 Trent Piepho &lt;xyzzy@u.washington.edu&gt;
* Copyright (C) 1998 Christoph Bartelmus &lt;lirc@bartelmus.de&gt;
*
*/
#ifdef HAVE_CONFIG_H
# include &lt;config.h&gt;
#endif
#include &lt;errno.h&gt;
#include &lt;unistd.h&gt;
#include &lt;stdarg.h&gt;
#include &lt;stdio.h&gt;
#include &lt;stdlib.h&gt;
#include &lt;string.h&gt;
#include "lirc_client.h"
char *progname;
int main(int argc, char *argv[])
{
struct lirc_config *config;
progname=argv[0];
if(argc&gt;2)
{
fprintf(stderr,"Usage: %s &lt;config file&gt;\n",progname);
exit(EXIT_FAILURE);
}
if(lirc_init("irexec",1)==-1) exit(EXIT_FAILURE);
if(lirc_readconfig(argc==2 ? argv[1]:NULL,&config,NULL)==0)
{
char *code;
char *c;
int ret;
while(lirc_nextcode(&code)==0)
{
if(code==NULL) continue;
while((ret=lirc_code2char(config,code,&c))==0 &&
c!=NULL)
{
#ifdef DEBUG
printf("Execing command \"%s\"\n",c);
#endif
system(c);
}
free(code);
if(ret==-1) break;
}
lirc_freeconfig(config);
}
lirc_deinit();
exit(EXIT_SUCCESS);
}
</PRE>
</P>
<P>
Before anything else you have to include the header file for the
lirc_client library. This is done with
<PRE>
#include &lt;lirc/lirc_client.h&gt;
</PRE>
Note that our example differs in this point because it was taken
directly from the lirc-0.6.0 source that comes with its own
<em>lirc_client.h</em> but we have to use the one that is already
installed on the system.
</P>
<P>
The next step is to initialize the library code with
<em>lirc_init()</em>. This function connects to lircd and does some
internal init stuff.
<PRE>
int lirc_init(char *prog,int verbose);
</PRE>
The first argument to this function is the string users will have to
provide as <em>prog</em> token in their .lircrc config files. If the
second argument is non-zero error messages will be printed to
<em>stderr</em>. Otherwise no error messages will ever be displayed.
This function returns the file descriptor of the socket that is
connected to lircd or -1 if an error occurred.
</P>
<P>
The example continues by reading a config file. This is done by the
<em>lirc_readconfig()</em> function:
<PRE>
int lirc_readconfig(char *file,struct lirc_config **config,
int (check)(char *s));
</PRE>
If you want to load the default config file you should pass NULL as
first argument. If you want to load some other config file the
<em>file</em> argument should contain the complete path to the
file. Your program should give the user the possibility to use an
other than the default config file. You should also be able to load
multiple config files by calling this function several times.<BR>
The <em>config</em> argument is used to pass the pointer to the config
file data structures back to your application. You will need it for
calls to the <em>lirc_code2char()</em> function. The last argument is
a call-back function that can be used to do syntax checks with the
config strings. The library code will call the call-back function for
all config strings where the <em>prog</em> token in the config file
matches the prog string you provided with the <em>lirc_init()</em>
function. If there is an error in the config string the call-back
function should return -1, otherwise 0. If you don't need to do any
syntax checks you can pass NULL here. The function returns -1 if an
error occurred, 0 otherwise.
</P>
<P>
The <em>lirc_nextcode()</em> function blocks until there is something
available on the lircd socket. This way it can be used in the main
loop of your program like in our example.
<PRE>
int lirc_nextcode(char **code);
</PRE>
If an error occurs (usually this means that the socket has been closed
by the daemon) this function returns -1. Otherwise it returns 0 and
<em>code</em> points to the next string available in the data
stream. This string has to be freed by your application using the
<em>free(3)</em> function. If no complete string is available
<em>code</em> will be NULL.<BR>
If you use some GUI-toolkit for your program then you probably won't
be able to use this function in your program's main loop because this
is already handled by the GUI-toolkit. In this situation you should
use the call-back abilities of the toolkit that will notify you
whenever there is some input available from a file descriptor (you get
the file descriptor from the <em>lirc_init()</em> function). E.g. you
can use the <em>gdk_input_add()</em>/<em>gdk_input_remove</em>()
functions with gtk or the <em>QSocketNotifier</em> class with Qt. If
you don't have such functionality in your toolkit or can't use it for
some reason you can still use SIGIO signals for this purpose. Check
the documentation for your GUI-toolkit and signal(2) for further
information.<BR>
Please note that using call-backs you still have to use some kind of
while loop to read strings from the socket because several strings may
be available in the data stream and you will only get a notification
for the first one. This poses a problem for us because
<em>lirc_nextcode()</em> blocks until there is something available
from the socket which is not what we need here. You can solve this
problem by setting the <b>O_NONBLOCK</b> flag for the socket using the
<em>fcntl(2)</em> function. Have a look at the current xirw code that
is available from the LIRC homepage for an implementation example.
</P>
<P>
To get the config string that the user has provided in the config file
in response to a button press you use the following function:
<PRE>
int lirc_code2char(struct lirc_config *config,char *code,char **string);
</PRE>
<em>config</em> is a pointer to the config file data structure that
you can get with <em>lirc_readconfig()</em> and <em>code</em> is the
code transmitted to your application on the lircd socket. If an action
should be taken <em>string</em> will point to the config string the
user has provided in the config file. The user might want to take
several actions on a button press so you have to execute this function
until <em>string</em> is NULL, which means that no more actions shall
be taken, or an error occurs. The function returns -1 if an error
occurred, 0 otherwise.
</P>
<P>
In our example there are only two clean-up functions to be explained.
<PRE>
void lirc_freeconfig(struct lirc_config *config);
</PRE>
This functions frees the data structures associated with <em>config</em>.
<PRE>
int lirc_deinit();
</PRE>
<em>lirc_deinit()</em> closes the connection to lircd and does some
internal clean-up stuff.
</P>
<P>
I encourage you to use autoconf and automake for your projects. To
check for the lirc_client library all you have to insert to your
<em>configure.in</em> file is the following:
<PRE>
dnl Check for LIRC client support
dnl This really is not worth making a separate file for it.
have_lirc=yes
AC_REQUIRE_CPP
AC_CHECK_LIB(lirc_client,lirc_init,
AC_CHECK_HEADER(lirc/lirc_client.h,true,have_lirc=no),have_lirc=no)
if test "$have_lirc" = "yes"; then
dnl AC_DEFINE(HAVE_LIRC);
true;
else
AC_MSG_ERROR([*** LIRC client support not available ***]);
fi
</PRE>
There is also a more complex m4 macro in the contrib directory of the
current LIRC distribution if you plan to add LIRC support to your
application without using the lirc_client library.
</P>
<A NAME="bugs"><HR></A>
<H1 ALIGN="CENTER">Known bugs</H1>
<HR WIDTH="70%">
<P>
If you use the <em>lirc_serial</em> or <em>lirc_parallel</em> 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 <em>netdate</em>
to synchronize your system clock regularly.
</P>

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