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<HTML><HEAD> <TITLE>RTAI 1.0 documentation - (new)FIFOs</TITLE> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"> <META NAME="Generator" CONTENT="VIM - Vi IMproved 5.3"></HEAD><BODY><A NAME="rtf_create"></A><dl><dt><H3>NAME</H3></dt><dd>rtf_create - create a real-time FIFO</dd></dl><dl><dt><H3>SYNOPSIS</H3></dt><dd>#include "rtai_fifos.h"<p><B>int rtf_create (unsigned int </B><I>fifo</I><B>, int </B><I>size</I><b>);</B></dd></dl><dl><dt><H3>DESCRIPTION</H3></dt><dd><b>rtf_create</b> creates a real-time fifo (RT-FIFO) of initial size <I>size</I>and assigns it the identifier <I>fifo</I>.<BR><I>fifo</I> is a small postive integer what identifies the fifo onfurther operations. It have to be less than RTF_NO.<br><i>fifo</i> may refer an existing RT-FIFO. In this case the size isadjusted if necessary.<p>The RT-FIFO is a mechanism, implemented as a characterdevice, to communicate between real-time tasks and ordinary Linux processes.The rtf_* functions are used by the real-time tasks; Linux processes usestandard character device access functions such as read, write, and select.</dd></dl><dl><dt><H3>RETURN VALUE</H3></dt><dd>On success, <I>size</I> is returned. On failure, a negativevalue is returned.</dd></dl><dl><dt><H3>ERRORS</H3></dt><dd> <dl><dt> -ENODEV </dt><dd> <I>fifo</I> is greater than or equal to RTF_NO. </dd></dl> <dl><dt> -ENOMEM </dt><dd> <I>size</I> bytes could not be allocated for the RT-FIFO. </dd></dl></dd></dl><dl><dt><H3>BUGS</H3></dt><dd>If resizing was unsuccesful, no error code is returned.</dd></dl><p align=right><A HREF="manual.html#fifo">[return to index]</A></p><HR ALIGN=LEFT SIZE=1 NOSHADE WIDTH="100%"><!-- -------------------------------------------------------- --><!--<A NAME="rtf_open_sized"></A><dl><dt><H3>NAME</H3></dt><dd>rtf_open_sized - open a real-time FIFO</dd></dl><dl><dt><H3>SYNOPSIS</H3></dt><dd>#include "rtai_fifos.h"<p><B>int rtf_open_sized (const char *</b><i>dev</i><b>, int </b><i>flags</i><b>, int </B><I>size</I><b>);</B></dd></dl><dl><dt><H3>DESCRIPTION</H3></dt><dd><p><b>rtf_open_sized</b> is called by Linux processes. It is a variantof the ordinary <b>open</b> system call. FIFOs opened by <b>open</b>has size DEFAULT_SIZE which is a compile time option. With<b>rtf_open_sized</b> the caller could set the FIFO size to any value.<br></dd></dl><dl><dt><H3>RETURN VALUE</H3></dt><dd><b>rtf_open_sized</b> returns the new file descriptor, or -1 if anerror occurred (in which case, errno is set appropriately).</dd></dl><dl><dt><H3>ERRORS</H3></dt><dd> See <b>open(2)</b>.</dd></dl><dl><dt><H3>BUGS</H3></dt><dd>If setting size to <i>size</i> is unsuccesful, no error code is returned.<p>At this moment <b>rtf_open_sized</b> does not work as expected.<br>Current code:<pre>static inline int rtf_open_sized(const char *dev, int perm, int size){ int fd; if ((fd = open(dev, perm)) < 0) { ioctl(fd, OPEN_SIZED, size); } return fd;}</pre></dd></dl><p align=right><A HREF="manual.html#fifo">[return to index]</A></p><HR ALIGN=LEFT SIZE=1 NOSHADE WIDTH="100%"><!-- -------------------------------------------------------- --><A NAME="rtf_destroy"></A><dl><dt><H3>NAME</H3></dt><dd>rtf_destroy - close a real-time FIFO</dd></dl><dl><dt><H3>SYNOPSIS</H3></dt><dd>#include "rtai_fifos.h"<p><B>int rtf_destroy (unsigned int </B><I>fifo</I><B>);</B></dd></dl><dl><dt><H3>DESCRIPTION</H3></dt><dd><b>rtf_destroy</b> closes a real-time fifo previously created/reopened with<b>rtf_create</b> or <b>rtf_open_sized</b>.An internal mechanism counts how many times a fifo was opened.Opens and closes must be in pair.<b>rtf_destroy</b> should be called as many times as <b>rtf_create</b>was. After the last close the fifo is really destroyed.</dd></dl><dl><dt><H3>RETURN VALUE</H3></dt><dd>On success, a non-negative number is returned. Actually it is theopen counter, that means how many times <b>rtf_destroy</b> shouldbe called yet to destroy the fifo.On failure, a negative value is returned.</dd></dl><dl><dt><H3>ERRORS</H3></dt><dd> <dl><dt> -ENODEV </dt><dd> <I>fifo</I> is greater than or equal to RTF_NO. </dd></dl> <dl><dt> -EINVAL </dt><dd> <I>fifo</I> refers to not an open fifo. </dd></dl></dd></dl><p align=right><A HREF="manual.html#fifo">[return to index]</A></p><HR ALIGN=LEFT SIZE=1 NOSHADE WIDTH="100%"><!-- -------------------------------------------------------- --><A NAME="rtf_reset"></A><dl><dt><H3>NAME</H3></dt><dd>rtf_reset - reset a real-time FIFO</dd></dl><dl><dt><H3>SYNOPSIS</H3></dt><dd>#include "rtai_fifos.h"<p><B>int rtf_reset (unsigned int </B><I>fifo</I><B>);</B></dd></dl><dl><dt><H3>DESCRIPTION</H3></dt><dd><b>rtf_reset</b> resets RT-FIFO <I>fifo</I> by setting its buffer pointersto zero, so that any existing data is discarded and the fifo started anewlike at its creations.</dd></dl><dl><dt><H3>RETURN VALUE</H3></dt><dd>On success, 0 is returned. On failure, a negativevalue is returned.</dd></dl><dl><dt><H3>ERRORS</H3></dt><dd> <dl><dt> -ENODEV </dt><dd> <I>fifo</I> is greater than or equal to RTF_NO. </dd></dl> <dl><dt> -EINVAL </dt><dd> <I>fifo</I> refers to not an open fifo. </dd></dl> <dl><dt> -EFAULT </dt><dd> Operation was unsuccesful. </dd></dl></dd></dl><p align=right><A HREF="manual.html#fifo">[return to index]</A></p><HR ALIGN=LEFT SIZE=1 NOSHADE WIDTH="100%"><!-- -------------------------------------------------------- --><A NAME="rtf_resize"></A><dl><dt><H3>NAME</H3></dt><dd>rtf_resize - resize a real-time FIFO</dd></dl><dl><dt><H3>SYNOPSIS</H3></dt><dd>#include "rtai_fifos.h"<p><B>int rtf_resize (unsigned int </B><I>fifo</I><B>, int </B><I>size</I><b>);</B></dd></dl><dl><dt><H3>DESCRIPTION</H3></dt><dd><b>rtf_resize</b> modifies the real-time fifo <I>fifo</I>, previouslycreated with , <b>rtf_create</b>, to have a new size of <I>size</I>.Any data in the fifo is discarded.</dd></dl><dl><dt><H3>RETURN VALUE</H3></dt><dd>On success, <I>size</I> is returned. On failure, a negativevalue is returned.</dd></dl><dl><dt><H3>ERRORS</H3></dt><dd> <dl><dt> -ENODEV </dt><dd> <I>fifo</I> is greater than or equal to RTF_NO. </dd></dl> <dl><dt> -EINVAL </dt><dd> <I>fifo</I> refers to not an open fifo. </dd></dl> <dl><dt> -ENOMEM </dt><dd> <I>size</I> bytes could not be allocated for the RT-FIFO. Fifo size is unchanged. </dd></dl></dd></dl><p align=right><A HREF="manual.html#fifo">[return to index]</A></p><HR ALIGN=LEFT SIZE=1 NOSHADE WIDTH="100%"><!-- -------------------------------------------------------- --><A NAME="rtf_put"></A><dl><dt><H3>NAME</H3></dt><dd>rtf_put - write data to FIFO</dd></dl><dl><dt><H3>SYNOPSIS</H3></dt><dd>#include "rtai_fifos.h"<p><B>int rtf_put (unsigned int </B><I>fifo</I><B>, void *</B><I>buf</I><B>, int </B><I>count</I><B>);</B></dd></dl><dl><dt><H3>DESCRIPTION</H3></dt><dd><b>rtf_put</b> tries to write a block of data to a real-time fifo previouslycreated with <b>rtf_create</b>.<BR><I>fifo</I> is the ID with which the RT-FIFO was created.<BR><I>buf</I> points the block of data to be written.<br><I>count</I> is the size of the block in bytes.<BR>This mechanism is available only to real-time tasks;Linux processes use a<code> write </code>to the corresponding<code> /dev/fifo<i><n></i> </code>device to enqueuedata to a fifo. Similarly, Linux processes use<code> read </code> or similar functionsto read the data previously written via <b>rtf_put</b>by a real-time task.</dd></dl><dl><dt><H3>RETURN VALUE</H3></dt><dd>On success, the number of bytes written is returned.Note that this value may be less than <I>count</I> if <I>count</I> bytesof free space is not available in the fifo.On failure, a negative value is returned.</dd></dl><dl><dt><H3>ERRORS</H3></dt><dd> <dl><dt> -ENODEV </dt><dd> <I>fifo</I> is greater than or equal to RTF_NO. </dd></dl> <dl><dt> -EINVAL </dt><dd> <I>fifo</I> refers to not an open fifo. </dd></dl></dd></dl><p align=right><A HREF="manual.html#fifo">[return to index]</A></p><HR ALIGN=LEFT SIZE=1 NOSHADE WIDTH="100%"><!-- -------------------------------------------------------- --><A NAME="rtf_get"></A><dl><dt><H3>NAME</H3></dt><dd>rtf_get - read data from FIFO</dd></dl><dl><dt><H3>SYNOPSIS</H3></dt><dd>#include "rtai_fifos.h"<p><B>int rtf_get (unsigned int </B><I>fifo</I><B>, void *</B><I>buf</I><B>, int </B><I>count</I><B>);</B></dd></dl><dl><dt><H3>DESCRIPTION</H3></dt><dd><b>rtf_get</b> tries to read a block of data from a real-time fifo previouslycreated with a call to <b>rtf_create</b>.<BR><I>fifo</I> is the ID with which the RT-FIFO was created.<BR><I>buf</I> points a buffer of <I>count</I> bytes size providedby the caller. Thismechanism is available only to real-time tasks; Linux processes use a<code> read </code>from the corresponding fifo device to dequeue data from a fifo.Similarly, Linux processes use<code> write </code>or similar functions towrite the data to be read via <b>rtf_put</b> by a real-time task.<p><b>rtf_get</b> is often used in conjunction with <b>rtf_create_handler</b>to process data received asynchronously from a Linux process. A handleris installed via <b>rtf_create_handler</b>;this handler calls <b>rtf_get</b> to receiveany data present in the RT-FIFO as it becomes available. In this way, pollingis not necessary; the handler is called only when data is present in thefifo.</dd></dl><dl><dt><H3>RETURN VALUE</H3></dt><dd>On success, the size of the received data block is returned.Note that this value may be less than <I>count</I> if <I>count</I> bytesof data is not available in the fifo.On failure, a negative value is returned.</dd></dl><dl><dt><H3>ERRORS</H3></dt><dd> <dl><dt> -ENODEV </dt><dd> <I>fifo</I> is greater than or equal to RTF_NO. </dd></dl> <dl><dt> -EINVAL </dt><dd> <I>fifo</I> refers to not an open fifo. </dd></dl></dd></dl><p align=right><A HREF="manual.html#fifo">[return to index]</A></p><HR ALIGN=LEFT SIZE=1 NOSHADE WIDTH="100%"><!-- -------------------------------------------------------- --><A NAME="rtf_create_handler"></A><dl><dt><H3>NAME</H3></dt><dd>rtf_create_handler - install a FIFO handler function</dd></dl><dl><dt><H3>SYNOPSIS</H3></dt><dd>#include "rtai_fifos.h"<p><B>int rtf_create_handler (unsigned int </B><I>fifo</I><B>, int (*</B><I>handler</I><B>)(unsigned int </B><I>fifo</I><B>));</B></dd></dl><dl><dt><H3>DESCRIPTION</H3></dt><dd><b>rtf_create_handler</b> installs a handler which is executed when datais written to or read from a real-time fifo.<BR><I>fifo</I> is an RT-FIFO that must have previously beencreated with a call to <B>rtf_create</B>.<BR>The function pointed by <I>handler</I> is called whenever a Linux processaccesses that fifo.<p><b>rtf_create_handler</b> is often used in conjunction with<b>rtf_get</b> to process data acquired asynchronouslyfrom a Linux process. The installed handler calls <b>rtf_get</b> when data ispresent. Because the handler is only executed when there is activity onthe fifo, polling is not necessary.</dd></dl><dl><dt><H3>RETURN VALUE</H3></dt><dd>On success, 0 is returned. On failure, a negative value isreturned.</dd></dl><dl><dt><H3>ERRORS</H3></dt><dd> <dl><dt> -EINVAL </dt><dd> <I>fifo</I> is greater than or equal to RTF_NO, or <I>handler</I> is NULL. </dd></dl></dd></dl><dl><dt><H3>BUGS</H3></dt><dd><b>rtf_create_handler</b> does not check if FIFO referred by <i>fifo</i>is open or not. The next call of <b>rtf_create</b> will uninstall the handlerjust "installed".</dd></dl><p align=right><A HREF="manual.html#fifo">[return to index]</A></p></BODY></HTML>⌨️ 快捷键说明
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