File: rtf_make_user_pair.3.html

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<HTML
><HEAD
><TITLE
>rtf_make_user_pair</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.64
"></HEAD
><BODY
CLASS="REFENTRY"
><H1
><A
NAME="AEN1"
>rtf_make_user_pair</A
></H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN5"
></A
><H2
>Name</H2
>rtf_make_user_pair&nbsp;--&nbsp;make a pair of RT-FIFOs act like a bidirectional FIFO</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN8"
></A
><H2
>Synopsis</H2
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="SYNOPSIS"
>       #include &#60;rtl_fifo.h&#62;

       int <TT
CLASS="FUNCTION"
>rtf_make_user_pair</TT
>(unsigned int <TT
CLASS="PARAMETER"
><I
>N</I
></TT
>, unsigned int <TT
CLASS="PARAMETER"
><I
>P</I
></TT
>);      </PRE
></TD
></TR
></TABLE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN13"
></A
><H2
>DESCRIPTION</H2
><P
>&#13;<TT
CLASS="FUNCTION"
>rtf_make_user_pair</TT
> modifies the behaviour of the RT-FIFO
<TT
CLASS="PARAMETER"
><I
>N</I
></TT
>: user-space reads of the
<TT
CLASS="PARAMETER"
><I
>/dev/rtfN</I
></TT
> are now routed to RT-FIFO
<TT
CLASS="PARAMETER"
><I
>P</I
></TT
>.  User-space writes to
<TT
CLASS="PARAMETER"
><I
>/dev/rtfN</I
></TT
> continue communicating with fifo
<TT
CLASS="PARAMETER"
><I
>N</I
></TT
>. This essentially makes
<TT
CLASS="PARAMETER"
><I
>/dev/rtfN</I
></TT
> bidirectional: data sent with
<TT
CLASS="FUNCTION"
>rtf_put</TT
> to FIFO <TT
CLASS="PARAMETER"
><I
>P</I
></TT
> will be read from
<TT
CLASS="PARAMETER"
><I
>/dev/rtfN</I
></TT
>; rtf_get on FIFO <TT
CLASS="PARAMETER"
><I
>N</I
></TT
> gets
data written to <TT
CLASS="PARAMETER"
><I
>/dev/rtfN</I
></TT
>.
RT-FIFO handlers are affected similarly.&#13;</P
><P
>The RT-FIFO is a mechanism, implemented as a character device, to communicate between realtime tasks and ordinary Linux processes.  The rtf_* functions are used by the realtime tasks;  Linux processes use standard character device access functions such as <TT
CLASS="FUNCTION"
>read(2)</TT
>, <TT
CLASS="FUNCTION"
>write(2</TT
>) and <TT
CLASS="FUNCTION"
>select(2)</TT
>.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN32"
></A
><H2
>RETURN VALUE</H2
><P
>This function returns 0 on success and a negative error code on error.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN35"
></A
><H2
>ERRORS</H2
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>-ENODEV</DT
><DD
><P
><TT
CLASS="PARAMETER"
><I
>N</I
></TT
> or <TT
CLASS="PARAMETER"
><I
>P</I
></TT
> is greater than or equal to RTF_NO.</P
></DD
><DT
>-EINVAL</DT
><DD
><P
><TT
CLASS="PARAMETER"
><I
>N</I
></TT
> or <TT
CLASS="PARAMETER"
><I
>P</I
></TT
> is not a valid RT-FIFO identifier.</P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN50"
></A
><H2
>NOTES</H2
><P
>This function is useful when implementing Linux character device drivers on
top of RT-FIFOs.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN53"
></A
><H2
>SEE ALSO</H2
><A
HREF="../susv2/xns/read.html"
TARGET="_top"
>read(2)</A
>, <A
HREF="rtf_create.3.html"
TARGET="_top"
>rtf_create(3)</A
>, <A
HREF="rtf_create_handler.3.html"
TARGET="_top"
>rtf_create_handler(3)</A
>, <A
HREF="rtf_destroy.3.html"
TARGET="_top"
>rtf_destroy(3)</A
>, <A
HREF="rtf_get.3.html"
TARGET="_top"
>rtf_get(3)</A
>, <A
HREF="rtf_link_user_ioctl.3.html"
TARGET="_top"
>rtf_link_user_ioctl(3)</A
>, <A
HREF="../susv2/xns/write.html"
TARGET="_top"
>write(2)</A
><P
>2001 FSMLabs Inc.</P
><P
>All rights reserved.</P
></DIV
></BODY
></HTML
>