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  <header>
    <copyright>
      <year>2013</year><year>2014</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
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    </legalnotice>

    <title>erl_driver for Enea OSE</title>
    <prepared>Lukas Larsson</prepared>
    <docno></docno>
    <date>2014-01-08</date>
    <rev>A</rev>
    <file>ose_erl_driver.xml</file>
  </header>
  <lib>ose_erl_driver</lib>
  <libsummary>Linked-in drivers in Enea OSE</libsummary>
  <description>
    <p>Writing Linked-in drivers that also work on Enea OSE is very similar for
    how you would do it for Unix. The difference from Unix is that
    driver_select, ready_input and ready_output all work with signals
    instead of file descriptors. This means that the driver_select is
    used to specify which type of signal should trigger calls to
    ready_input/ready_output. The functions described below are available
    to driver programmers on Enea OSE to facilitate this.
    </p>
  </description>
  <section>
    <title>DATA TYPES</title>

    <taglist>
      <tag><marker id="union_SIGNAL"/>union SIGNAL</tag>
      <item>See the Enea OSE SPI documentation for a description.</item>
      <tag><marker id="SIGSELECT"/>SIGSELECT</tag>
      <item>See the Enea OSE SPI documentation for a description.</item>
      <tag><marker id="ErlDrvEvent"/>ErlDrvEvent</tag>
      <item>The <c>ErlDrvEvent</c> is a handle to a signal number and id combination. It is passed to <seealso marker="erts:erl_driver#driver_select">driver_select(3)</seealso>.</item>
      <tag><marker id="ErlDrvOseEventId"/>ErlDrvOseEventId</tag>
      <item>This is the id used to associate a specific signal to a
      certain driver instance. </item>
    </taglist>
  </section>
  <funcs>
    <func>
      <name><ret>union SIGNAL *</ret><nametext>erl_drv_ose_get_signal(ErlDrvEvent drv_event)</nametext></name>
      <desc>
        <marker id="erl_drv_ose_get_signal"></marker>
        <p>Fetch the next signal associated with <c>drv_event</c>.
	Signals will be returned in the order which they were received and
	when no more signals are available <c>NULL</c> will be returned.
	Use this function in the ready_input/ready_output callbacks
	to get signals.</p>
      </desc>
    </func>
    <func>
      <name><ret>ErlDrvEvent</ret><nametext>erl_drv_ose_event_alloc(SIGSELECT signo, ErlDrvOseEventId id, ErlDrvOseEventId (*resolve_signal)(union SIGNAL* sig), void *extra)</nametext></name>
      <desc>
        <marker id="erl_drv_ose_event_alloc"></marker>
        <p>Create a new <c>ErlDrvEvent</c> associated with <c>signo</c>,
	<c>id</c> and uses the <c>resolve_signal</c> function to extract
	the <c>id</c> from a signal with <c>signo</c>. The <c>extra</c>
	parameter can be used for additional data. See
	<seealso marker="ose_signals_chapter#driver">
	Signals in a Linked-in driver</seealso> in the OSE User's Guide.
      </p>
      </desc>
    </func>
    <func>
      <name><ret>void</ret><nametext>erl_drv_ose_event_free(ErlDrvEvent drv_event)</nametext></name>
      <desc>
        <marker id="erl_drv_ose_event_free"></marker>
        <p>Free a <c>ErlDrvEvent</c>. This should always be done in the
	<seealso marker="erts:driver_entry#stop_select">stop_select</seealso>
	callback when the event is no longer being used.</p>
      </desc>
    </func>
    <func>
      <name><ret>void</ret><nametext>erl_drv_ose_event_fetch(ErlDrvEvent drv_event, SIGSELECT *signo, ErlDrvOseEventId *id, void **extra)</nametext></name>
      <desc>
        <marker id="erl_drv_ose_event_fetch"></marker>
        <p>Write the signal number, id and any extra data associated with <c>drv_event</c>
	into <c>*signo</c> and <c>*id</c> respectively. <c>NULL</c> can be
	also passed as <c>signo</c> or <c>id</c> in order to ignore that field.
	</p>
      </desc>
    </func>
  </funcs>
  <section>
    <title>SEE ALSO</title>
    <p>
      <seealso marker="erts:driver_entry">driver_entry(3)</seealso>,
      <seealso marker="erts:erl_driver">erl_driver(3)</seealso>
    </p>
  </section>
</cref>
