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📁 What is this ``device driver stuff anyway? Here s a very short introduction to the concept.
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<html><head><title>Data Structures That the Autoconfiguration Software Uses</title>

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<meta name="DESCRIPTION" content="Writing Device Drivers Tutorial: DIGITAL UNIX Version 4.0B documentation set">
<meta name="AUTHOR" content="Copyright (c) Digital Equipment Corporation 1996. All Rights Reserved."></head>
<body>
<a name="DeviceAutoconfig"></a>
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</p><h1>17&nbsp;&nbsp;&nbsp;&nbsp;Data Structures That the Autoconfiguration Software Uses</h1>
<p>
<a name="nx_id_703"></a>
Autoconfiguration is a process that determines what hardware actually
exists during the current instance of the running kernel at static
configuration time.
<a name="nx_id_704"></a>
The autoconfiguration software creates
a configuration tree that represents the current system configuration.
In creating this configuration tree, the autoconfiguration software uses
the following data structures:
</p><ul>
<p></p><li>
<tt>bus</tt>
<p></p></li><li>
<tt>controller</tt>
<p></p></li><li>
<tt>device</tt>
<p></p></li><li>
<tt>driver</tt>
<p></p></li><li>
<tt>port</tt>
</li></ul><p>
The following sections describe each of these data structures except the
<tt>driver</tt>
structure.
<a href="http://h30097.www3.hp.com/docs/base_doc/DOCUMENTATION/HTML/AA-PUBVD-TE_html/drivertut8.html#driver_struct">Section 5.3</a>
describes the
<tt>driver</tt>
structure.
<a name="BusStruct"></a>
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</p><h2>
17.1&nbsp;&nbsp;&nbsp;&nbsp;The bus Structure
</h2>
<p>
The
<tt>bus</tt>
structure represents an instance of a bus entity.
A bus is a real or imagined entity to which other buses or
controllers are logically attached.
All systems have at least one bus, the system bus, even though the bus
may not actually exist physically.
The term
<em>controller</em>
here refers both to devices that control slave
devices (for example, disk or tape controllers) and to devices that
stand alone (for example, terminal or network controllers).
Bus adapter driver writers create
<tt>bus</tt>
structures by calling the
<tt>create_bus_struct</tt>
interface and passing to it a filled-in
<tt>bus_config</tt>
structure.
The discussion of how to use the
<tt>create_bus_struct</tt>
interface and how to fill in the
<tt>bus_config</tt>
structure is beyond the scope of this book.
However, the descriptions of the
<tt>bus</tt>
structure are presented here.
</p><p>
<a href="http://h30097.www3.hp.com/docs/base_doc/DOCUMENTATION/HTML/AA-PUBVD-TE_html/drivertut24.html#TblBusStructMembers">Table 17-1</a>
lists the members of the
<tt>bus</tt>
structure along with their associated data types.
</p><p>
<a name="TblBusStructMembers"></a>
</p><h3>
Table 17-1: Members of the bus Structure
</h3>
<a name="nx_id_705"></a>
<table border="4" cellpadding="4">
<tbody><tr>
<td align="left" valign="top">
<strong>
Member Name
</strong>
</td>
<td align="left" valign="top">
<strong>
Data Type
</strong>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>bus_mbox</tt>
</td>
<td align="left" valign="top">
<tt>u_long *</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>bus_hd</tt>
</td>
<td align="left" valign="top">
<tt>struct bus *</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>nxt_bus</tt>
</td>
<td align="left" valign="top">
<tt>struct bus *</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>ctlr_list</tt>
</td>
<td align="left" valign="top">
<tt>struct controller *</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>bus_list</tt>
</td>
<td align="left" valign="top">
<tt>struct bus *</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>bus_type</tt>
</td>
<td align="left" valign="top">
<tt>int</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>bus_name</tt>
</td>
<td align="left" valign="top">
<tt>char *</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>bus_num</tt>
</td>
<td align="left" valign="top">
<tt>int</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>slot</tt>
</td>
<td align="left" valign="top">
<tt>int</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>connect_bus</tt>
</td>
<td align="left" valign="top">
<tt>char *</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>connect_num</tt>
</td>
<td align="left" valign="top">
<tt>int</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>confl1</tt>
</td>
<td align="left" valign="top">
<tt>int (*confl1)()</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>confl2</tt>
</td>
<td align="left" valign="top">
<tt>int (*confl2)()</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>pname</tt>
</td>
<td align="left" valign="top">
<tt>char *</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>port</tt>
</td>
<td align="left" valign="top">
<tt>struct port *</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>intr</tt>
</td>
<td align="left" valign="top">
<tt>int (**intr)()</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>alive</tt>
</td>
<td align="left" valign="top">
<tt>int</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>framework</tt>
</td>
<td align="left" valign="top">
<tt>struct bus_framework *</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>driver_name</tt>
</td>
<td align="left" valign="top">
<tt>char *</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>bus_bridge_dma</tt>
</td>
<td align="left" valign="top">
<tt>void *</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>private</tt>
</td>
<td align="left" valign="top">
<tt>void * [8]</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>conn_priv</tt>
</td>
<td align="left" valign="top">
<tt>void * [8]</tt>
</td>
</tr>
<tr>
<td align="left" valign="top">
<tt>rsvd</tt>
</td>
<td align="left" valign="top">
<tt>void * [7]</tt>
</td>
</tr>
</tbody></table><p>
</p><p>
The following sections discuss all of these members.
<a name="busmbox"></a>
</p><p></p><hr><p align="center">
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</p><p></p><hr><p>
</p><h3>
17.1.1&nbsp;&nbsp;&nbsp;&nbsp;The bus_mbox Member
</h3>
<p>
The
<tt>bus_mbox</tt>
member specifies
a pointer to the mailbox data structure for hardware platforms that
access I/O space through hardware mailboxes.
The bus adapter code sets this member.
As the adapter code probes the buses, the first bus that has a mailbox
allocates the initial software mailbox data structure and sets its
<tt>bus_mbox</tt>
pointer to that data structure.
As the adapter code continues to probe for buses and controllers,
the
<tt>MBOX_GET</tt>
macro allocates the
<tt>ctlr_mbox</tt>
members for devices accessed by mailboxes.
Typically, this macro is called in the controller configuration
interface after the
<tt>controller</tt>
data structure has been found, but before probing the controller.
The following code fragment gives an idea of the tasks that occur prior
to calling the
<tt>MBOX_GET</tt>
macro:
</p><p>
</p><p>
</p><pre>config_con(name, node, bus)
{
   register struct controller *ctlr;

   if((ctlr = get_ctlr(name, node, bus-&gt;bus_name, bus-&gt;bus_num)) ||
          /* other wildcards here */
      (ctlr = get_ctlr(name, -1, "*", -99))) {
<br>.<br>.<br>.<br>
       }

/***************************************************
 * Found the controller                            *
 ***************************************************/

           int savebusnum;
           char *savebusname;
           int saveslot;
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