03.char/03.char.xml

   1 <?xml version="1.0" encoding="UTF-8" ?>
   2 <!DOCTYPE slides SYSTEM "/usr/share/xml/docbook/custom/slides/3.3.1/schema/dtd/slides-full.dtd">
   3
   4 <slides>
   5
   6 <slidesinfo>
   7 <title>Character Devices</title>
   8 <author><firstname>Thadeu</firstname><surname>Cascardo</surname></author>
   9 </slidesinfo>
  10
  11 <foil>
  12 <title>Introduction</title>
  13 </foil>
  14
  15 <foil>
  16 <title>Device Number Macros</title>
  17 <para>
  18 Nowadays, major number is 12 bits and minor number is 20 bits. This may change
  19 in the future, so macros should be used.
  20 </para>
  21 <itemizedlist>
  22 <listitem>
  23 MAJOR
  24 </listitem>
  25 <listitem>
  26 MINOR
  27 </listitem>
  28 <listitem>
  29 MKDEV
  30 </listitem>
  31 </itemizedlist>
  32 </foil>
  33
  34 <foil>
  35 <title>Allocating numbers</title>
  36 <para>
  37 Use <emphasis>register\_chrdev\_region</emphasis> or
  38 <emphasis>alloc\_chrdev\_region</emphasis> to register or allocate device
  39 numbers.
  40 </para>
  41 <para>
  42 Use <emphasis>unregister\_chrdev\_region</emphasis> to unregister it.
  43 </para>
  44 </foil>
  45
  46 <foil>
  47 <title>cdev structure</title>
  48 <para>
  49 Use <emphasis>cdev\_alloc</emphasis> or <emphasis>cdev\_init</emphasis> to
  50 allocate or initalize a cdev structure.
  51 </para>
  52 <para>
  53 Use <emphasis>cdev\_add</emphasis> and <emphasis>cdev\_del</emphasis> to
  54 register and unregister it.
  55 </para>
  56 </foil>
  57
  58 <foil>
  59 <title>Open/Release</title>
  60 <para>
  61 Implementing open and release should be very simple for many devices. They
  62 usually allocate data, and multiplex devices by minor number.
  63 </para>
  64 </foil>
  65
  66 <foil>
  67 <title>Inode structure</title>
  68 <para>
  69 Use <emphasis>imajor</emphasis> and <emphasis>iminor</emphasis> to get the major
  70 and minor number from an inode structure.
  71 </para>
  72 </foil>
  73
  74 <foil>
  75 <title>Read</title>
  76 <para>
  77 Read may write to user space less bytes than requested.
  78 </para>
  79 </foil>
  80
  81 <foil>
  82 <title>Write</title>
  83 <para>
  84 Write is very similar to read. Only problem is that many applications misbehave
  85 when driver writes less bytes than requested.
  86 </para>
  87 </foil>
  88
  89 </slides>