docs/egl.html

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   9 <h1>Mesa EGL</h1>
  10
  11 <p>The current version of EGL in Mesa implements EGL 1.4.  More information
  12 about EGL can be found at
  13 <a href="http://www.khronos.org/egl/" target="_parent">
  14 http://www.khronos.org/egl/</a>.</p>
  15
  16 <p>The Mesa's implementation of EGL uses a driver architecture.  The main
  17 library (<code>libEGL</code>) is window system neutral.  It provides the EGL
  18 API entry points and helper functions for use by the drivers.  Drivers are
  19 dynamically loaded by the main library and most of the EGL API calls are
  20 directly dispatched to the drivers.</p>
  21
  22 <p>The driver in use decides the window system to support.  For drivers that
  23 support hardware rendering, there are usually multiple drivers supporting the
  24 same window system.  Each one of of them supports a certain range of graphics
  25 cards.</p>
  26
  27 <h2>Build EGL</h2>
  28
  29 <ol>
  30 <li>
  31 <p>Run <code>configure</code> with the desired state trackers and and enable
  32 the Gallium driver for your hardware.  For example</p>
  33
  34 <pre>
  35   $ ./configure --with-state-trackers=egl,es,vega --enable-gallium-intel
  36 </pre>
  37
  38 <p>The main library will be enabled by default.  The <code>egl</code> state
  39 tracker is needed by a number of EGL drivers.  EGL drivers will be covered
  40 later.  The <a href="opengles.html">es state tracker</a> provides OpenGL ES 1.x
  41 and 2.x and the <a href="openvg.html">vega state tracker</a> provides OpenVG
  42 1.x.</p>
  43 </li>
  44
  45 <li>Build and install Mesa as usual.</li>
  46 </ol>
  47
  48 <p>In the given example, it will build and install <code>libEGL</code>,
  49 <code>libGLESv1_CM</code>, <code>libGLESv2</code>, <code>libOpenVG</code>, and
  50 one or more EGL drivers.</p>
  51
  52 <h3>Configure Options</h3>
  53
  54 <p>There are several options that control the build of EGL at configuration
  55 time</p>
  56
  57 <ul>
  58 <li><code>--enable-egl</code>
  59
  60 <p>By default, EGL is enabled.  When disabled, the main library and the drivers
  61 will not be built.</p>
  62
  63 </li>
  64
  65 <li><code>--with-egl-displays</code>
  66
  67 <p>List the window system(s) to support.  It is by default <code>x11</code>,
  68 which supports the X Window System.  Its argument is a comma separated string
  69 like, for example, <code>--with-egl-displays=x11,kms</code>.  Because an EGL
  70 driver decides which window system to support, this example will enable two
  71 (sets of) EGL drivers.  One supports the X window system and the other supports
  72 bare KMS (kernel modesetting).</p>
  73
  74 </li>
  75
  76 <li><code>--with-state-trackers</code>
  77
  78 <p>The argument is a comma separated string.  It is usually used to specify the
  79 rendering APIs, like OpenGL ES or OpenVG, to build.  But it should be noted
  80 that a number of EGL drivers depend on the <code>egl</code> state tracker.
  81 They will <em>not</em> be built without the <code>egl</code> state tracker.</p>
  82
  83 </li>
  84
  85 <li><code>--enable-gallium-swrast</code>
  86
  87 <p>This option is not specific to EGL.  But if there is no driver for your
  88 hardware, or you are experiencing problems with the hardware driver, you can
  89 enable the swrast DRM driver.  It is a dummy driver and EGL will fallback to
  90 software rendering automatically.</p>
  91
  92 </li>
  93 </ul>
  94
  95 <h3>OpenGL</h3>
  96
  97 <p>The OpenGL state tracker is not built in the above example.  It should be
  98 noted that the classic <code>libGL</code> is not a state tracker and cannot be
  99 used with EGL (unless the EGL driver in use is <code>egl_glx</code>).  To build
 100 the OpenGL state tracker, one may append <code>glx</code> to
 101 <code>--with-state-trackers</code> and manually build
 102 <code>src/gallium/winsys/xlib/</code>.</p>
 103
 104 <h2>Use EGL</h2>
 105
 106 <p> The demos for OpenGL ES and OpenVG can be found in <code>progs/es1/</code>,
 107 <code>progs/es2/</code> and <code>progs/openvg/</code>.  You can use them to
 108 test your build.  For example,</p>
 109
 110 <pre>
 111   $ cd progs/es1/xegl
 112   $ make
 113   $ ./torus
 114 </pre>
 115
 116 <h3>Environment Variables</h3>
 117
 118 <p>There are several environment variables that control the behavior of EGL at
 119 runtime</p>
 120
 121 <ul>
 122 <li><code>EGL_DRIVER</code>
 123
 124 <p>This variable forces the specified EGL driver to be loaded.  It comes in
 125 handy when one wants to test a specific driver.</p>
 126
 127 </li>
 128
 129 <li><code>EGL_DISPLAY</code>
 130
 131 <p>When <code>EGL_DRIVER</code> is not set, the main library loads <em>all</em>
 132 EGL drivers that support a certain window system.  <code>EGL_DISPLAY</code> can
 133 be used to specify the window system and the valid values are, for example,
 134 <code>x11</code> or <code>kms</code>.  When the variable is not set, the main
 135 library defaults the value to the first window system listed in
 136 <code>--with-egl-displays</code> at configuration time.
 137
 138 </li>
 139
 140 <li><code>EGL_LOG_LEVEL</code>
 141
 142 <p>This changes the log level of the main library and the drivers.  The valid
 143 values are: <code>debug</code>, <code>info</code>, <code>warning</code>, and
 144 <code>fatal</code>.</p>
 145
 146 </li>
 147
 148 <li><code>EGL_SOFTWARE</code>
 149
 150 <p>For drivers that support both hardware and software rendering, setting this
 151 variable to true forces the use of software rendering.</p>
 152
 153 </li>
 154 </ul>
 155
 156 <h2>EGL Drivers</h2>
 157
 158 <p>There are two categories of EGL drivers: Gallium and classic.</p>
 159
 160 <p>Gallium EGL drivers supports all rendering APIs specified in EGL 1.4.  The
 161 support for optional EGL functions and EGL extensions is usually more complete
 162 than the classic ones.  These drivers depend on the <code>egl</code> state
 163 tracker to build.  The available drivers are</p>
 164
 165 <ul>
 166 <li><code>egl_&lt;dpy&gt;_i915</code></li>
 167 <li><code>egl_&lt;dpy&gt;_i965</code></li>
 168 <li><code>egl_&lt;dpy&gt;_radeon</code></li>
 169 <li><code>egl_&lt;dpy&gt;_nouveau</code></li>
 170 <li><code>egl_&lt;dpy&gt;_swrast</code></li>
 171 <li><code>egl_&lt;dpy&gt;_vmwgfx</code></li>
 172 </ul>
 173
 174 <p><code>&lt;dpy&gt;</code> is given by <code>--with-egl-displays</code> at
 175 configuration time.  There will be one EGL driver for each combination of the
 176 displays listed and the hardware drivers enabled.</p>
 177
 178 <p>Classic EGL drivers, on the other hand, supports only OpenGL as its
 179 rendering API.  They can be found under <code>src/egl/drivers/</code>.  There
 180 are 3 of them</p>
 181
 182 <ul>
 183 <li><code>egl_glx</code>
 184
 185 <p>This driver provides a wrapper to GLX.  It uses exclusively GLX to implement
 186 the EGL API.  It supports both direct and indirect rendering when the GLX does.
 187 It is accelerated when the GLX is.  As such, it cannot provide functions that
 188 is not available in GLX or GLX extensions.</p>
 189 </li>
 190
 191 <li><code>egl_xdri</code>
 192
 193 <p>This driver supports the X Window System as its window system.  It functions
 194 as a DRI driver loader and can load DRI/DRI2/DRISW drivers.  Unlike
 195 <code>egl_glx</code>, it has no dependency on <code>libGL</code>.  It talks to
 196 the X server directly using DRI or DRI2 protocols.  It also talks minimal GLX
 197 protocol for things like available visuals or fbconfigs.  With direct access to
 198 the DRI drivers, it has the potential to support more EGL functions that are
 199 not possible with <code>egl_glx</code>.</p>
 200
 201 </li>
 202 <li><code>egl_dri</code>
 203
 204 <p>This driver lacks maintenance and does <em>not</em> build.  It is similiar
 205 to <code>egl_xdri</code> in that it functions as a DRI driver loader.  But
 206 unlike <code>egl_xdri</code>, it supports Linux framebuffer devices as its
 207 window system and supports EGL_MESA_screen_surface extension.  It loads only
 208 DRI1 drivers.  As DRI1 drivers is phasing out, it might be better to rewrite
 209 the driver to support KMS and DRI2.</p>
 210
 211 </li>
 212 </ul>
 213
 214 <p>To use the classic drivers, one must manually set <code>EGL_DRIVER</code> at
 215 runtime.</p>
 216
 217 <h2>Developers</h2>
 218
 219 The sources of the main library and the classic drivers can be found at
 220 <code>src/egl/</code>.  The sources of the <code>egl</code> state tracker can
 221 be found at <code>src/gallium/state_trackers/egl/</code>.
 222
 223 <h3>TODOs</h3>
 224
 225 <ul>
 226 <li>Thread safety</li>
 227 <li>Pass the conformance tests</li>
 228 <li>Better automatic driver selection: <code>EGL_DISPLAY</code> loads all
 229 drivers and might eat too much memory.</li>
 230
 231 </ul>
 232
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