Mesa EGL
The current version of EGL in Mesa implements EGL 1.4. More information about EGL can be found at - + http://www.khronos.org/egl/.
The Mesa's implementation of EGL uses a driver architecture. The main @@ -19,114 +27,122 @@ API entry points and helper functions for use by the drivers. Drivers are dynamically loaded by the main library and most of the EGL API calls are directly dispatched to the drivers.
-The driver in use decides the window system to support. For drivers that -support hardware rendering, there are usually multiple drivers supporting the -same window system. Each one of of them supports a certain range of graphics -cards.
+The driver in use decides the window system to support.
Build EGL
-
-
Run
+configure
with the desired state trackers and enable -the Gallium driver for your hardware. For exampleRun
configure
with the desired client APIs and enable +the driver for your hardware. For example- $ ./configure --with-state-trackers=egl,es,vega --enable-gallium-{swrast,intel} + $ ./configure --enable-gles1 --enable-gles2 \ + --with-dri-drivers=... \ + --with-gallium-drivers=...
-The main library will be enabled by default. The
+egl
state -tracker is needed by a number of EGL drivers. EGL drivers will be covered -later. The es state tracker provides OpenGL ES 1.x -and 2.x and the vega state tracker provides OpenVG -1.x.The main library and OpenGL is enabled by default. The first two options +above enables OpenGL ES 1.x and 2.x. The last two +options enables the listed classic and and Gallium drivers respectively.
+ - Build and install Mesa as usual.
In the given example, it will build and install libEGL
,
-libGLESv1_CM
, libGLESv2
, libOpenVG
, and
-one or more EGL drivers.
libGL
, libGLESv1_CM
, libGLESv2
, and one
+or more EGL drivers.
Configure Options
There are several options that control the build of EGL at configuration time
--
-
--enable-egl
+-
+
--enable-egl
+-
By default, EGL is enabled. When disabled, the main library and the drivers will not be built.
-
+
---with-egl-driver-dir
+ +--with-egl-driver-dir
The directory EGL drivers should be installed to. If not specified, EGL drivers will be installed to
-${libdir}/egl
.
+
---with-egl-displays
+ +--enable-gallium-egl
- -
List the window system(s) to support. It is by default
+x11
, -which supports the X Window System. Its argument is a comma separated string -like, for example,--with-egl-displays=x11,kms
. Because an EGL -driver decides which window system to support, this example will enable two -(sets of) EGL drivers. One supports the X window system and the other supports -bare KMS (kernel modesetting).Enable the optional
-egl_gallium
driver.
+
---with-state-trackers
+ +--with-egl-platforms
- -
The argument is a comma separated string. It is usually used to specify the -rendering APIs, like OpenGL ES or OpenVG, to build. But it should be noted -that a number of EGL drivers depend on the
+egl
state tracker. -They will not be built without theegl
state tracker.List the platforms (window systems) to support. Its argument is a comma +separated string such as
---with-egl-platforms=x11,drm
. It decides +the platforms a driver may support. The first listed platform is also used by +the main library to decide the native platform: the platform the EGL native +types such asEGLNativeDisplayType
or +EGLNativeWindowType
defined for.
+--enable-gallium-swrast
+ -This option is not specific to EGL. But if there is no driver for your -hardware, or you are experiencing problems with the hardware driver, you can -enable the swrast DRM driver. It is a dummy driver and EGL will fallback to -software rendering automatically.
+ +--enable-gles1
+--enable-gles2
- -
-
The available platforms are x11
, drm
,
+fbdev
, and gdi
. The gdi
platform can
+only be built with SCons. Unless for special needs, the build system should
+select the right platforms automatically.
These options enable OpenGL ES support in OpenGL. The result is one big +internal library that supports multiple APIs.
+ + -OpenGL
+--enable-shared-glapi
The OpenGL state tracker is not built in the above example. It should be
-noted that the classic libGL
is not a state tracker and cannot be
-used with EGL (unless the EGL driver in use is egl_glx
). To build
-the OpenGL state tracker, one may append glx
to
---with-state-trackers
and manually build
-src/gallium/winsys/xlib/
.
By default, libGL
has its own copy of libglapi
.
+This options makes libGL
use the shared libglapi
. This
+is required if applications mix OpenGL and OpenGL ES.
--enable-openvg
OpenVG must be explicitly enabled by this option.
+ +Use EGL
- The demos for OpenGL ES and OpenVG can be found in progs/es1/
,
-progs/es2/
and progs/openvg/
. You can use them to
-test your build. For example,
Demos
-- $ cd progs/es1/xegl - $ make - $ ./torus -+
There are demos for the client APIs supported by EGL. They can be found in +mesa/demos repository.
Environment Variables
There are several environment variables that control the behavior of EGL at runtime
--
-
EGL_DRIVERS_PATH
+-
+
EGL_DRIVERS_PATH
+-
By default, the main library will look for drivers in the directory where the drivers are installed to. This variable specifies a list of @@ -134,98 +150,101 @@ colon-separated directories where the main library will look for drivers, in addition to the default directory. This variable is ignored for setuid/setgid binaries.
-
+
This variable is usually set to test an uninstalled build. For example, one +may set
+ ++ $ export LD_LIBRARY_PATH=$mesa/lib + $ export EGL_DRIVERS_PATH=$mesa/lib/egl +-
EGL_DRIVER
+to test a build without installation
-This variable specifies a full path to an EGL driver and it forces the -specified EGL driver to be loaded. It comes in handy when one wants to test a -specific driver. This variable is ignored for setuid/setgid binaries.
+ -EGL_DRIVER
EGL_DISPLAY
+This variable specifies a full path to or the name of an EGL driver. It +forces the specified EGL driver to be loaded. It comes in handy when one wants +to test a specific driver. This variable is ignored for setuid/setgid +binaries.
-When EGL_DRIVER
is not set, the main library loads all
-EGL drivers that support a certain window system. EGL_DISPLAY
can
-be used to specify the window system and the valid values are, for example,
-x11
or kms
. When the variable is not set, the main
-library defaults the value to the first window system listed in
---with-egl-displays
at configuration time.
+
EGL_PLATFORM
This variable specifies the native platform. The valid values are the same
+as those for --with-egl-platforms
. When the variable is not set,
+the main library uses the first platform listed in
+--with-egl-platforms
as the native platform.
EGL_LOG_LEVEL
+Extensions like EGL_MESA_drm_display
define new functions to
+create displays for non-native platforms. These extensions are usually used by
+applications that support non-native platforms. Setting this variable is
+probably required only for some of the demos found in mesa/demo repository.
EGL_LOG_LEVEL
This changes the log level of the main library and the drivers. The valid
values are: debug
, info
, warning
, and
fatal
.
EGL_SOFTWARE
+EGL_SOFTWARE
For drivers that support both hardware and software rendering, setting this variable to true forces the use of software rendering.
-EGL Drivers
-There are two categories of EGL drivers: Gallium and classic.
- -Gallium EGL drivers supports all rendering APIs specified in EGL 1.4. The
-support for optional EGL functions and EGL extensions is usually more complete
-than the classic ones. These drivers depend on the egl
state
-tracker to build. The available drivers are
-
-
egl_<dpy>_i915
-egl_<dpy>_i965
-egl_<dpy>_radeon
-egl_<dpy>_nouveau
-egl_<dpy>_swrast
-egl_<dpy>_vmwgfx
-
<dpy>
is given by --with-egl-displays
at
-configuration time. There will be one EGL driver for each combination of the
-displays listed and the hardware drivers enabled.
Classic EGL drivers, on the other hand, supports only OpenGL as its
-rendering API. They can be found under src/egl/drivers/
. There
-are 3 of them
-
-
egl_glx
- -This driver provides a wrapper to GLX. It uses exclusively GLX to implement -the EGL API. It supports both direct and indirect rendering when the GLX does. -It is accelerated when the GLX is. As such, it cannot provide functions that -is not available in GLX or GLX extensions.
-
+egl_dri2
+-
-
-egl_dri2
+This driver supports both
-x11
anddrm
platforms. +It functions as a DRI driver loader. Forx11
support, it talks to +the X server directly using (XCB-)DRI2 protocol.This driver supports the X Window System as its window system. It functions -as a DRI2 driver loader. Unlike
+egl_glx
, it has no dependency on -libGL
. It talks to the X server directly using DRI2 protocol.This driver can share DRI drivers with
-libGL
.egl_dri
+
- egl_gallium
+- - -
-
+
This driver lacks maintenance and does not build. It is similiar
-to egl_dri2
in that it functions as a DRI(1) driver loader. But
-unlike egl_dri2
, it supports Linux framebuffer devices as its
-window system and supports EGL_MESA_screen_surface extension. As DRI1 drivers
-are phasing out, it might eventually be replaced by egl_dri2
.
This driver is based on Gallium3D. It supports all rendering APIs and +hardware supported by Gallium3D. It is the only driver that supports OpenVG. +The supported platforms are X11, DRM, FBDEV, and GDI.
+ +This driver comes with its own hardware drivers
+(pipe_<hw>
) and client API modules
+(st_<api>
).
Packaging
-To use the classic drivers, one must manually set EGL_DRIVER
at
-runtime.
The ABI between the main library and its drivers are not stable. Nor is
+there a plan to stabilize it at the moment. Of the EGL drivers,
+egl_gallium
has its own hardware drivers and client API modules.
+They are considered internal to egl_gallium
and there is also no
+stable ABI between them. These should be kept in mind when packaging for
+distribution.
Generally, egl_dri2
is preferred over egl_gallium
+when the system already has DRI drivers. As egl_gallium
is loaded
+before egl_dri2
when both are available, egl_gallium
+is disabled by default.
Developers
@@ -233,10 +252,6 @@ runtime.src/egl/
. The sources of the egl
state tracker can
be found at src/gallium/state_trackers/egl/
.
-The suggested way to learn to write a EGL driver is to see how other drivers
-are written. egl_glx
should be a good reference. It works in any
-environment that has GLX support, and it is simpler than most drivers.
Lifetime of Display Resources
Contexts and surfaces are examples of display resources. They might live @@ -244,8 +259,8 @@ longer than the display that creates them.
In EGL, when a display is terminated through eglTerminate
, all
display resources should be destroyed. Similarly, when a thread is released
-throught eglReleaseThread
, all current display resources should be
-released. Another way to destory or release resources is through functions
+through eglReleaseThread
, all current display resources should be
+released. Another way to destroy or release resources is through functions
such as eglDestroySurface
or eglMakeCurrent
.
When a resource that is current to some thread is destroyed, the resource
@@ -311,14 +326,6 @@ not be called with the sample display at the same time. If a driver has access
to an EGLDisplay
without going through the EGL APIs, the driver
should as well lock the display before using it.
-
TODOs
- --
-
- Pass the conformance tests -
- Better automatic driver selection:
EGL_DISPLAY
loads all -drivers and might eat too much memory.
-
-