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Name
EXT_device_query
Name Strings
EGL_EXT_device_query
Contributors
James Jones, NVIDIA (jajones 'at' nvidia.com)
Jamie Madill, Google (jmadill 'at' google.com)
Contacts
Jamie Madill, Google (jmadill 'at' google.com)
Status
Complete.
Version
Version 1 - Mar 25rd, 2015
Number
EGL Extension #89
Extension Type
EGL client extension
Dependencies
Written against the wording of EGL 1.5.
Requires EGL 1.5 or an earlier verison of EGL with the
EGL_EXT_client_extensions extension.
Overview
Increasingly, EGL and its client APIs are being used in place of
"native" rendering APIs to implement the basic graphics
functionality of native windowing systems. This creates demand
for a method to access native GPU or device objects directly
rather than calling EGL or GL entry points.
This extension defines the method for an application to query
native device objects from an EGL Display.
New Types
This is the type of a handle that represents an EGLDeviceEXT
object.
typedef void* EGLDeviceEXT;
If EGL 1.5 is not supported, the following type is added, as
defined in the EGL 1.5 specification:
typedef intptr_t EGLAttrib;
New Functions
EGLBoolean eglQueryDeviceAttribEXT(EGLDeviceEXT device,
EGLint attribute,
EGLAttrib *value);
const char *eglQueryDeviceStringEXT(EGLDeviceEXT device,
EGLint name);
EGLBoolean eglQueryDisplayAttribEXT(EGLDisplay dpy,
EGLint attribute,
EGLAttrib *value);
New Tokens
Functions with a return type of EGLDeviceEXT will return this
value on failure:
EGL_NO_DEVICE_EXT ((EGLDeviceEXT)0)
This error value will be generated by functions that take an
EGLDeviceEXT object as a parameter:
EGL_BAD_DEVICE_EXT 0x322B
Accepted by the <attribute> parameter of
eglQueryDisplayAttribEXT:
EGL_DEVICE_EXT 0x322C
Add a new section "2.1.2 Devices" after "2.1.1 Scalar Types"
All EGL operations occur on an EGLDeviceEXT. However, devices
themselves expose no functionality. They are simple abstract
objects that exist only for the sake of enumeration and
defining a namespace.
Modify the last sentence of section "2.1.3" Displays" to read:
Besides devices, objects are always specified by the combination
of an EGLDisplay parameter with a parameter representing the
handle of the object.
Add a new extension type to the list in section "2.8 Extensions"
Device Extensions
A *device extension* adds functionality to an individual
EGLDeviceEXT. Different instances of EGLDeviceEXT may support
different sets of device extensions
Add a new error to section "3.1 Errors"
EGL_BAD_DEVICE_EXT
An EGLDeviceEXT argument does not refer to a valid
EGLDeviceEXT. Any command taking an EGLDeviceEXT parameter
may generate this error.
Add a section "3.2 Devices" after "3.1 Errors"
To query the properties of a device, use:
EGLBoolean eglQueryDeviceAttribEXT(EGLDeviceEXT device,
EGLint attribute,
EGLAttrib *value);
On success, EGL_TRUE is returned and the requested attribute value
is returned in <value>. Currently there are no valid values of
<attribute> defined.
On failure, EGL_FALSE is returned. An EGL_BAD_ATTRIBUTE error is
generated if <attribute> is not a valid attribute. An
EGL_BAD_DEVICE_EXT error is generated if <device> is not a valid
EGLDeviceEXT.
const char *eglQueryDeviceStringEXT(EGLDeviceEXT device,
EGLint name);
returns a pointer to a static, zero-terminated string describing
some aspect of the specified EGLDeviceEXT. <name> must be
EGL_EXTENSIONS.
The EGL_EXTENSIONS string describes which device extensions are
supported by <device>. The string is of the same format specified
for display and client extension strings in section 3.4. Note that
device extensions are properties of the device, and are distinct
from other extension strings.
On failure, NULL is returned. An EGL_BAD_DEVICE_EXT error is
generated if <device> is not a valid EGLDeviceEXT. An
EGL_BAD_PARAMETER error is generated if <name> is not one of the
values described above.
Add a section "3.4 Display Attributes" after "3.3 EGL Versioning"
To query attributes of an initialized display, use:
EGLBoolean eglQueryDisplayAttribEXT(EGLDisplay dpy,
EGLint name,
EGLAttrib *value);
On success, EGL_TRUE is returned. If <name> is EGL_DEVICE_EXT,
the EGLDeviceEXT associated with <dpy> is returned in <value>.
All displays have an associated EGLDeviceEXT, regardless of how
they were created. A successful query of EGL_DEVICE_EXT will
never return EGL_NO_DEVICE_EXT.
On failure, EGL_FALSE is returned. An EGL_NOT_INITIALIZED error
is generated if EGL is not initialized for <dpy>. An
EGL_BAD_ATTRIBUTE error is generated if <name> is not a valid
value.
Because the EGLDeviceEXT is a property of <dpy>, any use of an
associated EGLDeviceEXT after <dpy> has been terminated gives
undefined results. Querying an EGL_DEVICE_EXT from <dpy> after a
call to eglTerminate() (and subsequent re-initialization) may
return a different value.
Issues
None.
Revision History:
#1 (Mar 25rd, 2015) Jamie Madill
- Initial Draft based on EGL_EXT_device_base
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