EXT_device_drm_render_node

EXT_device_drm_render_node

James Jones
Simon Ser
Daniel Stone

James Jones, NVIDIA (jajones 'at' nvidia.com)

Draft

Version 1 - June 4th, 2021

EGL Extension #144

EGL device extension

Written based on the wording of the EGL 1.5 specification.

EGL_EXT_device_query is required.

EGL_EXT_device_drm interacts with this extension.

The EGL_EXT_device_drm extension provided a method for applications
to query the DRM device node file associated with a given
EGLDeviceEXT object. However, it was not clear whether it referred to
the primary or render device node. This extension adds an enum to
refer explicitly to the render device node and defines the existing
EGL_DRM_DEVICE_FILE_EXT as explicitly refering to the primary device
node.

None

None

Accepted as the <name> parameter of eglQueryDeviceStringEXT

    EGL_DRM_RENDER_NODE_FILE_EXT            0x3377

Add the following paragraph to the description of
eglQueryDeviceStringEXT:

"To obtain a DRM device file for the render node associated with an
EGLDeviceEXT, call eglQueryDeviceStringEXT with <name> set to
EGL_DRM_RENDER_NODE_FILE_EXT. The function will return a pointer to
a string containing the name of the device file (e.g.
"/dev/dri/renderDN"), or NULL if the device has no associated DRM
render node."

If EGL_EXT_device_drm is present, append the following to the
paragraph in the same section describing EGL_DRM_DEVICE_FILE_EXT:

"If the EGL_EXT_device_drm_render_node extension is supported, the
value returned will refer to a primary device node, and will be NULL
if the device has no associated DRM primary node. If
EGL_EXT_device_drm_render_node is not supported, the value returned
will refer to a primary device node if there exists one associated
with the device. Otherwise, it will refer to a render device node if
there exists one associated with the device. If neither exists, NULL
is returned."

1)  Should this extension clarify that EGL_DRM_DEVICE_FILE_EXT refers
    only to primary device nodes?

    RESOLVED: Yes, but only when this extension is supported. Existing
    implementations return render node paths for that string when no
    suitable primary node is available.

#2  (June 8th, 2021) James Jones
    - Added issue #1 and related spec changes.

#1  (June 4th, 2021) James Jones
    - Initial draft.