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Primary node clarification for VK_EXT_physical_device_drm #2447

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Primary node clarification for VK_EXT_physical_device_drm #2447

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21 changes: 15 additions & 6 deletions appendices/VK_EXT_physical_device_drm.adoc
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Original file line number Diff line number Diff line change
Expand Up @@ -25,12 +25,17 @@ Unlike the EGL extension, this extension does not expose a string containing
the name of the device file and instead exposes device minor numbers.

DRM defines multiple device node types.
Each physical device may have one primary node and one render node
associated.
Physical devices may have no primary node (e.g. if the device does not have
a display subsystem), may have no render node (e.g. if it is a software
rendering engine), or may have neither (e.g. if it is a software rendering
engine without a display subsystem).
Each physical device can only be associated with a single underlying DRM
device, which may have one primary node and one render node.

Physical devices may have no primary node (e.g. it is not associated with a
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I don't think that case is possible, actually. A render node always has a primary node.

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I agree, I think the only case is the same as a software implementation which does not use DRM. Is it better to switch this text to something like "it always has the primary node if it is associated with a DRM device"?

DRM device) or may have no render node (e.g. if it uses a software rendering
engine), or may have neither (e.g. if it is a software rendering engine not
associated with any DRM device).

Note: This extension only returns primary node and render node from the same
DRM device for a Vulkan physical device. Implementations should not return
primary node and render node from different DRM devices.

To query DRM properties for a physical device, chain
slink:VkPhysicalDeviceDrmPropertiesEXT to slink:VkPhysicalDeviceProperties2.
Expand All @@ -44,5 +49,9 @@ include::{generated}/interfaces/VK_EXT_physical_device_drm.adoc[]

=== Version History

* Revision 2, 2024-11-07
** Clarification about the meaning of the primary node
** Clarification to not advertise more than one DRM device

* Revision 1, 2021-06-09
** First stable revision
2 changes: 1 addition & 1 deletion xml/vk.xml
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Expand Up @@ -22497,7 +22497,7 @@ typedef void* <name>MTLSharedEvent_id</name>;
</extension>
<extension name="VK_EXT_physical_device_drm" number="354" author="EXT" type="device" contact="Simon Ser @emersion" supported="vulkan" depends="VK_KHR_get_physical_device_properties2,VK_VERSION_1_1">
<require>
<enum value="1" name="VK_EXT_PHYSICAL_DEVICE_DRM_SPEC_VERSION"/>
<enum value="2" name="VK_EXT_PHYSICAL_DEVICE_DRM_SPEC_VERSION"/>
<enum value="&quot;VK_EXT_physical_device_drm&quot;" name="VK_EXT_PHYSICAL_DEVICE_DRM_EXTENSION_NAME"/>

<enum offset="0" extends="VkStructureType" name="VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_DRM_PROPERTIES_EXT"/>
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