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[v4] Query property when checking availability of virtual displays

Paz Zcharya requested to merge pazz1/drm-hwcomposer:query-property-virtual-displays into main

The current implementation of getMaxVirtualDisplayCount function relies on the number of writeback connectors, but doesn't consider the availability of CRTCs. Since CRTCs can only be bound to a single pipeline, even though there are available writeback connectors, we might fail to create a virtual pipeline if the CRTCs are being used.

This leads to failures in the CreateVirtualDisplay and SetOutputBuffer VTS tests because the tests expect the creation of a virtual pipeline to work based on the positive value returned by getMaxVirtualDisplayCount.

The virtual display feature in drm-hwcomposer is experimental and currently unused. To address test failures, modify the function getMaxVirtualDisplayCount to return 0 unless the property vendor.hwc.drm.enable_virtual_display is explicitly set to true.

More context:

  • Original issue: #102 (closed)
  • [v1] merge request: !275 (closed)
    • Suggested changing the implementation of getMaxVirtualDisplayCount to report virtual display count based on available CRTCs.
  • [v2] merge request: !278 (closed)
    • Suggested changing the implementation of getMaxVirtualDisplayCount to report virtual display count based on available pipelines.
  • [v3]: Used debug.sf.enable_hwc_vds, which ties drm-hwcomposer to surfaceflinger where the two should be uncoupled. Replaced with a drm-composer specific property, vendor.hwc.drm.enable_virtual_display, in v4.
Edited by Paz Zcharya

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