DRM supports the writeback connector, so if you are DRM master then you can set that up with the same set of planes as your primary display and let it get on with it.Follow-up question: Does there exist a replacement for vc_dispmanx_snapshot() + vc_dispmanx_resource_read_data() for snapshotting the whole framebuffer view into userland memory pointer in KMS? Or locking/mapping the main framebuffer surface in KMS?
The intended use case would be for mirroring the contents of a screen over to a SPI connected display: https://github.com/juj/fbcp-ili9341
However if using Wayland via wlroots, then composition is done generally offline, and it is quite happy to drive an SPI connected display (as long as it has a DRM driver) as just another display device. There have already been a number of threads between myself and aBugsWorstNightmare on the subject of SPI connected displays and tinydrm or mipi-dbi-spi drivers for them.
Statistics: Posted by 6by9 — Mon Feb 05, 2024 6:36 pm