Hello, I'm looking at the available options to support overlays in the display pipeline of the i.MX7. The LCDIF itself unfortunaltey doesn't support overlays, the feature being implemented in the PXP. A driver for the PXP is available but only supports older SoCs whose PXP doesn't support overlays. This driver is implemented as a V4L2 mem2mem driver, which makes support of additional input channels impossible. Here are the options I can envision: - Extend the existing PXP driver to support multiple channels. This is technically feasible, but will require moving away from the V4L2 mem2mem framework, which would break userspace. I don't think this path could lead anywhere. - Write a new PXP driver for the i.MX7, still using V4L2, but with multiple video nodes. This would allow blending multiple layers, but would require writing the output to memory, while the PXP has support for direct connections to the LCDIF (through small SRAM buffers). Performances would thus be suboptimal. The API would also be awkward, as using the PXP for display would require usage of V4L2 in applications. - Extend the mxsfb driver with PXP support, and expose the PXP inputs as KMS planes. The PXP would only be used when available, and would be transparent to applications. This would however prevent using it separately from the display (to perform multi-pass alpha blending for instance). What would be the best option going forward ? Would any of you, by any chance, have already started work in this area ? -- Regards, Laurent Pinchart
