I have a CM4 on the CM4 I/O board. I am working in bare metal and have the framebuffer address and read/write operations working. If I have one monitor plugged into either HDMI0 or HDMI1, that monitor displays everything correctly. If I plug a monitor into HDMI0 and a monitor into HDMI1, when I request a framebuffer address using the mailbox, I get a framebuffer for HDMI0 and the monitor attached to HDMI0 displays everything correctly. The monitor plugged into HDMI1 displays the rainbow square so I know it's attached and seen by the firmware.
In a bare metal system, I want to attach two monitors to the two HDMI ports and have different output going to each.
My question is this: How can I get a second framebuffer address for HDMI1 when the first framebuffer address requested though the mailbox is assigned to HDMI0?
In a bare metal system, I want to attach two monitors to the two HDMI ports and have different output going to each.
My question is this: How can I get a second framebuffer address for HDMI1 when the first framebuffer address requested though the mailbox is assigned to HDMI0?
Statistics: Posted by ibalked — Tue Dec 16, 2025 8:28 pm