* QEMU Firmware Configuration bindings for ARM QEMU's arm-softmmu and aarch64-softmmu emulation / virtualization targets provide the following Firmware Configuration interface on the "virt" machine type: - A write-only, 16-bit wide selector (or control) register, - a read-write, 64-bit wide data register. QEMU exposes the control and data register to ARM guests as memory mapped registers; their location is communicated to the guest's UEFI firmware in the DTB that QEMU places at the bottom of the guest's DRAM. The authoritative guest-side hardware interface documentation to the fw_cfg device can be found in "docs/specs/fw_cfg.txt" in the QEMU source tree. Required properties: - compatible: "qemu,fw-cfg-mmio". - reg: the MMIO region used by the device. * Bytes 0x0 to 0x7 cover the data register. * Bytes 0x8 to 0x9 cover the selector register. * Further registers may be appended to the region in case of future interface revisions / feature bits. Example: / { #size-cells = <0x2>; #address-cells = <0x2>; fw-cfg@9020000 { compatible = "qemu,fw-cfg-mmio"; reg = <0x0 0x9020000 0x0 0xa>; }; };