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1# SPDX-License-Identifier: GPL-2.02%YAML 1.23---4$id: http://devicetree.org/schemas/firmware/qemu,fw-cfg-mmio.yaml#5$schema: http://devicetree.org/meta-schemas/core.yaml#6 7title: QEMU Firmware Configuration8 9maintainers:10 - Rob Herring <robh@kernel.org>11 12description: |13 Various QEMU emulation / virtualization targets provide the following14 Firmware Configuration interface on the "virt" machine type:15 16 - A write-only, 16-bit wide selector (or control) register,17 - a read-write, 64-bit wide data register.18 19 QEMU exposes the control and data register to guests as memory mapped20 registers; their location is communicated to the guest's UEFI firmware in the21 DTB that QEMU places at the bottom of the guest's DRAM.22 23 The authoritative guest-side hardware interface documentation to the fw_cfg24 device can be found in "docs/specs/fw_cfg.txt" in the QEMU source tree.25 26 27properties:28 compatible:29 const: qemu,fw-cfg-mmio30 31 reg:32 maxItems: 133 description: |34 * Bytes 0x0 to 0x7 cover the data register.35 * Bytes 0x8 to 0x9 cover the selector register.36 * Further registers may be appended to the region in case of future interface37 revisions / feature bits.38 39 dma-coherent: true40 41required:42 - compatible43 - reg44 45additionalProperties: false46 47examples:48 - |49 50 fw-cfg@9020000 {51 compatible = "qemu,fw-cfg-mmio";52 reg = <0x9020000 0xa>;53 };54...55