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# SPDX-License-Identifier: GPL-2.0
%YAML 1.2
---
$id: http://devicetree.org/schemas/firmware/qemu,fw-cfg-mmio.yaml#
$schema: http://devicetree.org/meta-schemas/core.yaml#
title: QEMU Firmware Configuration bindings
maintainers:
- Rob Herring <robh@kernel.org>
description: |
Various QEMU 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 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.
properties:
compatible:
const: qemu,fw-cfg-mmio
reg:
maxItems: 1
description: |
* 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.
dma-coherent: true
required:
- compatible
- reg
additionalProperties: false
examples:
- |
fw-cfg@9020000 {
compatible = "qemu,fw-cfg-mmio";
reg = <0x9020000 0xa>;
};
...
|
