Bindings/firmware/qemu,fw-cfg-mmio.yaml

   1 # SPDX-License-Identifier: GPL-2.0
   2 %YAML 1.2
   3 ---
   4 $id: http://devicetree.org/schemas/firmware/qemu,fw-cfg-mmio.yaml#
   5 $schema: http://devicetree.org/meta-schemas/core.yaml#
   6
   7 title: QEMU Firmware Configuration
   8
   9 maintainers:
  10   - Rob Herring <robh@kernel.org>
  11
  12 description: |
  13   Various QEMU emulation / virtualization targets provide the following
  14   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 mapped
  20   registers; their location is communicated to the guest's UEFI firmware in the
  21   DTB that QEMU places at the bottom of the guest's DRAM.
  22
  23   The authoritative guest-side hardware interface documentation to the fw_cfg
  24   device can be found in "docs/specs/fw_cfg.txt" in the QEMU source tree.
  25
  26
  27 properties:
  28   compatible:
  29     const: qemu,fw-cfg-mmio
  30
  31   reg:
  32     maxItems: 1
  33     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 interface
  37         revisions / feature bits.
  38
  39   dma-coherent: true
  40
  41 required:
  42   - compatible
  43   - reg
  44
  45 additionalProperties: false
  46
  47 examples:
  48   - |
  49
  50     fw-cfg@9020000 {
  51         compatible = "qemu,fw-cfg-mmio";
  52         reg = <0x9020000 0xa>;
  53     };
  54 ...