[PATCH 1/5] dt-bindings: Add Bao IPC shared memory driver binding

joaopeixoto
2025-12-24T15:39:30Z

From: João Peixoto <joaopeixoto@osyx.tech>

This patch adds a Device Tree binding for the Bao IPC shared memory
device, which provides a standardized description of the hardware
interface used for inter-VM communication in Bao-based systems.

The binding documents the following properties:

- compatible: "bao,ipcshmem"
- reg: Memory region for the shared memory device
- id: Unique device identifier
- read-channel: [offset, size] for reading from the shared memory
- write-channel: [offset, size] for writing to the shared memory
- interrupts: Interrupts used by the device

This enables kernel drivers and userspace tools to correctly
instantiate and configure Bao IPC shared memory devices based
on the DT description, facilitating efficient communication
between VMs.

Signed-off-by: João Peixoto <joaopeixoto@osyx.tech>
---
.../devicetree/bindings/bao/ipcshmem.yaml | 99 +++++++++++++++++++
.../devicetree/bindings/vendor-prefixes.yaml | 2 +
2 files changed, 101 insertions(+)
create mode 100644 Documentation/devicetree/bindings/bao/ipcshmem.yaml

diff --git a/Documentation/devicetree/bindings/bao/ipcshmem.yaml b/Documentation/devicetree/bindings/bao/ipcshmem.yaml
new file mode 100644
index 000000000000..398ac610c29f
--- /dev/null
+++ b/Documentation/devicetree/bindings/bao/ipcshmem.yaml
@@ -0,0 +1,99 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/bao/ipcshmem.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: Bao IPC Shared Memory Device
+
+maintainers:
+ - José Martins <jose@osyx.tech>
+ - David Cerdeira <davidmcerdeira@osyx.tech>
+ - João Peixoto <joaopeixoto@osyx.tech>
+
+description: |
+ Shared memory based communication device for Bao hypervisor guests.
+ It allows the kernel to interface with guests running under
+ the Bao hypervisor, providing a character device interface
+ for exchanging data through dedicated shared-memory regions.
+
+properties:
+ compatible:
+ const: "bao,ipcshmem"
+
+ reg:
+ description: |
+ Memory resource for the shared memory device.
+ maxItems: 4
+ type: array
+ items:
+ type: integer
+
+ id:
+ description: Driver instance ID
+ type: integer
+ minimum: 0
+
+ read-channel:
+ description: |
+ Defines the shared-memory region used by the guest → host data path.
+
+ The value is a 2-cell array describing a sub-region inside the main
+ `reg` area:
+ - The first cell is the byte offset from the beginning of the
+ shared-memory region specified in `reg`.
+ - The second cell is the size of the readable region in bytes.
+
+ The driver will only read data from this sub-region.
+ type: array
+ items:
+ type: integer
+ minItems: 2
+ maxItems: 2
+
+ write-channel:
+ description: |
+ Defines the shared-memory region used by the host → guest data path.
+
+ The value is a 2-cell array describing a sub-region inside the main
+ `reg` area:
+ - The first cell is the byte offset from the beginning of the
+ shared-memory region specified in `reg`.
+ - The second cell is the size of the writable region in bytes.
+
+ The driver will only write data into this sub-region.
+ type: array
+ items:
+ type: integer
+ minItems: 2
+ maxItems: 2
+
+ interrupts:
+ description: |
+ Interrupt specification for the device.
+ type: array
+ items:
+ type: integer
+ minItems: 3
+ maxItems: 3
+
+required:
+ - compatible
+ - reg
+ - id
+ - read-channel
+ - write-channel
+ - interrupts
+
+additionalProperties: false
+
+examples:
+ - |
+ bao-ipc@f0000000 {
+ compatible = "bao,ipcshmem";
+ reg = <0x0 0xf0000000 0x0 0x00010000>;
+ read-channel = <0x0 0x2000>;
+ write-channel = <0x2000 0x2000>;
+ interrupts = <0 52 1>;
+ id = <0>;
+ };
diff --git a/Documentation/devicetree/bindings/vendor-prefixes.yaml b/Documentation/devicetree/bindings/vendor-prefixes.yaml
index c7591b2aec2a..c047fbd6b91a 100644
--- a/Documentation/devicetree/bindings/vendor-prefixes.yaml
+++ b/Documentation/devicetree/bindings/vendor-prefixes.yaml
@@ -223,6 +223,8 @@ patternProperties:
description: Shenzhen AZW Technology Co., Ltd.
"^baikal,.*":
description: BAIKAL ELECTRONICS, JSC
+ "^bao,.*":
+ description: Bao Hypervisor
"^bananapi,.*":
description: BIPAI KEJI LIMITED
"^beacon,.*":
--
2.43.0