[PATCH V2 5/7] dt-bindings: Add xen, dev-domid property description for xen-grant DMA ops

[Oleksandr Tyshchenko]

From: Oleksandr Tyshchenko <oleksandr_tyshchenko at epam.com>

Introduce Xen specific binding for the virtualized device (e.g. virtio)
to be used by Xen grant DMA-mapping layer in the subsequent commit.

This binding indicates that Xen grant mappings scheme needs to be
enabled for the device which DT node contains that property and specifies
the ID of Xen domain where the corresponding backend resides. The ID
(domid) is used as an argument to the grant mapping APIs.

This is needed for the option to restrict memory access using Xen grant
mappings to work which primary goal is to enable using virtio devices
in Xen guests.

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko at epam.com>
---
Changes RFC -> V1:
   - update commit subject/description and text in description
   - move to devicetree/bindings/arm/

Changes V1 -> V2:
   - update text in description
   - change the maintainer of the binding
   - fix validation issue
   - reference xen,dev-domid.yaml schema from virtio/mmio.yaml
---
 .../devicetree/bindings/arm/xen,dev-domid.yaml     | 37 ++++++++++++++++++++++
 Documentation/devicetree/bindings/virtio/mmio.yaml |  7 ++++
 2 files changed, 44 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/arm/xen,dev-domid.yaml

diff --git a/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml b/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
new file mode 100644
index 00000000..750e89e
--- /dev/null
+++ b/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
@@ -0,0 +1,37 @@
+# SPDX-License-Identifier: (GPL-2.0-only or BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/arm/xen,dev-domid.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Xen specific binding for virtualized devices (e.g. virtio)
+
+maintainers:
+  - Stefano Stabellini <sstabellini at kernel.org>
+
+select: true
+
+description:
+  This binding indicates that Xen grant mappings need to be enabled for
+  the device, and it specifies the ID of the domain where the corresponding
+  device (backend) resides. The property is required to restrict memory
+  access using Xen grant mappings.
+
+properties:
+  xen,dev-domid:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      The domid (domain ID) of the domain where the device (backend) is running.
+
+additionalProperties: true
+
+examples:
+  - |
+    virtio at 3000 {
+            compatible = "virtio,mmio";
+            reg = <0x3000 0x100>;
+            interrupts = <41>;
+
+            /* The device is located in Xen domain with ID 1 */
+            xen,dev-domid = <1>;
+    };
diff --git a/Documentation/devicetree/bindings/virtio/mmio.yaml b/Documentation/devicetree/bindings/virtio/mmio.yaml
index 10c22b5..29a0932 100644
--- a/Documentation/devicetree/bindings/virtio/mmio.yaml
+++ b/Documentation/devicetree/bindings/virtio/mmio.yaml
@@ -13,6 +13,9 @@ description:
   See https://www.oasis-open.org/committees/tc_home.php?wg_abbrev=virtio for
   more details.
 
+allOf:
+  - $ref: /schemas/arm/xen,dev-domid.yaml#
+
 properties:
   compatible:
     const: virtio,mmio
@@ -33,6 +36,10 @@ properties:
     description: Required for devices making accesses thru an IOMMU.
     maxItems: 1
 
+  xen,dev-domid:
+    description: Required when Xen grant mappings need to be enabled for device.
+    $ref: /schemas/types.yaml#/definitions/uint32
+
 required:
   - compatible
   - reg
-- 
2.7.4