[PATCH v2 04/10] dt-bindings: input: apple: Add DockChannel HID transport

[Michael Reeves via B4 Relay <devnull+michael.reeves077.gmail.com@kernel.org>]

From: Michael Reeves <michael.reeves077@gmail.com>

Apple internal keyboards and trackpads behind MTP are exposed through a
DockChannel HID transport.

Add the client binding tying together the RTKit ASC mailbox,
DockChannel mailbox, and MTP DART. The keyboard child can provide the
HID country code used by hid-apple to distinguish layout variants.

Describe the optional STM child, which supplies the device identifiers
and serial number shared by the HID interfaces.

Signed-off-by: Michael Reeves <michael.reeves077@gmail.com>

---
Conor's v1 Reviewed-by is not carried forward because v2 adds the STM binding.
---
 .../input/apple,t8112-dockchannel-hid.yaml         | 104 +++++++++++++++++++++
 MAINTAINERS                                        |   1 +
 2 files changed, 105 insertions(+)

diff --git a/Documentation/devicetree/bindings/input/apple,t8112-dockchannel-hid.yaml b/Documentation/devicetree/bindings/input/apple,t8112-dockchannel-hid.yaml
new file mode 100644
index 000000000..c25e072b6
--- /dev/null
+++ b/Documentation/devicetree/bindings/input/apple,t8112-dockchannel-hid.yaml
@@ -0,0 +1,104 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/input/apple,t8112-dockchannel-hid.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Apple DockChannel HID Transport
+
+maintainers:
+  - Michael Reeves <michael.reeves077@gmail.com>
+
+description:
+  HID transport for keyboard and trackpad devices connected via the
+  DockChannel FIFO mailbox on Apple Silicon SoCs. The endpoint includes a
+  small RTKit coprocessor called MTP which must be booted before the HID
+  transport becomes available.
+
+properties:
+  compatible:
+    oneOf:
+      - items:
+          - const: apple,t8112-dockchannel-hid
+      - items:
+          - enum:
+              - apple,t6020-dockchannel-hid
+              - apple,t6030-dockchannel-hid
+              - apple,t6031-dockchannel-hid
+              - apple,t8122-dockchannel-hid
+          - const: apple,t8112-dockchannel-hid
+
+  reg:
+    items:
+      - description: Coprocessor ASC registers
+      - description: Coprocessor SRAM/mailbox registers
+
+  reg-names:
+    items:
+      - const: coproc-asc
+      - const: coproc-sram
+
+  mboxes:
+    items:
+      - description: ASC mailbox used for RTKit control
+      - description: DockChannel FIFO mailbox used for HID packets
+
+  mbox-names:
+    items:
+      - const: asc
+      - const: dockchannel
+
+  iommus:
+    maxItems: 1
+
+  stm:
+    type: object
+    description:
+      STM interface providing the vendor, product and version identifiers
+      and serial number shared by the HID devices. When present, the host
+      must query this interface before registering the keyboard.
+    additionalProperties: false
+
+  keyboard:
+    type: object
+    properties:
+      hid-country-code:
+        $ref: /schemas/types.yaml#/definitions/uint32
+        description:
+          HID country code for the keyboard layout variant.
+
+    additionalProperties: false
+
+required:
+  - compatible
+  - reg
+  - reg-names
+  - mboxes
+  - mbox-names
+  - iommus
+
+additionalProperties: false
+
+examples:
+  - |
+    soc {
+        #address-cells = <2>;
+        #size-cells = <2>;
+
+        hid@24e400000 {
+            compatible = "apple,t8112-dockchannel-hid";
+            reg = <0x2 0x4e400000 0x0 0x4000>,
+                  <0x2 0x4ec00000 0x0 0x100000>;
+            reg-names = "coproc-asc", "coproc-sram";
+            mboxes = <&mtp_mbox>, <&mtp_dockchannel>;
+            mbox-names = "asc", "dockchannel";
+            iommus = <&mtp_dart 1>;
+
+            stm {
+            };
+
+            keyboard {
+                hid-country-code = <0>;
+            };
+        };
+    };
diff --git a/MAINTAINERS b/MAINTAINERS
index 0183c3e1c..7fe2ebb5e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2637,6 +2637,7 @@ F:	Documentation/devicetree/bindings/gpio/apple,smc-gpio.yaml
 F:	Documentation/devicetree/bindings/gpu/apple,agx.yaml
 F:	Documentation/devicetree/bindings/hwmon/apple,smc-hwmon.yaml
 F:	Documentation/devicetree/bindings/i2c/apple,i2c.yaml
+F:	Documentation/devicetree/bindings/input/apple,t8112-dockchannel-hid.yaml
 F:	Documentation/devicetree/bindings/input/touchscreen/apple,z2-multitouch.yaml
 F:	Documentation/devicetree/bindings/interrupt-controller/apple,*
 F:	Documentation/devicetree/bindings/iommu/apple,dart.yaml

-- 
2.55.0