linux-kernel - [PATCH RFC v1 2/2] devicetree: bindings: bus: add Wiegand driver documentation

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Date:   Thu, 28 Jul 2022 11:17:12 +0200
From:   Martin Zaťovič <m.zatovic1@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     devicetree@...r.kernel.org, mani@...nel.org,
        hemantk@...eaurora.org, elder@...aro.org, f.fainelli@...il.com,
        linus.walleij@...aro.org, Michael.Srba@...nam.cz,
        jeffrey.l.hugo@...il.com, gregkh@...uxfoundation.org,
        bjorn.andersson@...aro.org, saravanak@...gle.com,
        krzysztof.kozlowski+dt@...aro.org, robh+dt@...nel.org,
        Martin Zaťovič <m.zatovic1@...il.com>
Subject: [PATCH RFC v1 2/2] devicetree: bindings: bus: add Wiegand driver documentation

Wiegand write-only driver requires definitions of two GPIO lines
in the devicetree. This adds the documentation of their
definitions.

Signed-off-by: Martin Zaťovič <m.zatovic1@...il.com>
---
 .../devicetree/bindings/bus/wiegand-gpio.yaml | 66 +++++++++++++++++++
 MAINTAINERS                                   |  1 +
 2 files changed, 67 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/bus/wiegand-gpio.yaml

diff --git a/Documentation/devicetree/bindings/bus/wiegand-gpio.yaml b/Documentation/devicetree/bindings/bus/wiegand-gpio.yaml
new file mode 100644
index 000000000000..74733aadc61e
--- /dev/null
+++ b/Documentation/devicetree/bindings/bus/wiegand-gpio.yaml
@@ -0,0 +1,66 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/bus/wiegand-gpio.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Wiegand write-only GPIO driver
+
+maintainers:
+  - Martin Zaťovič <m.zatovic1@...il.com>
+
+description: |
+  Wiegand interface is a wiring standard popularized in the 1980s. To this day
+  many card readers, fingerprint readers, sensors, etc. use Wiegand interface
+  particularly for access control applications. It utilizes two wires to
+  transmit the data - D0 and D1.
+
+  Both data lines are initially pulled up. To send a bit of value 1, the D1
+  line is set low. Similarly to send a bit of value 0, the D0 line is set low.
+  Standard Wiegand formats include 26, 36 and 37 bit and they reserve the first
+  and last bits for parity. The first(MSB) parity bit is set to 1 if the parity
+  of the first half of the payload is odd. The last(LSB) parity bit is set to 1
+  if the parity of the second half of the payload even.
+
+properties:
+  $nodename:
+    pattern: "^wiegand-gpio(@[0-9a-f]+)?$"
+
+  compatible:
+    contains:
+      const: gpio,wiegand-gpio
+    description:
+      Shall contain "wiegand-gpio" for the driver to match with this node.
+
+  wiegand-data-hi-gpios:
+    description:
+      gpio used to transmit bits the value of which is 1, it should be
+      flagged as active high with GPIO_ACTIVE_HIGH from
+      <dt-bindings/gpio/gpio.h>.
+    maxItems: 1
+
+  wiegand-data-lo-gpios:
+    description:
+      gpio used to transmit bits the value of which is 1, it should be
+      flagged as active high with GPIO_ACTIVE_HIGH from
+      <dt-bindings/gpio/gpio.h>.
+    maxItems: 1
+
+required:
+  - compatible
+  - wiegand-data-hi-gpios
+  - wiegand-data-lo-gpios
+
+additionalProperties: true
+
+examples:
+  - |
+    wiegand-gpio {
+        compatible = "wiegand-gpio";
+        pinctrl-names = "default";
+        pinctrl-0 = <&pinctrl_uart1_wiegand>;
+        wiegand-data-hi-gpios = <&gpio2 1 GPIO_ACTIVE_HIGH>;
+        wiegand-data-lo-gpios = <&gpio2 2 GPIO_ACTIVE_HIGH>;
+        status = "okay";
+    };
diff --git a/MAINTAINERS b/MAINTAINERS
index 9a519530e44e..c7db1e41cc02 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -21589,6 +21589,7 @@ F:	drivers/rtc/rtc-sd3078.c
 WIEGAND WRITE-ONLY GPIO DRIVER
 M:	Martin Zaťovič <m.zatovic1@...il.com>
 S:	Maintained
+F:	Documentation/devicetree/bindings/bus/wiegand-gpio.yaml
 F:	drivers/bus/wiegand-gpio.c
 F:	drivers/bus/wiegand-gpio.h
 
-- 
2.37.1