接前一篇文章：Linux设备驱动之gpio-keys（1）
本文内容参考：
Linux设备驱动之gpio-keys_linux gpio-keys-CSDN博客
GPIO-KEY的实现原理及使用方法_gpio-keys-CSDN博客
linux gpio key 实现方式_llinux gpio key 长按-CSDN博客
特此致谢！
上一回讲到了设备树（DTS）配置，给出了Linux内核代码中Documentation/devicetree/bindings/gpio/gpio-keys.txt文件，本回开始解析其具体内容。
二、详细解析
1. 设备树配置（DTS）
为了便于理解和回顾，再次贴出<Linux内核源码根目录>/Documentation/devicetree/bindings/gpio/gpio-keys.txt内容，如下：
bash
Device-Tree bindings for input/keyboard/gpio_keys.c keyboard driver
Required properties:
- compatible = "gpio-keys";
Optional properties:
- autorepeat: Boolean, Enable auto repeat feature of Linux input
subsystem.
- label: String, name of the input device.
Each button (key) is represented as a sub-node of "gpio-keys":
Subnode properties:
- gpios: OF device-tree gpio specification.
- interrupts: the interrupt line for that input.
- label: Descriptive name of the key.
- linux,code: Keycode to emit.
Note that either "interrupts" or "gpios" properties can be omitted, but not
both at the same time. Specifying both properties is allowed.
Optional subnode-properties:
- linux,input-type: Specify event type this button/key generates.
If not specified defaults to <1> == EV_KEY.
- debounce-interval: Debouncing interval time in milliseconds.
If not specified defaults to 5.
- wakeup-source: Boolean, button can wake-up the system.
(Legacy property supported: "gpio-key,wakeup")
- wakeup-event-action: Specifies whether the key should wake the
system when asserted, when deasserted, or both. This property is
only valid for keys that wake up the system (e.g., when the
"wakeup-source" property is also provided).
Supported values are defined in linux-event-codes.h:
EV_ACT_ASSERTED - asserted
EV_ACT_DEASSERTED - deasserted
EV_ACT_ANY - both asserted and deasserted
- linux,can-disable: Boolean, indicates that button is connected
to dedicated (not shared) interrupt which can be disabled to
suppress events from the button.
Example nodes:
gpio-keys {
compatible = "gpio-keys";
autorepeat;
up {
label = "GPIO Key UP";
linux,code = <103>;
gpios = <&gpio1 0 1>;
};
down {
label = "GPIO Key DOWN";
linux,code = <108>;
interrupts = <1 IRQ_TYPE_LEVEL_HIGH 7>;
};
...Required properties
-
- compatible = "gpio-keys";
该属性定义了设备的兼容性。
Optional properties
-
- autorepeat
布尔类型，启用input子系统的auto repeat特性。
-
- label
字符串类型，输入设备（如按键key）的名称。
Subnode properties
每一个按钮（button）/按键（key）都对应为"gpio-keys"的一个子节点，子节点的属性包括：
-
- gpios
开放固件设备树GPIO规范。
-
- interrupts
输入的中断线。
-
- label
按键的描述性名称。
-
- linux,code
input子系统所定义的按键代码。参见：include/dt-bindings/input/input.h关于keys和buttons的code定义。
注意："interrupts"或"gpios"属性都可以省略，但不能同时省略。允许同时指定这两个属性。
Optional subnode-properties
-
- linux,input-type
定义该key/button的event type（input子系统定义）。如果未指定，默认为1（EV_KEY）。
-
- debounce-interval
定义该key/button的去抖间隔。如果未指定，默认为5ms。
- -gpio-key,wakeup
布尔类型。标识该key可以唤醒系统，例如，Android系统的power-key。
-
- wakeup-event-action
指定按键在断言（有效）、取消断言（失效）或两者时，都应唤醒系统。
此属性仅对能唤醒系统的按键有效（例如，当同时提供"wakeup-source"属性时）。
支持的值在linux-event-codes.h中定义：
EV_ACT_ASSERTED - asserted
EV_ACT_DEASSERTED - deasserted
EV_ACT_ANY - both asserted and deasserted
-
- linux,can-disable:
布尔类型。表明某按钮连接到专用（非共享）中断，可以禁用该中断以抑制按钮的事件。
示例（结点）：
bash
gpio-keys {
compatible = "gpio-keys";
autorepeat;
up {
label = "GPIO Key UP";
linux,code = <103>;
gpios = <&gpio1 0 1>;
};
down {
label = "GPIO Key DOWN";
linux,code = <108>;
interrupts = <1 IRQ_TYPE_LEVEL_HIGH 7>;
};
...这样，Documentation/devicetree/bindings/gpio/gpio-keys.txt的内容就解析完了。更多内容请看下回。