gpiod - 在设备树中使用标签

我想用libgpiod通过自定义板上的用户空间控制一些 GPIO。我有一个 i.MX6UL 处理器，它有数百个引脚，我将只使用其中 8 个（作为 GPIO）。

我读到了关于libgpiod因为它正在取代旧的 sysfs API，我很高兴您可以为每个 GPIO 指定标签。处理器的 GPIO 块类似于以下代码块，并且已经gpio-controller属性集。 （摘自Linux内核v4.14）

gpio2: gpio@20a0000 {
    compatible = "fsl,imx6ul-gpio", "fsl,imx35-gpio";
    reg = <0x020a0000 0x4000>;
    interrupts = <GIC_SPI 68 IRQ_TYPE_LEVEL_HIGH>,
             <GIC_SPI 69 IRQ_TYPE_LEVEL_HIGH>;
    gpio-controller;
    #gpio-cells = <2>;
    interrupt-controller;
    #interrupt-cells = <2>;
    gpio-ranges = <&iomuxc 0 49 16>, <&iomuxc 16 111 6>;
};

我想使用该控制器的单个引脚，因此我添加了以下块：

&gpio2 {
    resetl0 {
        //gpio-hog;
        output-high;
        line-name = "COBO0_ResetL";
        gpios = <15 1>;
    };
};

如果没有gpio-hog财产，gpioinfo工具无法向我显示标签，如果我省略输出高/低，也是如此。有了属性，标签正确显示，但是gpio被标记为used，所以我无法从用户空间进行控制。 (设备或资源繁忙)

简而言之： 我需要一种在设备树中设置标签的方法，我可以从用户空间读取该标签并控制 gpios。我已经看到了gpio-line-names在 RPi 设备树中，但我不想在仅使用一个时将整个库指定为 NC。是否可以与libgpiod? How?

我在 Odroid-N2 内核 v5.4 上进行了测试。

介子-g12b-odroid-n2.dts

&gpio {
    gpio-line-names = 
        /* GPIOZ */
        "", "", "", "", "", "", "", "",
        "", "", "", "", "", "", "", "",
        /* GPIOH */
        "", "", "", "", "", "", "", "",
        "",
        /* BOOT */
        "", "", "", "", "", "", "", "",
        "", "", "", "", "", "", "", "",
        /* GPIOC */
        "", "", "", "", "", "", "", "",
        /* GPIOA */
        "44", "46", "45", "47",
        "26", "",   "",   "",
        "",   "",   "",   "42",
        "32", "7",  "27", "28",
        /* GPIOX */
        "16", "18", "22", "11",
        "13", "33", "35", "15",
        "19", "21", "24", "23",
        "8",  "0",  "29", "31",
        "12", "3",  "5",  "36";

    usb-hub {
        gpio-hog;
        gpios = <GPIOH_4 GPIO_ACTIVE_HIGH>;
        output-high;
        line-name = "usb-hub-reset";
    };
};

输出gpioinfo

gpiochip0 - 85 lines:
...
    line  20:      unnamed "usb-hub-reset" input active-high [used]
...
    line  49:         "44"       unused   input  active-high 
    line  50:         "46"       unused   input  active-high 
    line  51:         "45"       unused   input  active-high 
    line  52:         "47"       unused   input  active-high 
    line  53:         "26"       unused   input  active-high 
...
    line  60:         "42"       unused   input  active-high 
    line  61:         "32"       unused   input  active-high 
    line  62:          "7"       unused   input  active-high 
    line  63:         "27"       unused   input  active-high 
    line  64:         "28"       unused   input  active-high 
    line  65:         "16"       unused   input  active-high 
    line  66:         "18"       unused   input  active-high 
    line  67:         "22"       unused   input  active-high 
    line  68:         "11"       unused   input  active-high 
    line  69:         "13"       unused   input  active-high 
    line  70:         "33"       unused   input  active-high 
    line  71:         "35"       unused   input  active-high 
    line  72:         "15"       unused   input  active-high 
    line  73:         "19"       unused   input  active-high 
    line  74:         "21"       unused   input  active-high 
    line  75:         "24"       unused   input  active-high 
    line  76:         "23"       unused   input  active-high 
    line  77:          "8"       unused   input  active-high 
    line  78:          "0"       unused   input  active-high 
    line  79:         "29"       unused   input  active-high 
    line  80:         "31"       unused   input  active-high 
    line  81:         "12"       unused   input  active-high 
    line  82:          "3"       unused   input  active-high 
    line  83:          "5"       unused   input  active-high 
    line  84:         "36"       unused   input  active-high 
...

gpioinfo将“gpio-line-names”显示为名称，将“line-name”显示为消费者。