gpiod-在devicetree中使用标签 [英] gpiod - use labels in devicetree

问题描述

我想使用 libgpiod 通过自定义板上的用户空间来控制一些GPIO.我有一个i.MX6UL处理器，它具有数百个引脚，我将仅使用其中的8个引脚(作为GPIO).

I want to use libgpiod to control a few GPIOs via userspace on a custom board. I have an i.MX6UL processor, which has hundreds of pins, I'll use only 8 of them (as GPIOs).

我读到有关 libgpiod 的信息，因为它正在替换旧的sysfs API，并且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，并且已经设置了 gpio-controller 属性.(摘自Linux内核v4.14)

I read about the libgpiod as it is replacing the old sysfs API, and I'm happy that you can specify labels for each GPIO. The GPIO block of the processor looks like the following code block and has already the gpio-controller property set. (Taken from Linux kernel 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，因此添加了以下代码块:

I want to use a single pin of this controller, so I added the following block:

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

如果没有 gpio-hog 属性， gpioinfo 工具将无法显示标签，如果我省略了output-high/low.使用该属性，可以正确显示标签，但是gpio被标记为 used ，因此我无法从用户空间进行控制.(设备或资源繁忙)

Without the gpio-hog property, the gpioinfo tool is unable to show me the labels, same if I omit the output-high/low. With the property, the label is correctly displayed, but the gpio is marked as used, so I cannot control from userspace. (Device or resource busy)

简而言之:我需要一种在设备树中设置标签的方法，可以从用户空间读取标签并控制gpios.我已经在RPi设备树中看到 gpio-line-names ，但是当只使用一个库时，我不想将整个库指定为NC. libgpiod 是否可以?怎么样?

So in short: I need a way to set a label in device tree, which I'm able to read from userspace and to control the gpios. I already saw the gpio-line-names in the RPi devicetree, but I don't want to specify the whole bank as NC, when using only one. Is it possible with libgpiod? How?

推荐答案

我在Odroid-N2内核v5.4上进行了测试.

I tested on Odroid-N2 kernel v5.4.

meson-g12b-odroid-n2.dts

meson-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";
    };
};

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"显示为使用者.

gpioinfo displayed 'gpio-line-names' as a name and 'line-name' as a consumer.

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