C 从内核空间配置LED触发器的参数

我在做一个嵌入式项目。我们的主板使用Linux内核v3.16.7。我正在研究支持两个外围LED来监控活动。我已经成功地将引导过程修改为in

/sys/class/led/

，这非常好。我还将a连接到led上，因此我可以从

/sys/class/led/actled1\：绿色/

中拍摄

echo 1>镜头，并且led闪烁。正是我想要的

但是，我想在引导期间实例化驱动程序时为每个LED配置延迟，我不清楚如何做到这一点。驱动程序在
/sys/class/led/actled1\：green/
中创建sysfs条目，称为
delay\u on
和
delay\u off
，我可以从用户空间写入这些条目来配置延迟，但在实例化过程中应该可以从内核空间设置它们的初始值。我还希望能够设置
invert
参数（这只是另一个sysfs条目，就像延迟一样）

从内核空间实例化驱动程序时，如何配置led触发器的参数？

下面是我如何实例化LED GPIO的。首先，我设置了所需的结构：

static struct gpio_led my_leds[] __initdata = {
    {
        .name = "actled1:green",
        .default_trigger = "oneshot"
        .gpio = ACTIVITY_LED_GPIO_BASE + 0,
        .active_low = true,
    },
    {
        .name = "actled2:red",
        .default_trigger = "oneshot"
        .gpio = ACTIVITY_LED_GPIO_BASE + 1,
        .active_low = true,
    },
};

static struct gpio_led_platform_data my_leds_pdata __initdata = {
    .num_leds = ARRAY_SIZE(my_leds),
    .leds = my_leds,
};

然后，我调用此函数来创建平台设备：

static int __init setup_my_leds (void)
{
    struct platform_device *pdev;
    int ret;

    pdev = platform_device_alloc("leds-gpio", -1);
    if (!pdev) {
        return -ENOMEM;
    }

    ret = platform_device_add_data(pdev,
                    &my_leds_pdata,
                    sizeof(my_leds_pdata));

    if (ret < 0) {
        platform_device_put(pdev);
        return ret;
    }

    ret = platform_device_add(pdev);
    if (ret < 0) {
        platform_device_put(pdev);
        return ret;
    }

    return 0;
}

static int\uuuu init setup\u my\u指示灯（无效）
{
结构平台设备*pdev；
int ret；
pdev=平台、设备、所有（“LED gpio”、-1）；
如果（！pdev）{
return-ENOMEM；
}
ret=平台设备添加数据（pdev，
&我的数据，
sizeof（my_LED_pdata））；
如果（ret<0）{
平台设备输出（pdev）；
返回ret；
}
ret=平台设备添加（pdev）；
如果（ret<0）{
平台设备输出（pdev）；
返回ret；
}
返回0；
}

gpio_led
struct的定义在中，而
gpio_led_平台_数据的定义在中。
platform\u device\u add\u data
的定义在中

为了回答这个问题，查看oneshot触发器（）的源代码可能会很有用。与此相关的还有“LED gpio”驱动程序（）

我怀疑答案在和相关联的函数中，但我没有看到任何处理我需要的数据的函数


为了解决我无意中遗漏的一些信息：

引导加载程序设置内核参数，我们不能修改引导加载程序。那很好；我想设置的值是常量，我可以硬编码它们
驱动程序在编译时被烘焙到内核中（我猜是由引导加载程序加载的），而不是稍后使用modprobe加载
.ko
我想要一种设置任意触发参数的通用方法，而不仅仅是oneshot的
delay\u on
/
delay\u off
。例如，oneshot的
invert
参数
我完全可以修改oneshot/创建新触发器。事实上，一旦我使用oneshot，我需要创建一个新的触发器来扩展oneshot（这也是我需要设置任意参数的原因）
如中所示，延迟总是使用
DEFAULT\u delay
初始化。不幸的是，如果您想在启动时配置不同的值，这是一种必须实现的机制。
有一些问题，我想我已经找到了解决方案，但即使您提供了大量信息，也缺少一些内容，因此我将列举所有可能的场景，请耐心等待

（1） 获取要设置的初始值。我想你已经知道了，但是。。。您可以从内核cmdline解析中获得这些值（例如，您将值添加到/boot/grub2/grub.cfg中作为
myleds.delay\u on=…
。如果您是通过
modprobe
加载的，您可以设置一个模块参数。这些也可以是配置文件，如
myleds.config\u文件=/etc/sysconfig/myleds.conf

（2） 您可以在设置“我的”指示灯中设置它们[除了oneshot\u trig\u activate的顽抗之外--我们很快就会处理它]。从
drivers/base/platform.c
：

/**
 * arch_setup_pdev_archdata - Allow manipulation of archdata before its used
 * @pdev: platform device
 *
 * This is called before platform_device_add() such that any pdev_archdata may
 * be setup before the platform_notifier is called.  So if a user needs to
 * manipulate any relevant information in the pdev_archdata they can do:
 *
 *  platform_device_alloc()
 *  ... manipulate ...
 *  platform_device_add()
 *
 * And if they don't care they can just call platform_device_register() and
 * everything will just work out.
 */

因此，考虑到这一点，让我们稍微更改一下设置功能：

static int __init setup_my_leds (void)
{
    struct platform_device *pdev;
    int ret;

    // get initial values you want to set, possibly storing away for later use
    my_leds_get_init_values(...);

    pdev = platform_device_alloc("leds-gpio", -1);
    if (!pdev) {
        return -ENOMEM;
    }

    // Choice (1): set your initial values in my_leds_pdata here
    my_leds_set_init_values(&my_leds_pdata);

    // NOTE: just does kmemdup and sets pdev->dev.platform_data
    ret = platform_device_add_data(pdev,
                    &my_leds_pdata,
                    sizeof(my_leds_pdata));

    if (ret < 0) {
        platform_device_put(pdev);
        return ret;
    }

    // Choice (2): set your initial values in pdev->dev.platform_data here
    my_leds_set_init_values(pdev->dev.platform_data);

    ret = platform_device_add(pdev);
    if (ret < 0) {
        platform_device_put(pdev);
        return ret;
    }

    return 0;
}

正如Craig回答的那样，应该是内核命令行选项，但在嵌入式系统中可能会出现问题，引导加载程序传递命令行参数，并且引导加载程序无法修改，它们通常是OTP。在这种情况下，我只看到两个选项

内核init函数中的硬编码

由于mac地址存储在eeprom中，以便nic驱动程序读取，因此，如果值可以存储在闪存（nor）中，则在引导时读取该值。这可以在内核引导期间创建mtd分区后完成

设备树、ACPI或内置设备属性是您的选择。在任何情况下，您都必须为驱动程序支持的属性编写代码。我很乐意为oneshot编写自己的修改，但如果我编写了一个新函数（例如，
set\u delay\u on（int）
），我如何从我的内核空间实例化代码中调用它？我实际上没有驱动程序或任何东西的句柄。你是一个救命恩人。这个答案非常有用。我将研究你提到的一些事情并向你汇报。好的，我看到这允许我设置
延迟
和
延迟
using平台数据。我可以使用此技术设置其他参数，如
invert
吗？我这样问是因为它看起来是直接设置结构的显式提到的
delay\u on
和
delay\u off
字段，但是
invert
字段不是该结构的一部分（也不是其他触发器的任意参数）。因此，此方法是否仅限于配置
delay\u on
和
delay\u off
参数？@WoodrowBarlow您是正确的（例如，invert是
/*
 * One-shot LED Trigger
 *
 * Copyright 2012, Fabio Baltieri <fabio.baltieri@gmail.com>
 *
 * Based on ledtrig-timer.c by Richard Purdie <rpurdie@openedhand.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/ctype.h>
#include <linux/slab.h>
#include <linux/leds.h>
#include "../leds.h"

// C: we need to get access to the init data populated by the setup function
// we have the "clean way" with a struct definition inside a header file and
// the "dirty way" using three separate int globals
// in either case, the externs referenced here must be defined in the "my_leds"
// driver as global

// C: the "clean way"
// (1) requires that we have a path to the .h (e.g. -I<whatever)
// (2) this would be easier/preferable for the "Option (C)"
// (3) once done, easily extensible [probably not a consideration here]
#ifdef MYLED_USESTRUCT
#include "whatever/myled_init.h"
extern struct myled_init myled_init;

// C: the "ugly way"
// (1) no need to use a separate .h file
// (2) three separate global variables is wasteful
// (3) more than three, and we really should consider the "struct"
#else
extern int myled_init_delay_on;
extern int myled_init_delay_off;
extern int myled_init_invert;
#endif

#define DEFAULT_DELAY 100

// oneshot trigger driver private data
struct oneshot_trig_data {
    unsigned int invert;                // current invert state
};

// arm oneshot sequence from sysfs write to shot file
static ssize_t led_shot(struct device *dev,
        struct device_attribute *attr, const char *buf, size_t size)
{
    struct led_classdev *led_cdev = dev_get_drvdata(dev);
    struct oneshot_trig_data *oneshot_data = led_cdev->trigger_data;

    led_blink_set_oneshot(led_cdev,
            &led_cdev->blink_delay_on, &led_cdev->blink_delay_off,
            oneshot_data->invert);

    /* content is ignored */
    return size;
}

// show invert state for "cat invert"
static ssize_t led_invert_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
    struct led_classdev *led_cdev = dev_get_drvdata(dev);
    struct oneshot_trig_data *oneshot_data = led_cdev->trigger_data;

    return sprintf(buf, "%u\n", oneshot_data->invert);
}

// set invert from sysfs write to invert file (e.g. echo 1 > invert)
static ssize_t led_invert_store(struct device *dev,
        struct device_attribute *attr, const char *buf, size_t size)
{
    struct led_classdev *led_cdev = dev_get_drvdata(dev);
    struct oneshot_trig_data *oneshot_data = led_cdev->trigger_data;
    unsigned long state;
    int ret;

    ret = kstrtoul(buf, 0, &state);
    if (ret)
        return ret;

    oneshot_data->invert = !!state;

    if (oneshot_data->invert)
        led_set_brightness_async(led_cdev, LED_FULL);
    else
        led_set_brightness_async(led_cdev, LED_OFF);

    return size;
}

// show delay_on state for "cat delay_on"
static ssize_t led_delay_on_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
    struct led_classdev *led_cdev = dev_get_drvdata(dev);

    return sprintf(buf, "%lu\n", led_cdev->blink_delay_on);
}

// set delay_on from sysfs write to delay_on file (e.g. echo 20 > delay_on)
static ssize_t led_delay_on_store(struct device *dev,
        struct device_attribute *attr, const char *buf, size_t size)
{
    struct led_classdev *led_cdev = dev_get_drvdata(dev);
    unsigned long state;
    int ret;

    ret = kstrtoul(buf, 0, &state);
    if (ret)
        return ret;

    led_cdev->blink_delay_on = state;

    return size;
}

// show delay_off state for "cat delay_off"
static ssize_t led_delay_off_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
    struct led_classdev *led_cdev = dev_get_drvdata(dev);

    return sprintf(buf, "%lu\n", led_cdev->blink_delay_off);
}

// set delay_off from sysfs write to delay_off file (e.g. echo 20 > delay_off)
static ssize_t led_delay_off_store(struct device *dev,
        struct device_attribute *attr, const char *buf, size_t size)
{
    struct led_classdev *led_cdev = dev_get_drvdata(dev);
    unsigned long state;
    int ret;

    ret = kstrtoul(buf, 0, &state);
    if (ret)
        return ret;

    led_cdev->blink_delay_off = state;

    return size;
}

// these are the "attribute" definitions -- one for each sysfs entry
// pointers to these show up in the above functions as the "attr" argument
static DEVICE_ATTR(delay_on, 0644, led_delay_on_show, led_delay_on_store);
static DEVICE_ATTR(delay_off, 0644, led_delay_off_show, led_delay_off_store);
static DEVICE_ATTR(invert, 0644, led_invert_show, led_invert_store);
static DEVICE_ATTR(shot, 0200, NULL, led_shot);

// activate the trigger device
static void oneshot_trig_activate(struct led_classdev *led_cdev)
{
    struct oneshot_trig_data *oneshot_data;
    int rc;

    // create an instance of the private data we need
    oneshot_data = kzalloc(sizeof(*oneshot_data), GFP_KERNEL);
    if (!oneshot_data)
        return;

    // save the pointer in the led class struct so it's available to other
    // functions above
    led_cdev->trigger_data = oneshot_data;

    // attach the sysfs entries
    rc = device_create_file(led_cdev->dev, &dev_attr_delay_on);
    if (rc)
        goto err_out_trig_data;
    rc = device_create_file(led_cdev->dev, &dev_attr_delay_off);
    if (rc)
        goto err_out_delayon;
    rc = device_create_file(led_cdev->dev, &dev_attr_invert);
    if (rc)
        goto err_out_delayoff;
    rc = device_create_file(led_cdev->dev, &dev_attr_shot);
    if (rc)
        goto err_out_invert;

    // C: this is what the driver used to do
#if 0
    led_cdev->blink_delay_on = DEFAULT_DELAY;
    led_cdev->blink_delay_off = DEFAULT_DELAY;
#endif

    led_cdev->activated = true;

    // C: from here to the return is what the modified driver must do

#ifdef MYLED_USESTRUCT
    led_cdev->blink_delay_on = myled_init.delay_on;
    led_cdev->blink_delay_off = myled_init.delay_off;
    oneshot_data->invert = myled_init.invert;
#else
    led_cdev->blink_delay_on = myled_init_delay_on;
    led_cdev->blink_delay_off = myled_init_delay_off;
    oneshot_data->invert = myled_init_invert;
#endif

    // C: if invert is off, nothing to do -- just like before
    // if invert is set, we implement this as if we just got an instantaneous
    // write to the sysfs "invert" file (which would call led_invert_store
    // above)

    // C: this is a direct rip-off of the above led_invert_store function which
    // we can _not_ call here directly because we don't have access to the
    // data it needs for its arguments [at least, not conveniently]
    // so, we extract the one line we actually need
    if (oneshot_data->invert)
        led_set_brightness_async(led_cdev, LED_FULL);

    return;

    // release everything if an error occurs
err_out_invert:
    device_remove_file(led_cdev->dev, &dev_attr_invert);
err_out_delayoff:
    device_remove_file(led_cdev->dev, &dev_attr_delay_off);
err_out_delayon:
    device_remove_file(led_cdev->dev, &dev_attr_delay_on);
err_out_trig_data:
    kfree(led_cdev->trigger_data);
}

// deactivate the trigger device
static void oneshot_trig_deactivate(struct led_classdev *led_cdev)
{
    struct oneshot_trig_data *oneshot_data = led_cdev->trigger_data;

    // release/destroy all the sysfs entries [and free the private data]
    if (led_cdev->activated) {
        device_remove_file(led_cdev->dev, &dev_attr_delay_on);
        device_remove_file(led_cdev->dev, &dev_attr_delay_off);
        device_remove_file(led_cdev->dev, &dev_attr_invert);
        device_remove_file(led_cdev->dev, &dev_attr_shot);
        kfree(oneshot_data);
        led_cdev->activated = false;
    }

    /* Stop blinking */
    led_set_brightness(led_cdev, LED_OFF);
}

// definition/control for trigger device registration
// C: changed the name to "myled_oneshot"
static struct led_trigger oneshot_led_trigger = {
    .name     = "myled_oneshot",
    .activate = oneshot_trig_activate,
    .deactivate = oneshot_trig_deactivate,
};

// module init function -- register the trigger device
static int __init oneshot_trig_init(void)
{
    return led_trigger_register(&oneshot_led_trigger);
}

// module exit function -- unregister the trigger device
static void __exit oneshot_trig_exit(void)
{
    led_trigger_unregister(&oneshot_led_trigger);
}

module_init(oneshot_trig_init);
module_exit(oneshot_trig_exit);

MODULE_AUTHOR("Fabio Baltieri <fabio.baltieri@gmail.com>");
MODULE_DESCRIPTION("One-shot LED trigger");
MODULE_LICENSE("GPL");