一、篇头
- 本章介绍LED子系统的使用。
- 使用LED子系统,可以轻松实现对LED,例如常见的闪烁和亮度控制功能。
- 简单起见,本章先使用GPIO实现,在不模拟PWM的情况下,只能实现点亮和灭灯的效果,重点是介绍GPIO、LED子系统的使用。
本文基于Amlogic T972 , Android 9.0, 内核版本 4.9.113
二、系列文章
第1篇:基于Amlogic 安卓9.0, 驱动简说(一):字符设备驱动,手动创建设备
第2篇:基于Amlogic 安卓9.0, 驱动简说(二):字符设备驱动,自动创建设备
第3篇:基于Amlogic 安卓9.0, 驱动简说(三):使用misc框架,让驱动更简单
第4篇:基于Amlogic 安卓9.0, 驱动简说(四):Platform平台驱动,驱动与设备的分离
第5篇:基于Amlogic 安卓9.0, 驱动简说(五):基于GPIO、LED子系统的LED驱动
三、准备工作
3.1 原理图:挑选测试用GPIO脚
(1) 红色LED: GPIOZ_6
(2) 绿色LED: GPIOZ_2
(3) 黄色LED: GPIOZ_1
(4) GND接地
3.2 LED模块
• 如下4个PIN脚,分别连接至开发板的4个引脚
四、源码解析
4.1 DTS设备树
aml_led_class{
status = "okay";
compatible = "szhou,aml_led_class";
/*
* (1) amlled-gpios 是使用新版GPIO子系统API的固定写法,必须以 -gpios 结尾
* (2) “&gpio” : 引用的GPIO控制器的名称
* (3) “GPIOZ_X ” :是一个宏定义,可转换成具体的gpio index
* (4) 最后的GPIO_ACTIVE_HIGH,代表此PIN脚物理上是高电平有效
*/
amlled-gpios = <&gpio GPIOZ_6 GPIO_ACTIVE_HIGH>, //red_led
<&gpio GPIOZ_2 GPIO_ACTIVE_HIGH>, //green_led
<&gpio GPIOZ_1 GPIO_ACTIVE_HIGH>; //yellow_led
};
4.2 驱动源码
如下是驱动源码,已添加详细解释
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/leds.h> /* 包含 struct led_classdev 结构体,及API*/
#include <linux/gpio/consumer.h> /* 包含新版本GPIO子系统: -gpiod- API*/
/*
*
私有结构体, 可自行增加所需成员, 但必须包含 struct led_classdev
*/
struct led_dev
{
struct led_classdev cdev;
struct gpio_desc *desc;
};
static char *name_red = "red";
static char *name_green = "green";
static char *name_yellow = "yellow";
static struct led_dev *led_device[3];
/*
* (1)对 /sys/class/leds/red/brightness 等LED属性进行控制时,会回调此函数
*/
static void led_control(struct led_classdev *led_cdev, enum led_brightness brightness)
{
struct led_dev *led = container_of(led_cdev, struct led_dev, cdev);
pr_info(" ENTER led_control led(0x%p)->desc=0x%p \n", led, led->desc);
//根据设定,设置亮或灭
if (brightness != LED_OFF) {
gpiod_set_value(led->desc , 1);
pr_info(" gpiod_set_value(led->desc , 1) \n");
}else{
gpiod_set_value(led->desc , 0);
pr_info(" gpiod_set_value(led->desc , 0) \n");
}
pr_info("EXIT led_control \n");
}
/*
* (1)在检测到DT中.compatible = "szhou,aml_led_class"的节点后,会自动调用此函数,实现初始化
*/
static int __init ledclass_plat_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
int i, count, ret;
pr_info( "ledclass_plat_probe enter\n");
/* 获取amlled-gpios里面gpio的数量 */
count = gpiod_count(dev, "amlled");
if (count == -ENOENT)
return -ENOENT;
dev_info(dev, "gpiod_count = %d \n", count);
/* 填充每个gpio-led对象,并注册到LED子系统 */
for(i=0; i<count; i++){
//struct led_dev *led_device;
//struct gpio_desc *desc = NULL;
led_device[i] = devm_kzalloc(dev, sizeof(struct led_dev), GFP_KERNEL);
if (!led_device[i])
return -ENOMEM;
/* 申请并初始化gpio描述符,电平初始化为GPIOD_OUT_LOW,即设为输出脚、低电平 */
led_device[i]->desc = gpiod_get_index(dev, "amlled", i, GPIOD_OUT_LOW);
pr_info(" ledclass_plat_probe led(0x%p)->desc=0x%p \n", led_device[i], led_device[i]->desc);
switch(i){
case 0:
led_device[0]->cdev.name = name_red;
pr_info("zs, 000000000 \n");
//led_device->cdev.default_trigger = "heartbeat";//红灯将使用默认的闪烁程序,若启用,则要添加类似互斥锁
break;
case 1:
led_device[1]->cdev.name = name_green;
pr_info("zs, 111111111111111 \n");
break;
case 2:
led_device[2]->cdev.name = name_yellow;
pr_info("zs, 22222222222 \n");
break;
default:
pr_info( "zs, i=%d, default \n", i);
}
pr_info("zs, 33333333333333 \n");
/* 初始化亮度值,以及LED的控制函数 */
led_device[i]->cdev.brightness = LED_OFF;
led_device[i]->cdev.brightness_set = led_control;
/* 注册到LED子系统 */
ret = devm_led_classdev_register(dev, &led_device[i]->cdev);
pr_info( "zs, platform_probe devm_led_classdev_register [%d], cdev->name=%s \n", i, led_device[i]->cdev.name);
if (ret) {
dev_err(dev, "failed to register the led %s\n", led_device[i]->cdev.name);
return ret;
}
}
dev_info(dev, "ledclass_plat_probe exit\n");
return 0;
}
static int __exit ledclass_plat_remove(struct platform_device *pdev)
{
int i=0;
dev_info(&pdev->dev, "ledclass_plat_remove enter\n");
for(i=0; i<3; i++)
{
gpiod_put(led_device[i]->desc); //释放GPIO描述符
}
dev_info(&pdev->dev, "ledclass_plat_remove exit\n");
return 0;
}
/*
* 设备树的匹配属性 .compatible ,需完全相同才会匹配
*/
static const struct of_device_id my_of_ids[] = {
{
.compatible = "szhou,aml_led_class"},
{
},
};
MODULE_DEVICE_TABLE(of, my_of_ids);
/*
* led_platform_driver 结构体
*/
static struct platform_driver led_platform_driver = {
.probe = ledclass_plat_probe,
.remove = ledclass_plat_remove,
.driver = {
.name = "aml_class_leds",
.of_match_table = my_of_ids,
.owner = THIS_MODULE,
}
};
/*
* 注册 led_platform_driver 结构体到Platform子系统
*/
static int aml_GpioLedClass_plat_init(void)
{
int ret_val;
pr_info("aml_GpioLedClass_plat_init enter\n");
ret_val = platform_driver_register(&led_platform_driver);
if (ret_val !=0){
pr_err("platform value returned %d\n", ret_val);
return ret_val;
}
pr_info("aml_GpioLedClass_plat_init exit\n");
return 0;
}
/*
* 从Platform子系统注销 led_platform_driver 结构体
*/
static void aml_GpioLedClass_plat_exit(void)
{
pr_info("aml_GpioLedClass_plat_exit enter\n");
platform_driver_unregister(&led_platform_driver);
pr_info("aml_GpioLedClass_plat_exit exit\n");
}
module_init(aml_GpioLedClass_plat_init);
module_exit(aml_GpioLedClass_plat_exit);
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("szhou <66176468@qq.com>");
MODULE_DESCRIPTION("simple say[5]: led-class device driver");
五、测试
(1)因为LED子系统自动为我们创建了用户接口,所以通过命令行就可以测试对LED的控制。
(2)编译、部署方法,参考之前的系列文章,不再赘述
5.1 加载KO
执行打印:
:/sys/class/leds # insmod /data/aml_gpio_led_class_platform.ko
[ 2647.823967@3]- aml_GpioLedClass_plat_init enter
[ 2647.824465@3]- ledclass_plat_probe enter
[ 2647.826870@3]- aml_class_leds aml_led_class: gpiod_count = 3
[ 2647.832558@3]- ledclass_plat_probe led(0xe9c8c110)->desc=0xed96b860
[ 2647.839026@3]- zs, 000000000
[ 2647.842103@3]- zs, 33333333333333
[ 2647.846052@3]- zs, platform_probe devm_led_classdev_register [0], cdev->name=red
[ 2647.853321@3]- ledclass_plat_probe led(0xe9c8c410)->desc=0xed96b820
[ 2647.859739@3]- zs, 111111111111111
[ 2647.863350@3]- zs, 33333333333333
[ 2647.867275@3]- zs, platform_probe devm_led_classdev_register [1], cdev->name=green
[ 2647.874691@3]- ledclass_plat_probe led(0xe9c8c010)->desc=0xed96b810
[ 2647.881132@3]- zs, 22222222222
[ 2647.884409@3]- zs, 33333333333333
[ 2647.888257@3]- zs, platform_probe devm_led_classdev_register [2], cdev->name=yellow
[ 2647.895792@3]- aml_class_leds aml_led_class: ledclass_plat_probe exit
[ 2647.902477@3]- aml_GpioLedClass_plat_init exit
:/sys/class/leds # echo 1 > red/brightness [ 2673.284925@0]- ENTER led_control led(0xe9c8c110)->desc=0xed96b860
[ 2673.285676@0]- gpiod_set_value(led->desc , 1)
[ 2673.290656@0]- EXIT led_control
图示如下:
![在这里插入图片描述](https://ucc.alicdn.com/images/user-upload-01/0b508175afbe4d4e88cededed4a28a75.png
5.2 查看设备
如下可见到在probe里面命名的3个LED灯,分别是red、green、yellow
执行打印:
x301:/ # cd /sys/class/leds/
x301:/sys/class/leds # ls -al
total 0
drwxr-xr-x 2 root root 0 2023-01-05 01:16 .
drwxr-xr-x 131 root root 0 2023-01-05 01:16 ..
lrwxrwxrwx 1 root root 0 2023-01-05 01:38 green -> ../../devices/platform/aml_led_class/leds/green
lrwxrwxrwx 1 root root 0 2023-01-05 01:38 pwm_e1 -> ../../devices/platform/pwmleds/leds/pwm_e1
lrwxrwxrwx 1 root root 0 2023-01-05 01:38 red -> ../../devices/platform/aml_led_class/leds/red
lrwxrwxrwx 1 root root 0 2023-01-05 01:38 yellow -> ../../devices/platform/aml_led_class/leds/yellow
x301:/sys/class/leds #
图示如下:
5.3 LED控制
(1)查看LED灯的属性,例如red
x301:/sys/class/leds # cd red/
x301:/sys/class/leds/red # ls -al
total 0
drwxr-xr-x 3 root root 0 2023-01-05 01:33 .
drwxr-xr-x 5 root root 0 2023-01-05 01:33 ..
-rw-r--r-- 1 root root 4096 2023-01-05 01:41 brightness
lrwxrwxrwx 1 root root 0 2023-01-05 01:41 device -> ../../../aml_led_class
-r--r--r-- 1 root root 4096 2023-01-05 01:41 max_brightness
drwxr-xr-x 2 root root 0 2023-01-05 01:41 power
lrwxrwxrwx 1 root root 0 2023-01-05 01:41 subsystem -> ../../../../../class/leds
-rw-r--r-- 1 root root 4096 2023-01-05 01:41 trigger
-rw-r--r-- 1 root root 4096 2023-01-05 01:41 uevent
(2)可见red默认为0,灯灭,符合设定
x301:/sys/class/leds/red # cat brightness
0
(3)点亮红灯
x301:/sys/class/leds/red # echo 1 > brightness
x301:/sys/class/leds/red # cd ..
(4)点亮绿灯
127|x301:/sys/class/leds # echo 1 > green/brightness
(5)点亮黄灯
x301:/sys/class/leds # echo 1 > yellow/brightness
x301:/sys/class/leds #
命令图示如下:
5.4 点灯效果
六、源码下载
git clone git@gitee.com:amizhou/amlogic_t972_android9_driver.git
七、篇尾
保持持续学习, 欢迎交流。