iTOP4412设备驱动学习七--LEDS驱动

资源来源于迅为视频学习教程。

本节是LEDS驱动的调用学习，根据之前的学习的杂项设备的基础上实现驱动LED2的亮灭。

1.LED原理图使用了三极管，首先三极管的了解：

我们这个是NPN鍺管

三极管：电流控制电源(模电术语)。理解起来：电流指1->2之间的电流。内部构造较为复杂。有时间再学习补充。

理解：2和3之间有一个可调电阻，其大小由1过来的电流决定。当左边低电平电流小，电阻无穷大。当左边高电平时电流大，电阻值变小，则LED2有电阻电压差，可以发亮。

2. LED相关头文件

    Linux中申请GPIO的头文件(各平台通用)：include/linux/gpio.h  如函数gpio_request等

    三星平台的GPIO配置函数头文件，宏定义头文件：arch/arm/plat-samsung/include/plat/gpio-cfg.h  包括三星所有板子配置函数

    三星平台EXYNOS系列平台，GPIO配置参数宏定义头文件：arch/arm/mach-exynos/include/mach/gpio.h  GPIO管脚拉高拉低配置参数等等

    三星平台4412平台，GPIO宏定义头文件：arch/arm/mach-exynos/include/mach/gpio-exynos4.h  已经包含在头文件gpio.h中，包括4412处理器所有GPIO的宏定义。

3. LED函数

    Linux的GPIO中申请函数和赋值函数：gpio_request，gpio_set_value

    三星平台配置GPIO函数：s3c_gpio_cfgpin

    GPIO配置输出模式的宏变量：s3c_GPIO_OUTPUT

4.函数在内核中的实现定义方法

    函数gpio_request，gpio_set_value

include/linux/gpio.h 
//参数1是GPIO的宏，参数2是提高可读性的，可直接指定一个字符串
 44 static inline int gpio_request(unsigned gpio, const char *label)
 45 {
 46         return -ENOSYS;
 47 }
 98 static inline void gpio_set_value(unsigned gpio, int value)
 99 {
100         /* GPIO can never have been requested or set as output */
101         WARN_ON(1);
102 }

arch/arm/plat-samsung/include/plat/gpio-cfg.h
 77 /**
 78  * s3c_gpio_cfgpin() - Change the GPIO function of a pin.
 79  * @pin pin The pin number to configure.
 80  * @to to The configuration for the pin's function.
 81  *
 82  * Configure which function is actually connected to the external
 83  * pin, such as an gpio input, output or some form of special function
 84  * connected to an internal peripheral block.
 85  *
 86  * The @to parameter can be one of the generic S3C_GPIO_INPUT, S3C_GPIO_OUTPUT
 87  * or S3C_GPIO_SFN() to indicate one of the possible values that the helper
 88  * will then generate the correct bit mask and shift for the configuration.
 89  *
 90  * If a bank of GPIOs all needs to be set to special-function 2, then
 91  * the following code will work:
 92  *
 93  *      for (gpio = start; gpio < end; gpio++)
 94  *              s3c_gpio_cfgpin(gpio, S3C_GPIO_SFN(2));
 95  *
 96  * The @to parameter can also be a specific value already shifted to the
 97  * correct position in the control register, although these are discouraged
 98  * in newer kernels and are only being kept for compatibility.
 99  */
100 extern int s3c_gpio_cfgpin(unsigned int pin, unsigned int to);    //参数1是GPIO宏，参数2要将其配置为什么样的GPIO,使用宏S3C_GPIO_OUTPUT

arch/arm/plat-samsung/include/plat/gpio-cfg.h
 69 /* Defines for generic pin configurations */
 70 #define S3C_GPIO_INPUT  (S3C_GPIO_SPECIAL(0))
 71 #define S3C_GPIO_OUTPUT (S3C_GPIO_SPECIAL(1))          //这个是输出模式的宏变量
 72 #define S3C_GPIO_SFN(x) (S3C_GPIO_SPECIAL(x))

因为系统提供的config中默认是将LEDS打开的，所以我们需要重巡编译内核，去掉LEDS驱动，然后加载我们自己写的LEDS驱动。

4. 修改config重新编译：

 首先修改config，将LED配置关闭

$ make menuconfig

scripts/kconfig/mconf Kconfig
#
# configuration written to .config
#


*** End of the configuration.
*** Execute 'make' to start the build or try 'make help'.

$ make zImage -j4
...
  OBJCOPY arch/arm/boot/Image
  Kernel: arch/arm/boot/Image is ready
  GZIP    arch/arm/boot/compressed/piggy.gzip
  SHIPPED arch/arm/boot/compressed/lib1funcs.S
  AS      arch/arm/boot/compressed/lib1funcs.o
  AS      arch/arm/boot/compressed/piggy.gzip.o
  LD      arch/arm/boot/compressed/vmlinux
  OBJCOPY arch/arm/boot/zImage
  Kernel: arch/arm/boot/zImage is ready

将新的zImage烧写到板子中，烧写方法同之前操作。

5.LEDS驱动代码：

此代码与上次相比增加了hello_pobe和hello_ioctl中的调用。

leds驱动源码leds.c：

#include <linux/init.h>
#include <linux/module.h>

#include <linux/platform_device.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>

#include <linux/gpio.h>  //通用的一般会被其他的包含
#include <plat/gpio-cfg.h> //三星平台
#include <mach/gpio.h>  //EXYNOS平台
#include <mach/gpio-exynos4.h>  //4412平台

#define DRIVER_NAME "hello_ctl"
#define DEVICE_NAME "hello_ctl"

//参数1是GPIO的值为0或1，参数2是GPIO的个数
static long hello_ctl(struct file *files, unsigned int cmd, unsigned long arg){
    printk(KERN_EMERG "cmd is %d, args is %d
", cmd, arg);
    if(cmd > 1){
        printk(KERN_EMERG "ERROR: cmd is 0 or 1
");
    }
    if(arg > 1){
        printk(KERN_EMERG "ERROR: arg is only 1
");
    }
    gpio_set_value(EXYNOS4_GPL2(0), cmd);
    return 0;
}
static int hello_release(struct inode *inode, struct file *file){
    printk(KERN_EMERG "hello release!
");
    return 0;
}
static int hello_open(struct inode *inode,  struct file *file){
    printk(KERN_EMERG "hello open
");
    return 0;
}
static struct file_operations hello_ops = {
    .owner = THIS_MODULE,
    .open = hello_open,
    .release = hello_release,
    .unlocked_ioctl = hello_ctl,
};

static struct miscdevice hello_dev = {
    .minor = MISC_DYNAMIC_MINOR,
    .name = DEVICE_NAME,
    .fops = &hello_ops,
};

//资源申请也在probe中
static int hello_probe(struct platform_device *pdv){
    int ret;
    printk(KERN_EMERG "initialized
");

    ret = gpio_request(EXYNOS4_GPL2(0), "LEDS");    //参数宏在文件中查找：arch/arm/mach-exynos/include/mach/gpio-exynos4.h
    if(ret < 0){
        printk(KERN_EMERG "gpio_request EXYNOS4_GPL2(0) failed
");
        return ret;
    }

    s3c_gpio_cfgpin(EXYNOS4_GPL2(0), S3C_GPIO_OUTPUT);

    gpio_set_value(EXYNOS4_GPL2(0), 0);

    misc_register(&hello_dev);
    return 0;
}
static int hello_remove(struct platform_device *pdv){
    printk(KERN_EMERG "remove
");
    misc_deregister(&hello_dev);
    return 0;
}
static void hello_shutdown(struct platform_device *pdev){
    ;
}
static int hello_suspend(struct platform_device *pdv, pm_message_t pmt){
    return 0;
}
static int hello_resume(struct platform_device *pdv){
    return 0;
}

struct platform_driver hello_driver = {
    .probe = hello_probe,
    .remove = hello_remove,
    .shutdown = hello_shutdown,
    .suspend = hello_suspend,
    .resume = hello_resume,
    .driver = {
        .name = DRIVER_NAME,
        .owner = THIS_MODULE,
    }
};

static int hello_init(void){
    int DriverState;

    printk(KERN_EMERG "hello world enter!
");
    DriverState = platform_driver_register(&hello_driver);

    printk(KERN_EMERG "DriverState is %d
", DriverState);
    return 0;
}

static void hello_exit(void){
    printk(KERN_EMERG "hello world exit!
");
    platform_driver_unregister(&hello_driver);
}

module_init(hello_init);
module_exit(hello_exit);

MODULE_LICENSE("Dual BSD/GPL");

Makefile

obj-m += leds.o

KDIR := /home/nan/iTOP4412/iTop4412_Kernel_3.0

PWD ?= $(shell pwd)

all:
    make -C $(KDIR) M=$(PWD) modules
clean:
    rm -rf *.o

上层调用invoke_leds.c：

#include <stdio.h>
#include <sys/type.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>

int main()
{
    int fd;
    char *hello_node = "/dev/hello_ctl"

    if((fd = open(hello_node, O_RDWR|O_NDELAY)) < 0){
        printf("App open %s failed!
", hello_node);
    }
    else{
        printf("App open %s success
", hello_node);
        ioctl(fd, 1, 1);   //1:cmd 2:arg
        sleep(3);
        ioctl(fd, 0, 1);
        sleep(3);
        ioctl(fd, 1, 1);
    }
    close(fd);

    return 0;
}

然后编译：

nan@nanzh:~/iTOP4412/7$ make
make -C /home/nan/iTOP4412/iTop4412_Kernel_3.0 M=/home/nan/iTOP4412/7 modules
make[1]: Entering directory '/home/nan/iTOP4412/iTop4412_Kernel_3.0'
  CC [M]  /home/nan/iTOP4412/7/leds.o
/home/nan/iTOP4412/7/leds.c: In function 'hello_ctl':
/home/nan/iTOP4412/7/leds.c:18: warning: format '%d' expects type 'int', but argument 3 has type 'long unsigned int'
  Building modules, stage 2.
  MODPOST 1 modules
  CC      /home/nan/iTOP4412/7/leds.mod.o
  LD [M]  /home/nan/iTOP4412/7/leds.ko
make[1]: Leaving directory '/home/nan/iTOP4412/iTop4412_Kernel_3.0'

nan@nanzh:~/iTOP4412/7$ arm-none-linux-gnueabi-gcc invoke_leds.c -o invoke_leds -static
nan@nanzh:~/iTOP4412/7$ ls invoke_leds*
invoke_leds  invoke_leds.c

拷贝到板子上运行：

root@iTOP4412-ubuntu-desktop:~# cat /proc/modules 
root@iTOP4412-ubuntu-desktop:~# ls /dev/leds
ls: cannot access /dev/leds: No such file or directory
root@iTOP4412-ubuntu-desktop:~/tests/7# insmod leds.ko 
[  946.850211] hello world enter!
[  946.852131] initialized
[  946.875142] DriverState is 0
root@iTOP4412-ubuntu-desktop:~/tests/7# ./invoke_leds 
[  973.092455] hello open
[  973.093867] cmd is 1, args is 1
App open /dev/hello_ctl success
[  976.100390] cmd is 0, args is 1
[  979.102297] cmd is 1, args is 1
[  979.104001] hello release!
root@iTOP4412-ubuntu-desktop:~/tests/7# rmmod leds
[ 1078.413217] hello world exit!
[ 1078.414806] remove

板子上的现象就是边上LED2一开始是亮的，被uboot点亮，然后运行invoke_leds会灭了三秒再亮。

以上就是本节内容