字符设备驱动（1）驱动代码完整源码：charButtons.c

2025-01-09 来源：cnblogs

内核版本：Linux3.0.8

开发板：基于三星S5PV210处理器的Tiny210开发板

驱动名称：charButtons.c

驱动描述：按键触发中断，中断处理程序执行相应的简单LED点亮操作

方案1注册字符设备使用新的接口实现（需要好几个函数来实现。貌似更复杂）

方案2注册字符设备使用老的接口实现（貌似老接口更简单）

/*****************************************************************************

简述：简单字符型驱动程序，手动静态分配设备号，手动创建设备节点

******************************************************************************/

#include

#define DEVICE_NAME 'buttons'

struct button_desc {

int gpio;

int number;

char *name;

};

struct led_desc {

int gpio;

int number;

char *name;

};

static struct button_desc buttons[] = {

{ S5PV210_GPH2(0), 0, 'KEY0' },

{ S5PV210_GPH2(1), 1, 'KEY1' },

{ S5PV210_GPH2(2), 2, 'KEY2' },

{ S5PV210_GPH2(3), 3, 'KEY3' },

{ S5PV210_GPH3(0), 4, 'KEY4' },

{ S5PV210_GPH3(1), 5, 'KEY5' },

{ S5PV210_GPH3(2), 6, 'KEY6' },

{ S5PV210_GPH3(3), 7, 'KEY7' },

};

static struct led_desc leds[] = {

{S5PV210_GPJ2(0),1,'LED1'},

{S5PV210_GPJ2(1),2,'LED2'},

{S5PV210_GPJ2(2),3,'LED3'},

{S5PV210_GPJ2(3),4,'LED4'},

};

#define OK (0)

#define ERROR (-1)

struct gpio_chip *chip;

struct cdev *gDev;

struct file_operations *gFile;

dev_t devNum;

unsigned int subDevNum = 1;//要申请的次设备号个数

int reg_major = 234;

int reg_minor = 0;

static irqreturn_t button_interrupt(int irq, void *dev_id)

{

struct button_desc *bdata = (struct button_desc *)dev_id;

int down;

unsigned tmp;

tmp = gpio_get_value(bdata->gpio);

/* active low */

down = !tmp;

printk('KEY %d: %08xn', bdata->number, down);

if(bdata->number < 4)

{

gpio_set_value(leds[bdata->number].gpio,0);

printk('LED %d: On n',leds[bdata->number].number);

}

else

{

gpio_set_value(leds[(bdata->number) - 4].gpio,1);

printk('LED %d: OFF n',leds[(bdata->number)-4].number);

}

return IRQ_HANDLED;

}

int butsOpen(struct inode *p, struct file *f)

{

int irq;

int i;

int err = 0;

printk(KERN_EMERG'butsOpenrn');

for (i = 0; i < ARRAY_SIZE(buttons); i++) {

if (!buttons[i].gpio)

continue;

irq = gpio_to_irq(buttons[i].gpio);

// irq = IRQ_EINT(16)+i =160+i 'S5PV210_GPH2(i)'

//irq = IRQ_EINT(24)+i =168+i 'S5PV210_GPH3(i)'

err = request_irq(irq, button_interrupt, IRQ_TYPE_EDGE_BOTH,

buttons[i].name, (void *)&buttons[i]);

if (err)

break;

}

for(i = 0; i {

if(!leds[i].gpio)

continue;

gpio_direction_output(leds[i].gpio,1);

}

if (err) {

i--;

for (; i >= 0; i--) {

if (!buttons[i].gpio)

continue;

irq = gpio_to_irq(buttons[i].gpio);

disable_irq(irq);

free_irq(irq, (void *)&buttons[i]);

}

return -EBUSY;

}

return 0;

}

int charDrvInit(void)

{

devNum = MKDEV(reg_major, reg_minor);

printk(KERN_EMERG'devNum is %drn', devNum);

if(OK == register_chrdev_region(devNum, subDevNum, DEVICE_NAME))

{

printk(KERN_EMERG'register_chrdev_region okrn');

}

else

{

printk(KERN_EMERG'register_chrdev_region errorrn');

return ERROR;

}

/*if(OK == alloc_chrdev_region(&devNum, subDevNum, subDevNum,'test'))

{

printk(KERN_EMERG'register_chrdev_region okrn');

}

else

{

printk(KERN_EMERG'register_chrdev_region errorrn');

return ERROR;

}*/

gDev = kzalloc(sizeof(struct cdev), GFP_KERNEL);

gFile = kzalloc(sizeof(struct file_operations), GFP_KERNEL);

gFile->open = butsOpen;

//注册设备函数到file_operations结构体gFile

//gDev->owner = THIS_MODULE;

gFile->owner = THIS_MODULE;

cdev_init(gDev, gFile);

//在cdev结构体中添加指针指向file_operations结构体gFile

cdev_add(gDev, devNum, 3);

//建立设备号与cdev结构体联系

printk(KERN_EMERG'button driver initial done...rn');

return 0;

}

void __exit charDrvExit(void)

{

int i,irq;

cdev_del(gDev);

unregister_chrdev_region(devNum, subDevNum);

for (i = 0; i < ARRAY_SIZE(buttons); i++) {

if (!buttons[i].gpio)

continue;

irq = gpio_to_irq(buttons[i].gpio);

disable_irq(irq);

free_irq(irq, (void *)&buttons[i]);

}

return;

}

module_init(charDrvInit);//执行insmod时会执行此行代码并调用charDrvInit，驱动开始

module_exit(charDrvExit);//执行rmmod时，结束

MODULE_LICENSE('GPL');

/*****************************************************************************

简述：简单字符型驱动程序，手动静态分配设备号，手动创建设备节点

******************************************************************************/

#include

#define DEVICE_NAME 'leds'

struct button_desc {

int gpio;

int number;

char *name;

};

struct led_desc {

int gpio;

int number;

char *name;

};

static struct button_desc buttons[] = {

{ S5PV210_GPH2(0), 0, 'KEY0' },

{ S5PV210_GPH2(1), 1, 'KEY1' },

{ S5PV210_GPH2(2), 2, 'KEY2' },

{ S5PV210_GPH2(3), 3, 'KEY3' },

{ S5PV210_GPH3(0), 4, 'KEY4' },

{ S5PV210_GPH3(1), 5, 'KEY5' },

{ S5PV210_GPH3(2), 6, 'KEY6' },

{ S5PV210_GPH3(3), 7, 'KEY7' },

};

static struct led_desc leds[] = {

{S5PV210_GPJ2(0),1,'LED1'},

{S5PV210_GPJ2(1),2,'LED2'},

{S5PV210_GPJ2(2),3,'LED3'},

{S5PV210_GPJ2(3),4,'LED4'},

};

#define OK (0)

#define ERROR (-1)

dev_t devNum;

unsigned int subDevNum = 1;//要申请的次设备号个数

int reg_major = 234;

int reg_minor = 0;

static irqreturn_t button_interrupt(int irq, void *dev_id)

{

struct button_desc *bdata = (struct button_desc *)dev_id;

int down;

unsigned tmp;

tmp = gpio_get_value(bdata->gpio);

/* active low */

down = !tmp;

printk('KEY %d: %08xn', bdata->number, down);

if(bdata->number < 4)

{

gpio_set_value(leds[bdata->number].gpio,0);

printk('LED %d: On n',leds[bdata->number].number);

}

else

{

gpio_set_value(leds[(bdata->number) - 4].gpio,1);

printk('LED %d: OFF n',leds[(bdata->number)-4].number);

}

return IRQ_HANDLED;

}

int butsOpen(struct inode *p, struct file *f)

{

int irq;

int i;

int err = 0;

printk(KERN_EMERG'butsOpenrn');

for (i = 0; i < ARRAY_SIZE(buttons); i++) {

if (!buttons[i].gpio)

continue;

irq = gpio_to_irq(buttons[i].gpio);

// irq = IRQ_EINT(16)+i =160+i 'S5PV210_GPH2(i)'

//irq = IRQ_EINT(24)+i =168+i 'S5PV210_GPH3(i)'

err = request_irq(irq, button_interrupt, IRQ_TYPE_EDGE_FALLING,

buttons[i].name, (void *)&buttons[i]);

if (err)

break;

}

for(i = 0; i {

if(!leds[i].gpio)

continue;

gpio_direction_output(leds[i].gpio,1);

}

if (err) {

i--;

for (; i >= 0; i--) {

if (!buttons[i].gpio)

continue;

irq = gpio_to_irq(buttons[i].gpio);

disable_irq(irq);

free_irq(irq, (void *)&buttons[i]);

}

return -EBUSY;

}

return 0;

}

static const struct file_operations gFile =

{

.owner = THIS_MODULE,

.open = butsOpen,

};

int charDrvInit(void)

{

devNum = MKDEV(reg_major, reg_minor);

printk(KERN_EMERG'devNum is %drn', devNum);

if(OK == register_chrdev(reg_major, DEVICE_NAME, &gFile))

{

printk(KERN_EMERG 'register_chrdev_region okrn');

}

else

{

printk(KERN_EMERG'register_chrdev_region errorrn');

return ERROR;

}

printk(KERN_EMERG 'button driver initial done...rn');

return 0;

}

void __exit charDrvExit(void)

{

int i,irq;

unregister_chrdev(reg_major, DEVICE_NAME);

for (i = 0; i < ARRAY_SIZE(buttons); i++) {

if (!buttons[i].gpio)

continue;

irq = gpio_to_irq(buttons[i].gpio);

disable_irq(irq);

free_irq(irq, (void *)&buttons[i]);

}

return;

}

module_init(charDrvInit);//执行insmod时会执行此行代码并调用charDrvInit，驱动开始

module_exit(charDrvExit);//执行rmmod时，结束

MODULE_LICENSE('GPL');

MODULE_AUTHOR('LiuB');

函数修饰符

__init，本质上是一个宏定义，在内核源代码中定义：#define __init __section(.init.text) __cold notrace

作用就是，将被它修饰的函数放入.init.text段中去。所以所有的内核模块的__init修饰的函数被放在一起。内核启动时统一加载，加载完后统一释放以节省内存。

__exit,同上：#define __exit __section(.exit.text) __exitused __cold notrace

printk()函数：内核封装出来的打印函数。格式:

printk( 打印级别 “打印信息”) //printk的打印级别是用来控制printk打印的信息是否在终端显示

#define KERN_EMERG '<0>' /* system is unusable */

#define KERN_ALERT '<1>' /* action must be taken immediately */

#define KERN_CRIT '<2>' /* critical conditions */

#define KERN_ERR '<3>' /* error conditions */

#define KERN_WARNING '<4>' /* warning conditions */

#define KERN_NOTICE '<5>' /* normal but significant condition */

#define KERN_INFO '<6>' /* informational */

#define KERN_DEBUG '<7>' /* debug-level messages */

/* Use the default kernel loglevel */

#define KERN_DEFAULT ''

如果定义了模块，即这一驱动被动态编译为模块时

驱动代码中的module_init、module_exit的内核定义（/include/linux/init.h）

/* Each module must use one module_init(). */

#define module_init(initfn)

static inline initcall_t __inittest(void) { return initfn; }

int init_module(void) __attribute__((alias(#initfn)));

typedef int (*initcall_t)(void);

//static inline initcall_t __inittest(void) { return initfn; }

//inittest这个函数返回值为一个initcall_t类型的initfn

//而initcall_t是一个函数指针，返回值为整型，输入参数为空

/* This is only required if you want to be unloadable. */

#define module_exit(exitfn)

static inline exitcall_t __exittest(void) { return exitfn; }

void cleanup_module(void) __attribute__((alias(#exitfn)));

typedef void (*exitcall_t)(void);

如果未定义模块，这一驱动被静态编译进内核

驱动代码中的module_init、module_exit的内核定义（/include/linux/init.h）

/**

* module_init() - driver initialization entry point

* @x: function to be run at kernel boot time or module insertion

* module_init() will either be called during do_initcalls() (if

* builtin) or at module insertion time (if a module). There can only

* be one per module.

#define module_init(x) __initcall(x);

#define __initcall(fn) device_initcall(fn)

#define device_initcall(fn) __define_initcall('6',fn,6)

/* initcalls are now grouped by functionality into separate

* subsections. Ordering inside the subsections is determined

* by link order.

* For backwards compatibility, initcall() puts the call in

* the device init subsection.

* The `id' arg to __define_initcall() is needed so that multiple initcalls

* can point at the same handler without causing duplicate-symbol build errors.

#define __define_initcall(level,fn,id)

static initcall_t __initcall_##fn##id __used

__attribute__((__section__('.initcall' level '.init'))) = fn

通过这些段代码，我们能够看出最终的结果是将我们使用module_init修饰的函数指针链接到一个叫.initcall的段里，也就是说最终所有使用module_init修饰的函数指针都被链接在这个段里，内核在启动的时候顺序调用所有链接在这个段里的函数，实现设备的初始化

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字符设备驱动驱动代码 charButtons c

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