編寫按鍵中斷驅動
- 硬件平臺:韋東山嵌入式Linxu開發板(S3C2440.v3)
- 軟件平臺:運行於VMware Workstation 12 Player下UbuntuLTS16.04_x64 系統
- 參考資料:《嵌入式Linux應用開發手冊》、《嵌入式Linux應用開發手冊第2版》
- 開發環境:Linux 2.6.22.6 內核、arm-linux-gcc-3.4.5-glibc-2.3.6工具鏈
目錄
編寫按鍵中斷驅動 - 一、程序框架圖
- 1、`request_irq()`註冊中斷服務函數解析
- 2、`free_irq()`函數解析
- 3、`wait_event_interruptible()`宏解析
- 4、`wake_up_interruptible()`宏解析
- 二、驅動文件編寫
- 1、定義的變量
- 2、告訴內核有這個驅動程序
- 2.1 構建` file_operations()`結構體
- 2.2 定義驅動的入口函數`button_drv_init()`、註冊驅動`register_chrdev()`
- 2.3 定義驅動的出口函數`button_drv_exit()`、卸載驅動`unregister_chrdev()`
- 2.4 修飾出、入口函數,讓內核怎麼知道哪個設備對應哪個的出、入口
- 3、編寫中斷服務函數`button_irq()`
- 4、編寫驅動函數
- 三、Makefile文件編寫
- 四、測試程序的編寫
- 五、實際運行
一、程序框架圖
1、request_irq()
註冊中斷服務函數解析
1.1 函數原型與作用
- 源碼處於:
\arch\arm26\kernel\irq.c
, - 作用:向內核註冊中斷,不需要像裸板驅動配置各種寄存器
int request_irq(unsigned int irq, irqreturn_t (*handler)(int, void *, struct pt_regs *),
unsigned long irq_flags, const char * devname, void *dev_id)
{
unsigned long retval;
struct irqaction *action;
if (irq >= NR_IRQS || !irq_desc[irq].valid || !handler ||
(irq_flags & IRQF_SHARED && !dev_id))
return -EINVAL;
action = kmalloc(sizeof(struct irqaction), GFP_KERNEL);
if (!action)
return -ENOMEM;
action->handler = handler;
action->flags = irq_flags;
cpus_clear(action->mask);
action->name = devname;
action->next = NULL;
action->dev_id = dev_id;
retval = setup_irq(irq, action);
if (retval)
kfree(action);
return retval;
}
1.2 參數講解
unsigned int irq
:申請的硬件中斷號,在Linux內核中,已有開發板的驅動中有對應的宏定義irqreturn_t (*handler)(int, void *, struct pt_regs *),
:系統註冊的中斷處理函數,自己編寫unsigned long irq_flags,
:中斷處理的屬性,如按鍵中斷中的上升沿觸發、下升沿觸發等,在Linux內核中,已有開發板的驅動中有對應的宏定義const char * devname,
:設置中斷名稱,通常是設備驅動程序的名稱,自己定義void *dev_id
:在中斷共享時會用到,傳入中斷處理程序的參數,註冊共享中斷時不能爲NULL,因爲卸載時需要這個做參數,避免卸載其它中斷服務函數,自己定義
1.3 返回值
函數運行正常時返回 0 ,否則返回對應錯誤的負值。
2、free_irq()
函數解析
2.1 函數原型與作用
- 源碼處於:
\arch\arm26\kernel\irq.c
, - 作用:向內核取消中斷,不需要像裸板驅動配置各種寄存器
void free_irq(unsigned int irq, void *dev_id)
{
struct irqaction * action, **p;
unsigned long flags;
if (irq >= NR_IRQS || !irq_desc[irq].valid) {
printk(KERN_ERR "Trying to free IRQ%d\n",irq);
#ifdef CONFIG_DEBUG_ERRORS
__backtrace();
#endif
return;
}
spin_lock_irqsave(&irq_controller_lock, flags);
for (p = &irq_desc[irq].action; (action = *p) != NULL; p = &action->next) {
if (action->dev_id != dev_id)
continue;
/* Found it - now free it */
*p = action->next;
kfree(action);
goto out;
}
printk(KERN_ERR "Trying to free free IRQ%d\n",irq);
#ifdef CONFIG_DEBUG_ERRORS
__backtrace();
#endif
out:
spin_unlock_irqrestore(&irq_controller_lock, flags);
}
2.2 參數講解
unsigned int irq
:申請的硬件中斷號,在Linux內核中,已有開發板的驅動中有對應的宏定義void *dev_id
:卸載的中斷action下的哪個服務函數*
3、wait_event_interruptible()
宏解析
3.1 宏原型
- 源碼處於:
\include\linux\wait.h
, - 作用:將本進程置爲可中斷的掛起狀態,反覆檢查condition是否成立,如果成立則退出,如果不成立則繼續休眠;條件滿足後,即把本進程運行狀態置爲運行態
#define wait_event_interruptible(wq, condition)
({
int __ret = 0;
if (!(condition))
__wait_event_interruptible(wq, condition, __ret);
__ret;
})
3.2 宏參數講解
- wq: 是一個等待隊列對頭的名字,名字也是通過下面這宏定義
#define DECLARE_WAIT_QUEUE_HEAD(name)
wait_queue_head_t name = __WAIT_QUEUE_HEAD_INITIALIZER(name)
- condition:是一個標誌位,爲0時休眠,爲1時喚醒
4、wake_up_interruptible()
宏解析
4.1 宏原型
- 源碼處於:
\include\linux\wait.h
, - 作用: // 喚醒休眠的進程
#define wake_up_interruptible(x) __wake_up(x, TASK_INTERRUPTIBLE, 1, NULL)
void fastcall __wake_up(wait_queue_head_t *q, unsigned int mode,
int nr_exclusive, void *key)
{
unsigned long flags;
spin_lock_irqsave(&q->lock, flags);
__wake_up_common(q, mode, nr_exclusive, 0, key);
spin_unlock_irqrestore(&q->lock, flags);
}
4.2 宏參數講解
- x:爲隊列名字,根據名字找到等待隊列,喚醒隊列所在的進程。
二、驅動文件編寫
1、定義的變量
int major;
static struct class *buttondrv_class;
static struct class_device *buttondrv_class_dev;
volatile unsigned long *gpfcon;
volatile unsigned long *gpfdat;
volatile unsigned long *gpgcon;
volatile unsigned long *gpgdat;
/* 鍵值: 按下時, 0x01, 0x02, 0x03, 0x04
* 鍵值: 鬆開時, 0x81, 0x82, 0x83, 0x84
*/
static unsigned char key_val;
/* 按鍵信息 */
struct pin_desc{
unsigned int pin;
unsigned int key_val;
};
/* 存儲4個按鍵的信息 */
struct pin_desc pins_desc[4] = {
{S3C2410_GPF0, 0x01},
{S3C2410_GPF2, 0x02},
{S3C2410_GPG3, 0x03},
{S3C2410_GPG11, 0x04},
};
/* 中斷註冊信息 */
struct buttonirq_decs{
unsigned int irq;
unsigned long flags;
const char *devname;
void *dev_id;
};
struct buttonirq_decs buttonirqs_decs[4] = {
{IRQ_EINT0, IRQT_BOTHEDGE, "S2", &pins_desc[0]},
{IRQ_EINT2, IRQT_BOTHEDGE, "S3", &pins_desc[1]},
{IRQ_EINT11, IRQT_BOTHEDGE, "S4", &pins_desc[2]},
{IRQ_EINT19, IRQT_BOTHEDGE, "S5", &pins_desc[3]},
};
/* 生成一個等待隊列的隊頭,名字爲button_waitq */
static DECLARE_WAIT_QUEUE_HEAD(button_waitq);
/* 中斷事件標誌, 中斷服務程序將它置1,button_drv_read將它清0 */
static volatile int ev_press = 0;
2、告訴內核有這個驅動程序
2.1 構建file_operations()
結構體
static struct file_operations button_drv_fops = {
.owner = THIS_MODULE, /* 這是一個宏,推向編譯模塊時自動創建的__this_module變量 */
.open = button_drv_open,
.read = button_drv_read,
.release = button_drv_close,
};
2.2 定義驅動的入口函數button_drv_init()
、註冊驅動register_chrdev()
/* 入口函數
* 執行”insmod button_drv.ko”命令時就會調用這個函數
*/
static int button_drv_init(void)
{
//註冊一個字符設備,名字爲button_drv
major = register_chrdev(0, "button_drv", &button_drv_fops);
//創建一個類,名字爲buttond_rv(/class/button_drv)
buttondrv_class = class_create(THIS_MODULE, "button_drv");
//創建一個設備節點,名爲button(/dev/button)
buttondrv_class_dev = class_device_create(buttondrv_class, NULL, MKDEV(major, 0), NULL, "button");
/* 映射物理地址 */
gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16);
gpfdat = gpfcon + 1;
gpgcon = (volatile unsigned long *)ioremap(0x56000060, 16);
gpgdat = gpgcon + 1;
return 0;
}
2.3 定義驅動的出口函數button_drv_exit()
、卸載驅動unregister_chrdev()
/* 出口函數
* 執行”rmmod button_drv.ko”命令時就會調用這個函數
*/
static void button_drv_exit(void)
{
unregister_chrdev(major, "button_drv"); // 卸載字符
class_device_unregister(buttondrv_class_dev); //刪除設備節點
class_destroy(buttondrv_class); //銷燬類
/* 取消映射 */
iounmap(gpfcon);
iounmap(gpgcon);
}
2.4 修飾出、入口函數,讓內核怎麼知道哪個設備對應哪個的出、入口
module_init(button_drv_init);
module_exit(button_drv_exit);
3、編寫中斷服務函數button_irq()
/* 中斷服務函數 */
static irqreturn_t button_irq(int irq, void *dev_id)
{
struct pin_desc *pindesc = (struct pin_desc *)dev_id;
unsigned int pinval;
pinval = s3c2410_gpio_getpin(pindesc->pin); //讀取IO口電平
if(pinval){
/* 鬆開 */
key_val = 0x80 | pindesc->key_val;
}else{
/* 按下 */
key_val = pindesc->key_val;
}
ev_press = 1; //發生中斷
wake_up_interruptible(&button_waitq); // 喚醒休眠的進程
return IRQ_RETVAL(IRQ_HANDLED);
}
4、編寫驅動函數
4.1 button_drv_open()
函數
* open驅動函數 */
static int button_drv_open(struct inode *inode, struct file *file)
{
unsigned int i;
int err;
/* 註冊中斷 */
for(i = 0; i < (sizeof(buttonirqs_decs)/sizeof(buttonirqs_decs[0])); i++){
err = request_irq(buttonirqs_decs[i].irq, button_irq, buttonirqs_decs[i].flags,
buttonirqs_decs[i].devname, buttonirqs_decs[i].dev_id);
if(err){
printk("func button_drv_open err: request_irq num:%d\n", i);
break;
}
}
/* 出現錯誤,釋放已經註冊的中斷 */
if(err){
i--;
for (; i >= 0; i--)
free_irq(buttonirqs_decs[i].irq, buttonirqs_decs[i].dev_id);
return -EBUSY;
}
return 0;
}
4.2 button_drv_read()
函數
/* read驅動函數 */
static ssize_t button_drv_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
{
unsigned long ret = 0;
int err;
/* 如果沒有按鍵動作, 休眠 */
err = wait_event_interruptible(button_waitq, ev_press);
if (err){
printk("func button_drv_read() err: wait_event_interruptible\n");
return err;
}
/* 如果有按鍵動作, 返回鍵值 */
ret = copy_to_user(buf, &key_val, 1);
ev_press = 0; //清中斷標誌
if(ret < 0){
printk("func button_drv_read() err: copy_to_user\n");
return -EFAULT;
}
return sizeof(key_val);
}
4.3 button_drv_close()
函數
/* close驅動函數 */
int button_drv_close (struct inode *inode, struct file *file)
{
int i;
/* 取消中斷 */
for(i = 0; i < (sizeof(buttonirqs_decs)/sizeof(buttonirqs_decs[0])); i++)
free_irq(buttonirqs_decs[i].irq, buttonirqs_decs[i].dev_id);
return 0;
}
三、Makefile文件編寫
KERN_DIR = /work/system/linux-2.6.22.6
all:
make -C $(KERN_DIR) M=`pwd` modules
clean:
make -C $(KERN_DIR) M=`pwd` modules clean
rm -rf modules.order
obj-m += button_drv.o
四、測試程序的編寫
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
int main(int argc, char **argv)
{
int fd;
int ret = 0;
unsigned char key_val;
int count = 0;
fd = open("/dev/button", O_RDWR);
if (fd < 0){
printf("can't open!\n");
return -1;
}
while(1){
ret = read(fd, &key_val, 1);
if(ret < 0){
printf(" func read() err\n");
}else{
printf("key_val = 0x%x\n", key_val);
}
}
return ret;
}
五、實際運行
可以看到,驅動以及測試程序可以正常運行,此時CPU使用率不會像查詢方式一樣,高達99%。