在Linux驅動之按鍵驅動編寫(查詢方式)已經寫了一個查詢方式的按鍵驅動，但是查詢方式太占用CPU，接下來利用中斷方式編寫一個驅動程序，使得CPU占有率降低，在按鍵空閑時調用read系統調用的進程可以休眠，還是以以下步驟編寫：
5、編寫Makefile，編譯驅動代碼與測試代碼，在開發板上運行
打開原理圖，確定需要控制的IO端口為GPF0、GPF2、GPG3、GPG11。可以看到它的中斷號為IRQ_EINT0、IRQ_EINT2、IRQ_EINT11、IRQ_EINT19
2、查看芯片手冊，確定IO端口的寄存器地址，可以看到因為用了兩組GPIO端口，所以它的基地址分別為0x56000050、0x56000060。中斷方式的寄存器基地址為0x56000088、0x5600008c、0x56000090
1）、編寫出口、入口函數。代碼如下，具體說明參考Linux驅動之LED驅動編寫
static int second_drv_init(void) { Secondmajor = register_chrdev(0, "buttons", &second_drv_ops);//注冊驅動程序 if(Secondmajor < 0) printk("failes 1 buttons_drv register\n"); second_drv_class = class_create(THIS_MODULE, "buttons");//創建類 if(second_drv_class < 0) printk("failes 2 buttons_drv register\n"); second_drv_class_dev = class_device_create(second_drv_class, NULL, MKDEV(Secondmajor,0), NULL,"buttons");//創建設備節點 if(second_drv_class_dev < 0) printk("failes 3 buttons_drv register\n"); gpfcon = ioremap(0x56000050, 16);//重映射 gpfdat = gpfcon + 1; gpgcon = ioremap(0x56000060, 16);//重映射 gpgdat = gpgcon + 1; printk("register buttons_drv\n"); return 0; } static void second_drv_exit(void) { unregister_chrdev(Secondmajor,"buttons"); class_device_unregister(second_drv_class_dev); class_destroy(second_drv_class); iounmap(gpfcon); iounmap(gpgcon); printk("unregister buttons_drv\n"); } module_init(second_drv_init); module_exit(second_drv_exit);
2）、 添加file_operations 結構體，這個是字符設備驅動的核心結構，所有的應用層調用的函數最終都會調用這個結構下面定義的函數
static struct file_operations third_drv_ops = { .owner = THIS_MODULE, .open = third_drv_open, .read = third_drv_read, .release = third_drv_close,//增加關閉函數 };
3）、分別編寫file_operations 結構體下的open、read、release 函數。其中open函數主要將相應的IO端口配置成中斷功能，並且向內核注冊中斷；read函數主要是在按鍵引腳電平未改變時休眠，然后按鍵引腳電平改變后，將按鍵值傳給應用程序處理。（按鍵值的處理在中斷處理程序中）；relase函數的功能主要是從內核釋放掉open函數注冊的中斷。程序如下：
static int third_drv_open (struct inode * inode, struct file * file) { int ret; ret = request_irq(IRQ_EINT0, buttons_irq, IRQT_BOTHEDGE, "s1", (void * )&pins_desc[0]);//注冊一個外部中斷S1，雙邊沿觸發，dev_id為&pins_desc[0] if(ret) { printk("open failed 1\n"); return -1; } ret = request_irq(IRQ_EINT2, buttons_irq, IRQT_BOTHEDGE, "s2", (void * )& pins_desc[1]);//注冊一個外部中斷S2，雙邊沿觸發，dev_id為&pins_desc[1] if(ret) { printk("open failed 2\n"); return -1; } ret = request_irq(IRQ_EINT11, buttons_irq, IRQT_BOTHEDGE, "s3", (void * )&pins_desc[2]);//注冊一個外部中斷S3，雙邊沿觸發，dev_id為&pins_desc[2] if(ret) { printk("open failed 3\n"); return -1; } ret = request_irq(IRQ_EINT19, buttons_irq, IRQT_BOTHEDGE, "s4", (void * )&pins_desc[3]);//注冊一個外部中斷S4，雙邊沿觸發，dev_id為&pins_desc[3] if(ret) { printk("open failed 4\n"); return -1; } return 0; } static int third_drv_close(struct inode * inode, struct file * file) { free_irq(IRQ_EINT0 ,(void * )&pins_desc[0]);//釋放中斷，根據IRQ_EINT0找到irq_desc結構。根據pins_desc[0]找到irq_desc->action結構 free_irq(IRQ_EINT2 ,(void * )& pins_desc[1]);//釋放中斷，根據IRQ_EINT2找到irq_desc結構。根據pins_desc[2]找到irq_desc->action結構 free_irq(IRQ_EINT11 ,(void * )&pins_desc[2]);//釋放中斷，根據IRQ_EINT11找到irq_desc結構。根據pins_desc[3]找到irq_desc->action結構 free_irq(IRQ_EINT19 ,(void * )&pins_desc[3]);//釋放中斷，根據IRQ_EINT19找到irq_desc結構。根據pins_desc[4]找到irq_desc->action結構 return 0; } static ssize_t third_drv_read(struct file * file, char __user * userbuf, size_t count, loff_t * off) { int ret; if(count != 1) { printk("read error\n"); return -1; } wait_event_interruptible(button_waitq, ev_press);//將當前進程放入等待隊列button_waitq中,並且釋放CPU進入睡眠狀態 ret = copy_to_user(userbuf, &key_val, 1);//將取得的按鍵值傳給上層應用 ev_press = 0;//按鍵已經處理可以繼續睡眠 if(ret) { printk("copy error\n"); return -1; } return 1; }
4）、中斷處理函數的編寫，中斷處理函數利用注冊中斷時傳入的dev_id這個值來判斷是哪個按鍵發生了中斷，dev_iq被賦值為pin_desc結構，如下：
struct pin_desc { unsigned int pin; //是哪個按鍵 unsigned int key_val; //按鍵的按鍵值 }; static struct pin_desc pins_desc[4] = { {S3C2410_GPF0,0x01}, {S3C2410_GPF2,0x02}, {S3C2410_GPG3,0x03}, {S3C2410_GPG11,0x04} };
取得哪個引腳發生的中斷信息后，取得相應的引腳電平，然后確定按鍵值。接着將值傳給key_val，再喚醒調用read的進程，將值直接拷貝給應用程序。具體函數如下
static unsigned int key_val;//全局變量 /* *0x01、0x02、0x03、0x04表示按鍵被按下 */ /* *0x81、0x82、0x83、0x84表示按鍵被松開 */ /* *利用dev_id的值為pins_desc來判斷是哪一個按鍵被按下或松開 */ static irqreturn_t buttons_irq(int irq, void *dev_id) { unsigned int pin_val; struct pin_desc * pin_desc = (struct pin_desc *)dev_id;//取得哪個按鍵被按下的狀態，dev_id是action->dev_id，即在注冊中斷時傳入的&pin_desc[num] pin_val = s3c2410_gpio_getpin(pin_desc->pin); //取得按鍵對應的IO口的電平狀態 if(pin_val) //按鍵松開 key_val = 0x80 | pin_desc->key_val; else key_val = pin_desc->key_val; wake_up_interruptible(&button_waitq); /* 喚醒休眠的進程，即調用read函數的進程 */ ev_press = 1; return IRQ_HANDLED; }
5）、整體代碼
#include <linux/module.h> #include <linux/kernel.h> #include <linux/fs.h> #include <linux/init.h> #include <asm/io.h> //含有iomap函數iounmap函數 #include <asm/uaccess.h>//含有copy_from_user函數 #include <linux/device.h>//含有類相關的處理函數 #include <asm/arch/regs-gpio.h>//含有S3C2410_GPF0等相關的 #include <linux/irq.h> //含有IRQ_HANDLED\IRQ_TYPE_EDGE_RISING #include <asm-arm/irq.h> //含有IRQT_BOTHEDGE觸發類型 #include <linux/interrupt.h> //含有request_irq、free_irq函數 //#include <asm-arm\arch-s3c2410\irqs.h> static struct class *third_drv_class;//類 static struct class_device *third_drv_class_dev;//類下面的設備 static int thirdmajor; static unsigned long *gpfcon = NULL; static unsigned long *gpfdat = NULL; static unsigned long *gpgcon = NULL; static unsigned long *gpgdat = NULL; struct pin_desc { unsigned int pin; //是哪個按鍵 unsigned int key_val; //按鍵的按鍵值 }; static struct pin_desc pins_desc[4] = { {S3C2410_GPF0,0x01}, {S3C2410_GPF2,0x02}, {S3C2410_GPG3,0x03}, {S3C2410_GPG11,0x04} }; unsigned int ev_press; DECLARE_WAIT_QUEUE_HEAD(button_waitq);//注冊一個等待隊列button_waitq static unsigned int key_val;//全局變量 /* *0x01、0x02、0x03、0x04表示按鍵被按下 */ /* *0x81、0x82、0x83、0x84表示按鍵被松開 */ /* *利用dev_id的值為pins_desc來判斷是哪一個按鍵被按下或松開 */ static irqreturn_t buttons_irq(int irq, void *dev_id) { unsigned int pin_val; struct pin_desc * pin_desc = (struct pin_desc *)dev_id;//取得哪個按鍵被按下的狀態，dev_id是action->dev_id，即在注冊中斷時傳入的&pin_desc[num] pin_val = s3c2410_gpio_getpin(pin_desc->pin); //取得按鍵對應的IO口的電平狀態 if(pin_val) //按鍵松開 key_val = 0x80 | pin_desc->key_val; else key_val = pin_desc->key_val; wake_up_interruptible(&button_waitq); /* 喚醒休眠的進程，即調用read函數的進程 */ ev_press = 1; return IRQ_HANDLED; } static int third_drv_open (struct inode * inode, struct file * file) { int ret; ret = request_irq(IRQ_EINT0, buttons_irq, IRQT_BOTHEDGE, "s1", (void * )&pins_desc[0]);//注冊一個外部中斷S1，雙邊沿觸發，dev_id為&pins_desc[0] if(ret) { printk("open failed 1\n"); return -1; } ret = request_irq(IRQ_EINT2, buttons_irq, IRQT_BOTHEDGE, "s2", (void * )& pins_desc[1]);//注冊一個外部中斷S2，雙邊沿觸發，dev_id為&pins_desc[1] if(ret) { printk("open failed 2\n"); return -1; } ret = request_irq(IRQ_EINT11, buttons_irq, IRQT_BOTHEDGE, "s3", (void * )&pins_desc[2]);//注冊一個外部中斷S3，雙邊沿觸發，dev_id為&pins_desc[2] if(ret) { printk("open failed 3\n"); return -1; } ret = request_irq(IRQ_EINT19, buttons_irq, IRQT_BOTHEDGE, "s4", (void * )&pins_desc[3]);//注冊一個外部中斷S4，雙邊沿觸發，dev_id為&pins_desc[3] if(ret) { printk("open failed 4\n"); return -1; } return 0; } static int third_drv_close(struct inode * inode, struct file * file) { free_irq(IRQ_EINT0 ,(void * )&pins_desc[0]);//釋放中斷，根據IRQ_EINT0找到irq_desc結構。根據pins_desc[0]找到irq_desc->action結構 free_irq(IRQ_EINT2 ,(void * )& pins_desc[1]);//釋放中斷，根據IRQ_EINT2找到irq_desc結構。根據pins_desc[2]找到irq_desc->action結構 free_irq(IRQ_EINT11 ,(void * )&pins_desc[2]);//釋放中斷，根據IRQ_EINT11找到irq_desc結構。根據pins_desc[3]找到irq_desc->action結構 free_irq(IRQ_EINT19 ,(void * )&pins_desc[3]);//釋放中斷，根據IRQ_EINT19找到irq_desc結構。根據pins_desc[4]找到irq_desc->action結構 return 0; } static ssize_t third_drv_read(struct file * file, char __user * userbuf, size_t count, loff_t * off) { int ret; if(count != 1) { printk("read error\n"); return -1; } wait_event_interruptible(button_waitq, ev_press);//將當前進程放入等待隊列button_waitq中,並且釋放CPU進入睡眠狀態 ret = copy_to_user(userbuf, &key_val, 1);//將取得的按鍵值傳給上層應用 ev_press = 0;//按鍵已經處理可以繼續睡眠 if(ret) { printk("copy error\n"); return -1; } return 1; } static struct file_operations third_drv_ops = { .owner = THIS_MODULE, .open = third_drv_open, .read = third_drv_read, .release = third_drv_close,//增加關閉函數 }; static int third_drv_init(void) { thirdmajor = register_chrdev(0, "buttons", &third_drv_ops);//注冊驅動程序 if(thirdmajor < 0) printk("failes 1 buttons_drv register\n"); third_drv_class = class_create(THIS_MODULE, "buttons");//創建類 if(third_drv_class < 0) printk("failes 2 buttons_drv register\n"); third_drv_class_dev = class_device_create(third_drv_class, NULL, MKDEV(thirdmajor,0), NULL,"buttons");//創建設備節點 if(third_drv_class_dev < 0) printk("failes 3 buttons_drv register\n"); gpfcon = ioremap(0x56000050, 16);//重映射 gpfdat = gpfcon + 1; gpgcon = ioremap(0x56000060, 16);//重映射 gpgdat = gpgcon + 1; printk("register buttons_drv\n"); return 0; } static void third_drv_exit(void) { unregister_chrdev(thirdmajor,"buttons"); class_device_unregister(third_drv_class_dev); class_destroy(third_drv_class); iounmap(gpfcon); iounmap(gpgcon); printk("unregister buttons_drv\n"); } module_init(third_drv_init); module_exit(third_drv_exit); MODULE_LICENSE("GPL");
測試程序實現四個按鍵中有一個按鍵按下時，打印出這個按鍵的按鍵值。./third_test。直接看代碼
#include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <stdio.h> /* *usage ./buttonstest */ int main(int argc, char **argv) { int fd; char* filename="dev/buttons"; unsigned char key_val; unsigned long cnt=0; fd = open(filename, O_RDWR);//打開dev/firstdrv設備文件 if (fd < 0)//小於0說明沒有成功 { printf("error, can't open %s\n", filename); return 0; } if(argc !=1) { printf("Usage : %s ",argv[0]); return 0; } while(1) { read(fd, &key_val, 1); printf("key_val: %x\n",key_val); } return 0; }
5、編寫Makefile，編譯驅動代碼與測試代碼，在開發板上運行
Makefile源碼如下：
KERN_DIR = /work/system/linux-2.6.22.6 all: make -C $(KERN_DIR) M=`pwd` modules //M='pwd'表示當前目錄。這句話的意思是利用內核目錄下的Makefile規則來編譯當前目錄下的模塊 clean: make -C $(KERN_DIR) M=`pwd` modules clean rm -rf modules.order obj-m +=third_drv.o//調用內核目錄下Makefile編譯時需要用到這個參數
1）、然后在當前目錄下make后編譯出third_drv.ko文件
2）、arm-linux-gcc -o third_test third_test.c編譯出third_test測試程序
3）、cp third_drv.ko third_test /work/nfs_root將編譯出來的文件拷貝到開發板掛接的網絡文件系統上
4）、執行insmod third_drv.ko加載驅動。
5）、./third_test測試程序,按下按鍵，成功打印按鍵值，用top命令查看應用程序發現third_test程序占用了0%的CPU資源，驅動程序相比查詢方式的驅動改善了。