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LED Linux驱动程序
测试平台:
驱动程序以及Makefile如下:
#include#include #include #include #include #include static struct class *sun8i_opizero_led_class;//STATUS-LED:PA17#define PIO_BASE 0x1C20800volatile unsigned long *pacfg[4] = {NULL};volatile unsigned long *padat = NULL;static int sun8i_opizero_led_open(struct inode *inode, struct file *file){ //configure pa17 to output mode *pacfg[2] &= ~(3 << 5); return 0;}static ssize_t sun8i_opizero_led_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos){ int val; copy_from_user(&val, buf, count); if (val == 1) *padat |= (1 << 17); else *padat &= ~(1 << 17); return 0;}static struct file_operations sun8i_opizero_led_fops = { .owner = THIS_MODULE, .open = sun8i_opizero_led_open, .write = sun8i_opizero_led_write,};int major;int sun8i_opizero_led_init(void){ major = register_chrdev(0, "led", &sun8i_opizero_led_fops); sun8i_opizero_led_class = class_create(THIS_MODULE, "led"); device_create(sun8i_opizero_led_class, NULL, MKDEV(major, 0), NULL, "led"); pacfg[0] = (volatile unsigned long *)ioremap(PIO_BASE, 0x20); pacfg[1] = pacfg[0] + 1; pacfg[2] = pacfg[1] + 1; pacfg[3] = pacfg[2] + 1; padat = pacfg[3] + 1; return 0;}static void sun8i_opizero_led_exit(void){ unregister_chrdev(major, "led"); device_destroy(sun8i_opizero_led_class, MKDEV(major, 0)); class_destroy(sun8i_opizero_led_class); iounmap(pacfg[0]);}module_init(sun8i_opizero_led_init);module_exit(sun8i_opizero_led_exit);MODULE_DESCRIPTION("LED driver for Xunlong Orange Pi Zero");MODULE_AUTHOR("Techping Chan ");MODULE_LICENSE("GPL");MODULE_ALIAS("platform:orange-pi-zero-led");
obj-m := sun8i_opizero_led.o #编译进模块KERNELDIR := /lib/modules/3.4.113-sun8i/build #此处为linux内核库目录PWD := $(shell pwd) #获取当前目录OUTPUT := $(obj-m) $(obj-m:.o=.ko) $(obj-m:.o=.mod.o) $(obj-m:.o=.mod.c) modules.order Module.symversmodules: $(MAKE) -C $(KERNELDIR) M=$(PWD) modulesclean: rm -rf $(OUTPUT)
在shell中使用以下命令装载驱动程序:
$ make$ insmod sun8i_opizero_led.ko
使用linux c进行测试:
#include#include #include #include int main(int argc, char **argv){ int fd, val = 1; fd = open("/dev/led", O_RDWR); if (fd < 0) printf("can't open led device"); if (argc != 2) { printf("Usage:\n"); printf("%s \n", argv[0]); return 1; } if (strcmp(argv[1], "on") == 0) val = 1; else val = 0; write(fd, &val, 4); return 0;}
进行编译、测试:
$ gcc -o led_test led_test.c$ ./led_test on$ ./led_test off
没问题,成功操作LED!
写Linux驱动程序的步骤无非是:
驱动框架
硬件操作
这里编写的程序和单片机程序的区别就是:
单片机一般不具备MMU(内存管理单元),使用的是物理地址,而现在的SoC一般都带有MMU,使用虚拟地址。这时候我们就需要用Linux C库提供的 ioremap 函数去将物理地址映射为虚拟地址。
通过查看原理图,我们得知LED(STATUS-LED)接在PA17处。
Port Controller Register 的物理基地址为0x01C20800,在 sun8i_opizero_led.c 中使用:
pacfg[0] = (volatile unsigned long *)ioremap(PIO_BASE, 0x20);
把PA_CFG0、PA_CFG1、……PA_PUL1这0x20字节物理地址映射到pacfg[0]~(paccfg[0] + 8)。
之后的操作也是就跟操作单片机一样的位操作了。
static int sun8i_opizero_led_open(struct inode *inode, struct file *file){ //configure pa17 to output *pacfg[2] &= ~(3 << 5); return 0;}
if (val == 1) *padat |= (1 << 17);else *padat &= ~(1 << 17);
对硬件操作封装成固定的驱动程序框架格式,经过编译之后就可以注册到内核以待使用了。