本文介绍如何使用platform驱动框架来编写一个LED灯驱动，这里采用自定义 platform_device 的方式来编写LED的设备信息。
本实验需要编写一个驱动模块和一个设备模块，其中驱动模块是 platform 驱动程序，设备模块是 platform 的设备信息。当这两个模块都加载成功以后就会匹配成功，然后 platform 驱动模块中的 probe 函数就会执行
1. platform 设备程序编写新建设备文件 leddevice.c 并编写程序
#define CCM_CCGR1_base (0x020C406C)
#define SW_MUX_GPIO1_IO03_base (0x020E0068)
#define SW_PAD_GPIO1_IO03_base (0x020E02F4)
#define GPIO1_DR_base (0x0209C000)
#define GPIO1_GDIR_base (0x0209C004)
#define REGISTER_LENGTH 4
static void led_release(struct device *dev) {
printk("led device released!rn");
}
static struct resource led_resources[] = {
[0] = {
.start = CCM_CCGR1_base,
.end = (CCM_CCGR1_base + REGISTER_LENGTH - 1),
.flags = IORESOURCE_MEM,
},
[1] = {
.start = SW_MUX_GPIO1_IO03_base,
.end = (SW_MUX_GPIO1_IO03_base + REGISTER_LENGTH - 1),
.flags = IORESOURCE_MEM,
},
[2] = {
.start = SW_PAD_GPIO1_IO03_base,
.end = (SW_PAD_GPIO1_IO03_base + REGISTER_LENGTH - 1),
.flags = IORESOURCE_MEM,
},
[3] = {
.start = GPIO1_DR_base,
.end = (GPIO1_DR_base + REGISTER_LENGTH - 1),
.flags = IORESOURCE_MEM,
},
[4] = {
.start = GPIO1_GDIR_base,
.end = (GPIO1_GDIR_base + REGISTER_LENGTH - 1),
.flags = IORESOURCE_MEM,
},
};
static struct platform_device leddevice = {
.name = "imx6ul-led",
.id = -1,
.dev = {
.release = &led_release,
},
.num_resources = ARRAY_SIZE(led_resources),
.resource = led_resources,
};
static int __init leddevice_init(void) {
return platform_device_register(&leddevice);
}
static void __exit leddevice_exit(void) {
platform_device_unregister(&leddevice);
}
module_init(leddevice_init);
module_exit(leddevice_exit);
MODULE_LICENSE("GPL");
2. platform 驱动程序编写
新建驱动文件 leddriver.c 并编写程序
static void __iomem *IMX6U_CCM_CCGR1;
static void __iomem *SW_MUX_GPIO1_IO03;
static void __iomem *SW_PAD_GPIO1_IO03;
static void __iomem *GPIO1_DR;
static void __iomem *GPIO1_GDIR;
struct leddev_dev {
dev_t devid; // 设备号
struct cdev cdev; // cdev
struct class *class; // 类
struct device *device; // 设备
int major; // 主设备号
};
struct leddev_dev leddev; // led 设备
void led0_switch(u8 sta) {
u32 val = 0;
if(sta == LEDON){
val = readl(GPIO1_DR);
val &= ~(1 << 3);
writel(val, GPIO1_DR);
}else if(sta == LEDOFF){
val = readl(GPIO1_DR);
val|= (1 << 3);
writel(val, GPIO1_DR);
}
}
static int led_open(struct inode *inode, struct file *filp) {
filp->private_data = &leddev; // 设置私有数据
return 0;
}
static ssize_t led_write(struct file *filp, const char __user *buf, size_t cnt, loff_t *offt) {
int retvalue;
unsigned char databuf[1];
unsigned char ledstat;
retvalue = copy_from_user(databuf, buf, cnt);
if(retvalue < 0) {
return -EFAULT;
}
ledstat = databuf[0]; //获取状态值
if(ledstat == LEDON) {
led0_switch(LEDON); //打开LED灯
}else if(ledstat == LEDOFF) {
led0_switch(LEDOFF); //关闭LED灯
}
return 0;
}
static struct file_operations led_fops = {
.owner = THIS_MODULE,
.open = led_open,
.write = led_write,
};
static int led_probe(struct platform_device *dev) {
int i = 0;
int ressize[5];
u32 val = 0;
struct resource *ledsource[5];
printk("led driver and device has matched!rn");
for (i = 0; i < 5; i++) {
ledsource[i] = platform_get_resource(dev, IORESOURCE_MEM, i);
if (!ledsource[i]) {
dev_err(&dev->dev, "No MEM resource for always onn");
return -ENXIO;
}
ressize[i] = resource_size(ledsource[i]);
}
IMX6U_CCM_CCGR1 = ioremap(ledsource[0]->start, ressize[0]);
SW_MUX_GPIO1_IO03 = ioremap(ledsource[1]->start, ressize[1]);
SW_PAD_GPIO1_IO03 = ioremap(ledsource[2]->start, ressize[2]);
GPIO1_DR = ioremap(ledsource[3]->start, ressize[3]);
GPIO1_GDIR = ioremap(ledsource[4]->start, ressize[4]);
val = readl(IMX6U_CCM_CCGR1);
val &= ~(3 << 26);
val |= (3 << 26);
writel(val, IMX6U_CCM_CCGR1);
writel(5, SW_MUX_GPIO1_IO03);
writel(0x10B0, SW_PAD_GPIO1_IO03);
val = readl(GPIO1_GDIR);
val &= ~(1 << 3);
val |= (1 << 3);
writel(val, GPIO1_GDIR);
val = readl(GPIO1_DR);
val |= (1 << 3) ;
writel(val, GPIO1_DR);
if (leddev.major) {
leddev.devid = MKDEV(leddev.major, 0);
register_chrdev_region(leddev.devid, LEDDEV_CNT, LEDDEV_NAME);
} else {
alloc_chrdev_region(&leddev.devid, 0, LEDDEV_CNT, LEDDEV_NAME);
leddev.major = MAJOR(leddev.devid);
}
leddev.cdev.owner = THIS_MODULE;
cdev_init(&leddev.cdev, &led_fops);
cdev_add(&leddev.cdev, leddev.devid, LEDDEV_CNT);
leddev.class = class_create(THIS_MODULE, LEDDEV_NAME);
if (IS_ERR(leddev.class)) {
return PTR_ERR(leddev.class);
}
leddev.device = device_create(leddev.class, NULL, leddev.devid, NULL, LEDDEV_NAME);
if (IS_ERR(leddev.device)) {
return PTR_ERR(leddev.device);
}
return 0;
}
static int led_remove(struct platform_device *dev) {
iounmap(IMX6U_CCM_CCGR1);
iounmap(SW_MUX_GPIO1_IO03);
iounmap(SW_PAD_GPIO1_IO03);
iounmap(GPIO1_DR);
iounmap(GPIO1_GDIR);
cdev_del(&leddev.cdev);
unregister_chrdev_region(leddev.devid, LEDDEV_CNT);
device_destroy(leddev.class, leddev.devid);
class_destroy(leddev.class);
return 0;
}
static struct platform_driver led_driver = {
.driver = {
.name = "imx6ul-led",
},
.probe = led_probe,
.remove = led_remove,
};
static int __init leddriver_init(void) {
return platform_driver_register(&led_driver);
}
static void __exit leddriver_exit(void) {
platform_driver_unregister(&led_driver);
}
module_init(leddriver_init);
module_exit(leddriver_exit);
MODULE_LICENSE("GPL");
3. 测试程序编写
新建测试文件 platformledAPP.c，并编写程序
int main(int argc, char *argv[]) {
int fd, retvalue;
char *filename;
unsigned char databuf[2];
if(argc != 3){
printf("Error Usage!rn");
return -1;
}
filename = argv[1];
fd = open(filename, O_RDWR);
if(fd < 0){
printf("file %s open failed!rn", argv[1]);
return -1;
}
databuf[0] = atoi(argv[2]);
retvalue = write(fd, databuf, sizeof(databuf));
if(retvalue < 0){
printf("LED Control Failed!rn");
close(fd);
return -1;
}
retvalue = close(fd);
if(retvalue < 0){
printf("file %s close failed!rn", argv[1]);
return -1;
}
return 0;
}
4. 运行测试
- 修改Makefile编译目标变量
obj-m := leddevice.o leddriver.o
- 使用“make -j32”编译出驱动模块文件
make -j32
- 使用“arm-linux-gnueabihf-gcc”命令编译测试APP
arm-linux-gnueabihf-gcc platformledAPP.c -o platformledAPP
-
将驱动文件和APP可执行文件拷贝至“rootfs/lib/modules/4.1.15”中
-
使用“modprobe”命令加载驱动，加载成功后总线就会进行匹配
depmod #第一次加载驱动时，需使用“depmod”命令 modprobe leddevice.ko modprobe leddriver.ko
根文件系统中/sys/bus/platform/目录下保存着当前板子 platform 总线下的设备和驱动，子目录devices为platform设备，子目录drivers为platform驱动，设备模块和驱动模块加载成功后，会在相应目录下找到对应的设备和驱动
- 使用以下命令打开或者关闭LED灯
./platformledAPP /dev/platled 1 ./platformledAPP /dev/platled 0
