大家好，又见面了，我是你们的朋友全栈君。
platform是一条虚拟的总线。设备用platform_device表示，驱动用platform_driver进行注册，Linux platform driver机制和传统的device driver机制（通过driver_register进行注册）相比，一个明显的优势在于platform机制将设备本身的资源注册进内核，由内核统一管理，在驱动中使用这些资源时通过platform device提供的标准结构进行申请并使用。这样提高了驱动和资源的独立性，并且具有较好的可移植性和安全性（这些标准接口是安全的）。
pltform机制本身使用并不复杂，由两部分组成：platform_device和platform_driver。通过platform机制开发底层驱动的大致流程为：定义platform_deive->注册platform_device->定义platform_driver->注册platform_driver。
platform driver的probe函数是平台总线实现匹配以后首先被调用的函数，因此在其中实现字符设备、块设备、网络设备驱动的初始化是有意义的，这样的设备驱动就是基于平台总线的设备驱动，便于维护。如果添加实际的设备到该平台总线设备驱动模型中，则可以在该函数中实现具体的设备驱动函数的初始化操作，包括设备号的申请，设备的初始化，添加。自动设备文件创建函数的添加等操作。或者是混杂字符设备的相关初始化操作。在remove函数中实现具体的设备的释放，包括设备的删除，设备号的注销等操作。
基于misc device实现一个简单的platform driver（仿照driver/char/sonypi.c）.
fellowplat.h
#ifndef _FELLOW_MISC_H_ #define _FELLOW_MISC_H_ #include <linux/ioctl.h> //#define FELLOW_MISC_MAJOR 199 //#define FELLOW_MISC_NR 2 struct miscdata { int val; char *str; unsigned int size; }; #define FELLOW_MISC_IOC_MAGIC ‘f’ #define FELLOW_MISC_IOC_PRINT _IO(FELLOW_MISC_IOC_MAGIC, 1) #define FELLOW_MISC_IOC_GET _IOR(FELLOW_MISC_IOC_MAGIC, 2, struct miscdata) #define FELLOW_MISC_IOC_SET _IOW(FELLOW_MISC_IOC_MAGIC, 3, struct miscdata) #define FELLOW_MISC_IOC_MAXNR 3 #endif
fellowplat.c
#include <linux/module.h> #include <linux/init.h> //#include <linux/moduleparam.h> #include <linux/types.h> #include <linux/miscdevice.h> #include <linux/platform_device.h> #include <linux/fs.h> #include <linux/errno.h> #include <linux/mm.h> #include <linux/slab.h> #include <asm/io.h> #include <asm/uaccess.h> #include “fellowplat.h” struct fellowmisc_dev{ struct miscdevice misc; struct miscdata data; }; struct fellowmisc_dev *fellowmisc_devp; int fellowmisc_open(struct inode *inode, struct file *filep) { filep->private_data = fellowmisc_devp; return 0; } int fellowmisc_release(struct inode *inode, struct file *filep) { return 0; }
long fellowmisc_ioctl(struct file *filep,unsigned int cmd,unsigned long arg)
{
int ret = 0; struct fellowmisc_dev *devp = (struct fellowmisc_dev *)(filep->private_data); if (_IOC_TYPE(cmd) != FELLOW_MISC_IOC_MAGIC) return -EINVAL; if (_IOC_NR(cmd) > FELLOW_MISC_IOC_MAXNR) return -EINVAL; switch(cmd) { case FELLOW_MISC_IOC_PRINT: printk(“FELLOW_MISC_IOC_PRINTn”); printk(“val:%d, size: %d, str: %sn”, devp->data.val, devp->data.size, devp->data.str); break; case FELLOW_MISC_IOC_SET: printk(“FELLOW_MISC_IOC_SETn”); ret = copy_from_user((unsigned char*)&(devp->data), (unsigned char *)arg, sizeof(struct miscdata)); printk(“set val:%d, size: %d, str: %sn”, devp->data.val, devp->data.size, devp->data.str); break; case FELLOW_MISC_IOC_GET: printk(“FELLOW_MISC_IOC_GETn”); ret = copy_to_user((unsigned char*)arg,(unsigned char*)&(devp->data), sizeof(struct miscdata)); break; default: return -EINVAL;
} return ret; } static const struct file_operations fellowmisc_fops ={ .owner = THIS_MODULE, .open = fellowmisc_open, .release = fellowmisc_release, .unlocked_ioctl = fellowmisc_ioctl, }; static struct miscdevice fellow_misc = { .minor = MISC_DYNAMIC_MINOR, .name = “fellowplat”, .fops = &fellowmisc_fops, }; static struct platform_device *fellow_platform_device; static int fellow_plat_drv_probe(struct platform_device *dev) { int error; printk(“fellow_plat_drv_proben”); fellowmisc_devp = kmalloc(sizeof(struct fellowmisc_dev), GFP_KERNEL); if (!fellowmisc_devp) { error = -ENOMEM; return error; } memset(&(fellowmisc_devp->data), 0, sizeof(fellowmisc_devp->data)); fellowmisc_devp->misc = fellow_misc; error = misc_register(&fellow_misc); return error; } static int fellow_plat_drv_remove(struct platform_device *dev) { int error; if (fellowmisc_devp) kfree(fellowmisc_devp); error = misc_deregister(&fellow_misc); return error; } static struct platform_driver fellow_platform_driver = { .driver = { .name = “fellow”, }, .probe = fellow_plat_drv_probe, .remove = fellow_plat_drv_remove, };
static int fellowplat_init(void) { int error; printk(“fellowplat_initn”); printk(“fellow register drivern”); error = platform_driver_register(&fellow_platform_driver);//注册platform driver if (error) return error;
fellow_platform_device = platform_device_alloc(“fellow”, -1);//名字与platform driver相同。 if (!fellow_platform_device) { error = -ENOMEM; goto err_driver_unregister; }
printk(“fellow register devicen”); error = platform_device_add(fellow_platform_device);//添加platform device if (error) goto err_free_device;
return 0;
err_free_device: platform_device_put(fellow_platform_device); err_driver_unregister: platform_driver_unregister(&fellow_platform_driver); return error; }
static void fellowplat_exit(void) { platform_device_unregister(fellow_platform_device); platform_driver_unregister(&fellow_platform_driver); }
MODULE_AUTHOR(“fellow”); MODULE_LICENSE(“GPL”); module_init(fellowplat_init); module_exit(fellowplat_exit);
app.c
#include <stdio.h> #include <fcntl.h> #include <errno.h> #include <string.h> #include “fellowplat.h” int main(void) { int fd = open(“/dev/fellowplat”, O_RDWR); if (fd < 0) { printf(“open fail:%sn”, strerror(errno)); return -1; } int ret = 0; struct miscdata data; data.val = 18; data.str = “fellow platform device”; data.size = sizeof(“fellow platform device”); if ((ret = ioctl(fd, FELLOW_MISC_IOC_SET, &data)) < 0) { printf(“ioctl set fail:%sn”, strerror(errno)); } struct miscdata getdata; if ((ret = ioctl(fd, FELLOW_MISC_IOC_GET, &getdata)) < 0) { printf(“ioctl get fail:%sn”, strerror(errno)); } printf(“get val:%d, str:%s, size: %dn”, getdata.val, getdata.str, getdata.size); if ((ret = ioctl(fd, FELLOW_MISC_IOC_PRINT, NULL)) < 0) { printf(“ioctl print fail:%sn”, strerror(errno)); } close(fd); return ret; }
运行结果如下
发布者：全栈程序员栈长，转载请注明出处：https://javaforall.cn/154964.html原文链接：https://javaforall.cn
