linux 下块设备驱动开发学习笔记 2（sbull驱动分析）

最新推荐文章于 2021-05-05 04:02:32 发布

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最新推荐文章于 2021-05-05 04:02:32 发布 · 1.6k 阅读

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本文为BeanHuo原创文章，未经博主允许不得转载。

这篇博客深入探讨了Linux系统下基于gendisk接口的块设备驱动开发，特别关注了如何不使用bio进行驱动实现。内容涉及相关内核头文件及驱动的基本原理。

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//这个驱动是针对gendisk下的buff来实现的，没有用到bio

#include <linux/config.h>

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h> //包含头文件

#include <linux/sched.h>
#include <linux/kernel.h> /* printk() */
#include <linux/slab.h> /* kmalloc() */
#include <linux/fs.h> /* everything... */
#include <linux/errno.h> /* error codes */
#include <linux/timer.h>
#include <linux/types.h> /* size_t */
#include <linux/fcntl.h> /* O_ACCMODE */
#include <linux/hdreg.h> /* HDIO_GETGEO */
#include <linux/kdev_t.h>
#include <linux/vmalloc.h>
#include <linux/genhd.h>
#include <linux/blkdev.h>
#include <linux/buffer_head.h> /* invalidate_bdev */
#include <linux/bio.h>

MODULE_LICENSE("Dual BSD/GPL");
static int sbull_major = 0; //主设备号
module_param(sbull_major, int, 0); //模参数，这个主设备号可以在加载模块时指定一个值
static int hardsect_size = 512;//一个sector大小
module_param(hardsect_size, int, 0);//同上
static int nsectors = 1024; /* How big the drive is */
module_param(nsectors, int, 0);
static int ndevices = 4;
module_param(ndevices, int, 0);
/*
* The different "request modes" we can use.
*/
enum {
RM_SIMPLE = 0, /* The extra-simple request function */
RM_FULL = 1, /* The full-blown version */
RM_NOQUEUE = 2, /* Use make_request */
};
static int request_mode = RM_SIMPLE;
module_param(request_mode, int, 0);
/*
* Minor number and partition management.
*/
#define SBULL_MINORS 16
#define MINOR_SHIFT 4
#define DEVNUM(kdevnum) (MINOR(kdev_t_to_nr(kdevnum)) >> MINOR_SHIFT

#define KERNEL_SECTOR_SIZE 512

#define INVALIDATE_DELAY 30*HZ

/*
* The internal representation of our device.
*/
struct sbull_dev { //用户自定义块设备结构体
int size; /* Device size in sectors */
u8 *data; /* The data array */
short users; /* How many users */
short media_change; /* Flag a media change? */
spinlock_t lock; /* For mutual exclusion */
struct request_queue *queue; /* The device request queue */
struct gendisk *gd; /* The gendisk structure */
struct timer_list timer; /* For simulated media changes */
};

static struct sbull_dev *Devices = NULL;

/*
* Handle an I/O request.
*/
static void sbull_transfer(struct sbull_dev *dev, unsigned long sector,unsigned long nsect, char *buffer, int write)
{
unsigned long offset = sector*KERNEL_SECTOR_SIZE;
unsigned long nbytes = nsect*KERNEL_SECTOR_SIZE;

if ((offset + nbytes) > dev->size) {
printk (KERN_NOTICE "Beyond-end write (%ld %ld)\n", offset, nbytes);
return;
}
if (write)
memcpy(dev->data + offset, buffer, nbytes);
else