2022年10月13日 | mini2440 入门块设备驱动（用RAM缓存模拟磁盘）代码记录（内核用的是2.6.32.2）

#include

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#define RAMBLOCK_SIZE (1024*1024)

static struct gendisk *grh_gendisk;

static struct request_queue *grh_queue;

static DEFINE_SPINLOCK(grh_spin_lock);

static int major;

static unsigned char *ramblock_buf;

//对队列中的请求进行处理的函数

static void grh_do_ramblock_req(struct request_queue *q){

struct request *req;

static int read_count=0, write_count=0;

unsigned long offset, count;

req = blk_fetch_request(q);

while (req) {

//真正的数据操作

offset = blk_rq_pos(req); //req对应的扇区的偏移量

count = blk_rq_cur_sectors(req); //req对应的数据传输量，以扇区为单位

offset <<= 9;

count <<= 9;

if(rq_data_dir(req) == READ){ //读操作

printk(KERN_EMERG"read count=%dn", ++read_count);

memcpy(req->buffer, ramblock_buf+offset, count); /*从ramdisk把需要搬移的扇区数据移动到req的buffer里面*/

}

else{ //写操作

printk(KERN_EMERG"write count=%dn", ++write_count);

memcpy(ramblock_buf+offset, req->buffer, count);

}

if (!__blk_end_request_cur(req, 0))

req = blk_fetch_request(q);

}

}

//获取柱面和扇区信息的函数，用于向分区工具提供参数

static int grh_getgeo(struct block_device *bdev, struct hd_geometry *geo){

geo->heads = 2; //假设2个面

geo->cylinders = 32; //假设32个柱面

geo->sectors = RAMBLOCK_SIZE/512/2/32; //算出扇区个数

return 0;

}

static struct block_device_operations grh_bdops = {

.owner = THIS_MODULE,

.getgeo = grh_getgeo,

};

static int ram_block_init(void){

//分配gendisk

grh_gendisk = alloc_disk(16); //分区个数为16

//设置gendisk

grh_queue = blk_init_queue(grh_do_ramblock_req, &grh_spin_lock); //创建操作队列

grh_gendisk->queue = grh_queue;

major = register_blkdev(0, "grh_ramblock");

grh_gendisk->major = major;

grh_gendisk->first_minor = 0;

sprintf(grh_gendisk->disk_name, "ramblock");

grh_gendisk->fops = &grh_bdops;

set_capacity(grh_gendisk, RAMBLOCK_SIZE/512); //设置块设备大小为1M

ramblock_buf = kzalloc(RAMBLOCK_SIZE, GFP_KERNEL);

if(NULL == ramblock_buf){

printk(KERN_EMERG"allocate buffer error!n");

}

//注册gendisk

add_disk(grh_gendisk);

return 0;

}

static void ram_block_exit(void){

unregister_blkdev(major, "grh_ramblock");

del_gendisk(grh_gendisk);

put_disk(grh_gendisk);

blk_cleanup_queue(grh_queue);

kfree(ramblock_buf);

return;

}

module_init(ram_block_init);

module_exit(ram_block_exit);

MODULE_AUTHOR("GRH");

MODULE_VERSION("1.0");

MODULE_DESCRIPTION("RAM BLOCK DRIVER");

MODULE_LICENSE("GPL");