struct hd_geometry_geometry dash_typedef struct

用内存代替块设备的总结,相对来简单得多，对内存操作想必大家都很熟悉，直接分配一块内存就可以直接读写操作了

/* 参考:

* drivers\block\xd.c

* drivers\block\z2ram.c

*/

#define RAMBLOCK_SIZE (1024*1024)//一个扇区是512字节

static struct gendisk *ramblock_disk;

static struct request_queue *ramblock_queue;

static DEFINE_SPINLOCK(ramblock_lock);//定义一个自旋锁

static unsigned char *ramblock_buf;

static struct block_device_operations ramblock_fops = {//fops结构体，必须要。struct hd_geometrystruct hd_geometry

.owner= THIS_MODULE,

.getgeo= ramblock_getgeo,//设置heads /cylinders/sectors

};

static int ramblock_getgeo(struct block_device *bdev, struct hd_geometry *geo)

{

/* 容量=heads*cylinders*sectors*512 */

geo->heads = 2;//柱头

geo->cylinders = 32;//柱面

geo->sectors = RAMBLOCK_SIZE/2/32/512;//扇区

return 0;

}

static int ramblock_init(void)

{

/* 1. 分配一个gendisk结构体 */

ramblock_disk = alloc_disk(16); /* 次设备号个数: 分区个数+1 */

/* 2. 设置 */

/* 2.1 分配/设置队列: 提供读写能力 */

ramblock_queue = blk_init_queue(do_ramblock_request, &ramblock_lock);//do_ramblock_request请求队列函数

ramblock_disk->queue = ramblock_queue;

/* 2.2 设置其他属性: 比如容量 */

major = register_blkdev(0, "ramblock"); /* cat /proc/devices */

ramblock_disk->major = major;

ramblock_disk->first_minor = 0;

sprintf(ramblock_disk->disk_name, "ramblock");//把ramblock打印到ramblock_disk->disk_name

ramblock_disk->fops = &ramblock_fops;

set_capacity(ramblock_disk, RAMBLOCK_SIZE / 512);//设置容量

. 硬件相关操作 */

ramblock_buf = kzalloc(RAMBLOCK_SIZE, GFP_KERNEL);//分配一个读写缓冲区

/* 4. 注册 */

add_disk(ramblock_disk);

}

static void do_ramblock_request(struct request_queue * q)//当读写的时候调用这个函数

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