总览
本文使用 linux-2.6.22.6 内核, 使用jz2440开发板.
块设备的驱动框架 驱动框架
ll_rw_block: Low Level Read/Write block devicesubmit_bh: submit Buffer Headsubmit_bio: submit Block IO (Input/Output)elv_merge: elevator merge. 用电梯算法合并数据
硬盘基础概念 块设备为了兼容机械结构的硬盘, 使用了一些硬盘特有的概念.
存储容量 = 磁头数 x 柱面数 x 扇区数 x 512(扇区字节数)存储容量 = 柱面大小 x 柱面数柱面大小 = 磁头数 x 扇区数 x 512(扇区字节数)
英语
中文
说明
Disk
磁盘
就是硬盘
Platter
圆盘
硬盘的盘片
Head
磁头
盘片有2面: 2磁头/圆盘
Track
磁道
圆盘被分割为多个同心圆, 即磁道
Sector
扇区
磁道被分割后的扇形区域
Cylinder
柱面
由多个圆盘的同一磁道构成
Partition
分区
软件概念, 以柱面为单位
参考资料
块设备驱动范例 块设备驱动的实现更为简单. Linux内核做掉了大部分工作, 驱动层只需要专注于硬件的块读写功能.
可以参考内核里的两个文件
drivers\block\xd.c 用于 XT hard disk.drivers\block\z2ram.c ram disk.给出的源码没有做返回值判断, 实际使用时务必参考上面的范例实现错误处理 .
基本步骤如下:
分配gendisk: alloc_disk
设置blk_init_queue
硬件初始化操作
注册: add_disk
ramblock.c #include <linux/major.h> #include <linux/vmalloc.h> #include <linux/init.h> #include <linux/module.h> #include <linux/blkdev.h> #include <linux/hdreg.h> MODULE_LICENSE("GPL" ); MODULE_AUTHOR("DRAAPHO" ); #define DEVICE_NAME "RAMDISK" #define RAMBLOCK_SIZE (1024*1024) static int major;static struct gendisk *ramblock_disk ;static request_queue_t *ramblock_queue;static DEFINE_SPINLOCK (ramblock_lock) static unsigned char *ramblock_buf;static int ramblock_getgeo (struct block_device *bdev, struct hd_geometry *geo) geo->heads = 2 ; geo->cylinders = 32 ; geo->sectors = RAMBLOCK_SIZE/2 /32 /512 ; return 0 ; } static struct block_device_operations ramblock_fops = .owner = THIS_MODULE, .getgeo = ramblock_getgeo, }; static void do_ramblock_request (request_queue_t * q) static int r_cnt = 0 ; static int w_cnt = 0 ; struct request *req ; while ((req = elv_next_request(q)) != NULL ) { unsigned long offset = req->sector*512 ; unsigned long len = req->current_nr_sectors*512 ; if (rq_data_dir(req) == READ) { printk("do_ramblock_request read %d\n" , ++r_cnt); memcpy (req->buffer, ramblock_buf+offset, len); } else { printk("do_ramblock_request write %d\n" , ++w_cnt); memcpy (ramblock_buf+offset, req->buffer, len); } end_request(req, 1 ); } } static int ramblock_init (void ) ramblock_disk = alloc_disk(16 ); ramblock_queue = blk_init_queue(do_ramblock_request, &ramblock_lock); ramblock_disk->queue = ramblock_queue; major = register_blkdev(0 , DEVICE_NAME); ramblock_disk->major = major; ramblock_disk->first_minor = 0 ; sprintf (ramblock_disk->disk_name, "ramblock" ); ramblock_disk->fops = &ramblock_fops; set_capacity(ramblock_disk, RAMBLOCK_SIZE / 512 ); ramblock_buf = kzalloc(RAMBLOCK_SIZE, GFP_KERNEL); add_disk(ramblock_disk); return 0 ; } static void ramblock_exit (void ) del_gendisk(ramblock_disk); put_disk(ramblock_disk); blk_cleanup_queue(ramblock_queue); unregister_blkdev(major, DEVICE_NAME); kfree(ramblock_buf); } module_init(ramblock_init); module_exit(ramblock_exit);
Makefile obj-m := ramblock.o KERN_SRC := /home/draapho/share/jz2440/kernel/linux-2.6.22.6/ PWD := $(shell pwd) modules: make -C $(KERN_SRC) M=$(PWD) modules clean: make -C $(KERN_SRC) M=$(PWD) clean
测试 $ make modules $ insmod ramblock.ko ramblock:do_ramblock_request read 1 unknown partition table $ ls /dev/ramblock* $ cat /proc/devices 254 RAMDISK $ mkdosfs /dev/ramblock $ mount /dev/ramblock /tmp $ vi /tmp/test do_ramblock_request read 43 $ sync do_ramblock_request write 6 do_ramblock_request write 7 ...... $ cp ramblock.c /tmp/ $ sync do_ramblock_request write 11 do_ramblock_request write 12 ...... $ ls /tmp ramblock.c test $ umount /tmp do_ramblock_request write 16 ...... $ ls /tmp $cat /dev/ramblock > ./ramblock.bin do_ramblock_request read ...... $ sudo mount -o loop ramblock.bin /mnt $ ls /mnt ramblock.c test $ sudo umount /mnt $ mkdir /ramdisk $ mount /dev/ramblock /ramdisk $ ls /ramdisk ramblock.c test $ df Filesystem 1k-blocks Used Available Use% Mounted on /dev/ramblock 1004 6 998 1% /ramdisk $ umount /ramdisk $ rmdir /ramdisk $ rmmod ramblock $ insmod ramblock.ko $ ls /dev/ramblock* /dev/ramblock $ fdisk /dev/ramblock m n p Partition number: 1 cylinder value: 1-8 n p Partition number: 2 cylinder value: 9-32 p w $ ls /dev/ramblock* -l brw-rw---- 1 0 0 254, 0 Jan 1 00:01 /dev/ramblock brw-rw---- 1 0 0 254, 1 Jan 1 00:01 /dev/ramblock1 brw-rw---- 1 0 0 254, 2 Jan 1 00:01 /dev/ramblock2 $ mkdosfs /dev/ramblock1 $ mkdosfs /dev/ramblock2 $ mkdir /mnt/ramdisk1 $ mkdir /mnt/ramdisk2 $ mount /dev/ramblock1 /mnt/ramdisk1 $ mount /dev/ramblock2 /mnt/ramdisk2 $ mkdosfs /dev/ramblock $ umount /mnt/ramdisk1 $ umount /mnt/ramdisk2 $ rmdir /mnt/ramdisk1 $ rmdir /mnt/ramdisk2
原创于 DRA&PHO
