linuxのブロックデバイスドライバ

  ：

app:      open,read,write "1.txt"
---------------------------------------------       
    : vfat, ext2, ext3, yaffs2, jffs2      (              )
-----------------ll_rw_block-----------------       
                       1.  "  "    
                       2.          (  /   /  )
                        
---------------------------------------------
  :          ,flash


<LINUX         >

  ll_rw_block
        for (i = 0; i < nr; i++) {
            struct buffer_head *bh = bhs[i];
            submit_bh(rw, bh);
                struct bio *bio; //   bh   bio (block input/output)
                submit_bio(rw, bio);
                    //        :   bio     (request)
                    generic_make_request(bio);
                        __generic_make_request(bio);
                            request_queue_t *q = bdev_get_queue(bio->bi_bdev); //       
                            
                            //      "      "
                            ret = q->make_request_fn(q, bio);
                                    //       __make_request
                                    __make_request
                                        //      
                                        elv_merge(q, &req, bio);
                                        
                                        //       ，  bio    
                                        init_request_from_bio(req, bio);
                                        
                                        //        
                                        add_request(q, req);
                                        
                                        //     
                                        __generic_unplug_device(q);
                                                //      "    "
                                                q->request_fn(q);
            
           ？
1.   gendisk: alloc_disk
2.   
2.1   /    : request_queue_t  //        
    blk_init_queue
2.2   gendisk                 //      :     
3.   : add_disk

  ：
drivers\block\xd.c
drivers\block\z2ram.c

  3th,4th:
     :
1. insmod ramblock.ko
2.    : mkdosfs /dev/ramblock
3.   : mount /dev/ramblock /tmp/
4.     : cd /tmp,    vi  
5. cd /; umount /tmp/
6. cat /dev/ramblock > /mnt/ramblock.bin
7.  PC   ramblock.bin
   sudo mount -o loop ramblock.bin /mnt

  5th:
1. insmod ramblock.ko
2. ls /dev/ramblock*
3. fdisk /dev/ramblock

/*   :
 * drivers\block\xd.c
 * drivers\block\z2ram.c
 */

#include <linux/module.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/timer.h>
#include <linux/genhd.h>
#include <linux/hdreg.h>
#include <linux/ioport.h>
#include <linux/init.h>
#include <linux/wait.h>
#include <linux/blkdev.h>
#include <linux/blkpg.h>
#include <linux/delay.h>
#include <linux/io.h>

#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/dma.h>

static struct gendisk *ramblock_disk;
static request_queue_t *ramblock_queue;

static int major;

static DEFINE_SPINLOCK(ramblock_lock);

#define RAMBLOCK_SIZE (1024*1024)
static unsigned char *ramblock_buf;

static int ramblock_getgeo(struct block_device *bdev, struct hd_geometry *geo)
{
	/*   =heads*cylinders*sectors*512 */
	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;
	
	//printk("do_ramblock_request %d
", ++cnt);

	while ((req = elv_next_request(q)) != NULL) {
		/*        :  ,  ,   */
		/*  /  : */
		unsigned long offset = req->sector * 512;

		/*   / : */
		// req->buffer

		/*   : */		
		unsigned long len = req->current_nr_sectors * 512;

		if (rq_data_dir(req) == READ)
		{
			//printk("do_ramblock_request read %d
", ++r_cnt);
			memcpy(req->buffer, ramblock_buf+offset, len);
		}
		else
		{
			//printk("do_ramblock_request write %d
", ++w_cnt);
			memcpy(ramblock_buf+offset, req->buffer, len);
		}		
		
		end_request(req, 1);
	}
}

static int ramblock_init(void)
{
	/* 1.     gendisk    */
	ramblock_disk = alloc_disk(16); /*       :     +1 */

	/* 2.    */
	/* 2.1   /    :        */
	ramblock_queue = blk_init_queue(do_ramblock_request, &ramblock_lock);
	ramblock_disk->queue = ramblock_queue;
	
	/* 2.2       :      */
	major = register_blkdev(0, "ramblock");  /* cat /proc/devices */	
	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);

	/* 3.        */
	ramblock_buf = kzalloc(RAMBLOCK_SIZE, GFP_KERNEL);

	/* 4.    */
	add_disk(ramblock_disk);

	return 0;
}

static void ramblock_exit(void)
{
	unregister_blkdev(major, "ramblock");
	del_gendisk(ramblock_disk);
	put_disk(ramblock_disk);
	blk_cleanup_queue(ramblock_queue);

	kfree(ramblock_buf);
}

module_init(ramblock_init);
module_exit(ramblock_exit);

MODULE_LICENSE("GPL");