块设备驱动程序的框架

/* 参考:
 * 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)
{
    /* 容量=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\n", ++cnt);

    while ((req = elv_next_request(q)) != NULL) {
        /* 数据传输三要素: 源,目的,长度 */
        /* 源/目的: */
        unsigned long offset = req->sector * 512;

        /* 目的/源: */
        // req->buffer

        /* 长度: */        
        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)
{
    /* 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);
    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");
    ramblock_disk->fops        = &ramblock_fops;
    set_capacity(ramblock_disk, RAMBLOCK_SIZE / 512);

    /* 3. 硬件相关操作 */
    ramblock_buf = kzalloc(RAMBLOCK_SIZE, GFP_KERNEL);

    /* 4. 注册 */
    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");