Linux-FLASH驱动设计二

块设备驱动系统分析：

功能：把内存划出512k，然后利用驱动程序做成块设备进行相应的访问。

#include <linux/module.h>#include <linux/moduleparam.h>#include <linux/init.h>#include <linux/sched.h>#include <linux/kernel.h> /* printk() */#include <linux/slab.h>   /* kmalloc() */#include <linux/fs.h>   /* everything... */#include <linux/errno.h> /* error codes */#include <linux/timer.h>#include <linux/types.h> /* size_t */#include <linux/fcntl.h> /* O_ACCMODE */#include <linux/hdreg.h> /* HDIO_GETGEO */#include <linux/kdev_t.h>#include <linux/vmalloc.h>#include <linux/genhd.h>#include <linux/blkdev.h>#include <linux/buffer_head.h> /* invalidate_bdev */#include <linux/bio.h>MODULE_LICENSE("Dual BSD/GPL");static int major = 0;static int sect_size = 512;static int nsectors = 1024; /** The internal representation of our device.*/struct blk_dev{         int size;                        /* Device size in sectors */         u8 *data;                        /* The data array */         struct request_queue *queue;     /* The device request queue */         struct gendisk *gd;              /* The gendisk structure *///每一个块设备都由一个struct gendisk结构体描述};struct blk_dev *dev;/** Handle an I/O request, in sectors.*/static void blk_transfer(struct blk_dev *dev, unsigned long sector,   unsigned long nsect, char *buffer, int write){unsigned long offset = sector*sect_size;unsigned long nbytes = nsect*sect_size;if ((offset + nbytes) > dev->size) {   printk (KERN_NOTICE "Beyond-end write (%ld %ld)\n", offset, nbytes);   return;}if (write)   memcpy(dev->data + offset, buffer, nbytes);else   memcpy(buffer, dev->data + offset, nbytes);}/** The simple form of the request function.*/static void blk_request(struct request_queue *q){struct request *req;req = blk_fetch_request(q);//取出队列中要处理的请求，接下来应该根据请求里面的信息访问硬件获取数据while (req != NULL) {   struct blk_dev *dev = req->rq_disk->private_data;   blk_transfer(dev, blk_rq_pos(req), blk_rq_cur_sectors(req), req->buffer, rq_data_dir(req));      if(!__blk_end_request_cur(req, 0))//判断请求队列里是否还有剩余请求，如果还有   {req = blk_fetch_request(q);   }}}/** The device operations structure.*/static struct block_device_operations blk_ops = {.owner = THIS_MODULE,};/** Set up our internal device.*/static void setup_device(){/** Get some memory.*/dev->size = nsectors*sect_size;<span style="white-space:pre"></span>//计算分配的设备大小dev->data = vmalloc(dev->size);if (dev->data == NULL) {   printk (KERN_NOTICE "vmalloc failure.\n");   return;}dev->queue = blk_init_queue(blk_request, NULL);//块设备请求队列初始化，第一个参数为请求队列调用函数，第二个参数为信号量if (dev->queue == NULL)goto out_vfree;blk_queue_logical_block_size(dev->queue, sect_size);//指明设备扇区大小dev->queue->queuedata = dev;/** And the gendisk structure.*/dev->gd = alloc_disk(1);//为块设备分配struct gendisk结构if (! dev->gd) {printk (KERN_NOTICE "alloc_disk failure\n");goto out_vfree;}/*初始化struct gendisk结构体

*/ dev->gd->major = major; //块设备主设备号dev->gd->first_minor = 0;//块设备起始次设备号dev->gd->fops = &blk_ops;//块设备操作函数局dev->gd->queue = dev->queue;//块设备请求队列dev->gd->private_data = dev;sprintf (dev->gd->disk_name, "simp_blk%d", 0);//块设备名set_capacity(dev->gd, nsectors*(sect_size/sect_size));//设备块设备扇区数add_disk(dev->gd);//向内核添加（注册）块设备return;out_vfree:if (dev->data) vfree(dev->data);}static int __init blk_init(void){/** Get registered.*/major = register_blkdev(major, "blk");//注册块设备驱动程序，如果主设备号（major）填写为0，内核会自动分配设备号，通过返回值传递给majorif (major <= 0) { printk(KERN_WARNING "blk: unable to get major number\n"); return -EBUSY;}dev = kmalloc(sizeof(struct blk_dev), GFP_KERNEL);if (dev == NULL) goto out_unregister; setup_device();//建立块设备初始化、注册函数，自己实现 return 0;out_unregister:unregister_blkdev(major, "sbd");return -ENOMEM;}static void blk_exit(void){if (dev->gd){del_gendisk(dev->gd);put_disk(dev->gd);}if (dev->queue)blk_cleanup_queue(dev->queue);if (dev->data)vfree(dev->data);unregister_blkdev(major, "blk");kfree(dev);}module_init(blk_init);module_exit(blk_exit);

块设备驱动设计流程图：