Linux 块设备驱动代码编写

#include <linux/module.h> 
#include <linux/kernel.h> 
#include <linux/init.h> 
 
#include <linux/fs.h> 
#include <linux/types.h> 
#include <linux/fcntl.h> 
#include <linux/vmalloc.h> 
#include <linux/blkdev.h> 
#include <linux/hdreg.h> 
 
#define RAMHD_NAME "ramhd" 
#define RAMHD_MAX_DEVICE 2 
#define RAMHD_MAX_PARTITIONS 4 
 
#define RAMHD_SECTOR_SIZE 512 
#define RAMHD_SECTORS 16 
#define RAMHD_HEADS 4 
#define RAMHD_CYLINDERS 256 
 
#define RAMHD_SECTOR_TOTAL (RAMHD_SECTORS * RAMHD_HEADS *RAMHD_CYLINDERS) 
#define RAMHD_SIZE (RAMHD_SECTOR_SIZE * RAMHD_SECTOR_TOTAL) //8mb 
 
typedef struct { 
  unsigned char* data; 
  struct request_queue* queue; 
  struct gendisk* gd; 
}RAMHD_DEV; 
 
static char* sdisk[RAMHD_MAX_DEVICE] = {NULL}; 
static RAMHD_DEV* rdev[RAMHD_MAX_DEVICE] = {NULL}; 
 
static dev_t ramhd_major; 
 
static int ramhd_space_init(void) 
{ 
  int i; 
  int err = 0; 
  for(i = 0; i < RAMHD_MAX_DEVICE; i++){ 
    sdisk[i] = vmalloc(RAMHD_SIZE); 
    if(!sdisk[i]){ 
      err = -ENOMEM; 
      return err; 
    } 
     
    memset(sdisk[i], 0, RAMHD_SIZE); 
  } 
   
  return err; 
} 
 
static void ramhd_space_clean(void) 
{ 
  int i; 
  for(i = 0; i < RAMHD_MAX_DEVICE; i++){ 
    vfree(sdisk[i]); 
  } 
} 
 
static int ramhd_open(struct block_device* bdev, fmode_t mode) 
{ 
  return 0; 
} 
 
static int ramhd_release(struct gendisk*gd, fmode_t mode) 
{ 
  return 0; 
} 
 
static int ramhd_ioctl(struct block_device* bdev, fmode_t mode, unsigned int cmd, unsigned long arg) 
{ 
  int err; 
  struct hd_geometry geo; 
   
  switch(cmd) 
  { 
    case HDIO_GETGEO: 
      err = !access_ok(VERIFY_WRITE, arg, sizeof(geo)); 
      if(err) 
        return -EFAULT; 
         
      geo.cylinders = RAMHD_CYLINDERS; 
      geo.heads = RAMHD_HEADS; 
      geo.sectors = RAMHD_SECTORS; 
      geo.start = get_start_sect(bdev); 
       
      if(copy_to_user((void*)arg, &geo, sizeof(geo))) 
        return -EFAULT; 
       
      return 0; 
  } 
   
  return -ENOTTY; 
} 
 
static struct block_device_operations ramhd_fops = { 
  .owner = THIS_MODULE, 
  .open = ramhd_open, 
  .release = ramhd_release, 
  .ioctl = ramhd_ioctl, 
}; 
 
static int ramhd_make_request(struct request_queue* q, struct bio* bio) 
{ 
  char* pRHdata; 
  char* pBuffer; 
  struct bio_vec* bvec; 
  int i; 
  int err = 0; 
   
  struct block_device* bdev = bio->bi_bdev; 
  RAMHD_DEV* pdev = bdev->bd_disk->private_data; 
   
  if(((bio->bi_sector * RAMHD_SECTOR_SIZE) + bio->bi_size) > RAMHD_SIZE){ 
    err = -EIO; 
    return err; 
  } 
   
  pRHdata = pdev->data + (bio->bi_sector * RAMHD_SECTOR_SIZE); 
  bio_for_each_segment(bvec, bio, i){ 
    pBuffer = kmap(bvec->bv_page) + bvec->bv_offset; 
    switch(bio_data_dir(bio)){ 
      case READ: 
        memcpy(pBuffer, pRHdata, bvec->bv_len); 
        flush_dcache_page(bvec->bv_page); 
        break; 
         
      case WRITE: 
        flush_dcache_page(bvec->bv_page); 
        memcpy(pRHdata, pBuffer, bvec->bv_len); 
        break; 
         
      default: 
        kunmap(bvec->bv_page); 
        goto out; 
    } 
     
    kunmap(bvec->bv_page); 
    pRHdata += bvec->bv_len; 
  } 
   
out: 
  bio_endio(bio, err); 
  return 0; 
} 
 
static int alloc_ramdev(void) 
{ 
  int i; 
  for(i = 0; i < RAMHD_MAX_DEVICE; i++){ 
    rdev[i] = kzalloc(sizeof(RAMHD_DEV), GFP_KERNEL); 
    if(!rdev[i]){ 
      return -ENOMEM; 
    } 
  } 
   
  return 0; 
} 
 
static void clean_ramdev(void) 
{ 
  int i; 
   
  for(i = 0; i < RAMHD_MAX_DEVICE; i++){ 
    if(rdev[i]) 
      kfree(rdev[i]); 
  } 
} 
 
static int __init ramhd_init(void) 
{ 
  int i; 
   
  ramhd_space_init(); 
  alloc_ramdev(); 
   
  ramhd_major = register_blkdev(0, RAMHD_NAME); 
   
  for(i = 0; i < RAMHD_MAX_DEVICE; i++){ 
    rdev[i]->data = sdisk[i]; 
    rdev[i]->queue = blk_alloc_queue(GFP_KERNEL); 
    blk_queue_make_request(rdev[i]->queue, ramhd_make_request); 
     
    rdev[i]->gd = alloc_disk(RAMHD_MAX_PARTITIONS); 
    rdev[i]->gd->major = ramhd_major; 
    rdev[i]->gd->first_minor = i * RAMHD_MAX_PARTITIONS; 
    rdev[i]->gd->fops = &ramhd_fops; 
    rdev[i]->gd->queue = rdev[i]->queue; 
    rdev[i]->gd->private_data = rdev[i]; 
    sprintf(rdev[i]->gd->disk_name, "ramhd%c", 'a' +i); 
    rdev[i]->gd->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO; 
    set_capacity(rdev[i]->gd, RAMHD_SECTOR_TOTAL); 
    add_disk(rdev[i]->gd); 
  } 
   
  return 0; 
} 
 
static void __exit ramhd_exit(void) 
{ 
  int i; 
  for(i = 0; i < RAMHD_MAX_DEVICE; i++){ 
    del_gendisk(rdev[i]->gd); 
    put_disk(rdev[i]->gd); 
    blk_cleanup_queue(rdev[i]->queue); 
  } 
   
  clean_ramdev(); 
  ramhd_space_clean(); 
  unregister_blkdev(ramhd_major, RAMHD_NAME); 
} 
 
module_init(ramhd_init); 
module_exit(ramhd_exit); 
 
MODULE_AUTHOR("dennis__chen@ AMDLinuxFGL"); 
MODULE_DESCRIPTION("The ramdisk implementation with request function"); 
MODULE_LICENSE("GPL"); 

ifneq ($(KERNELRELEASE),) 
obj-m := ramdisk.o 
 
else 
PWD := $(shell pwd) 
KVER := $(shell uname -r) 
KDIR := /lib/modules/$(KVER)/build 
all: 
  $(MAKE) -C $(KDIR) M=$(PWD) modules 
clean: 
  rm -rf .*.cmd *.o *.mod.c *.ko .tmp_versions modules.* Module.* 
endif