《Linux设备驱动开发详解》源码——vmem_disk.c
/home/lihacker/develop/svn/ldd6410-read-only/training/kernel/drivers/vmem_disk
< vmem_disk.c >
/*
* Sample disk driver, from the beginning.
*/
#include
#include
#include
#include
#include /* printk() */
#include /* kmalloc() */
#include /* everything... */
#include /* error codes */
#include
#include /* size_t */
#include /* O_ACCMODE */
#include /* HDIO_GETGEO */
#include
#include
#include
#include
#include /* invalidate_bdev */
#include
MODULE_LICENSE("Dual BSD/GPL");
static int vmem_disk_major = 0;
module_param(vmem_disk_major, int, 0);
static int hardsect_size = 512;
module_param(hardsect_size, int, 0);
static int nsectors = 1024; /* How big the drive is */
module_param(nsectors, int, 0);
static int ndevices = 4;
module_param(ndevices, int, 0);
/*
* The different "request modes" we can use.
*/
enum {
RM_SIMPLE = 0, /* The extra-simple request function */
RM_FULL = 1, /* The full-blown version */
RM_NOQUEUE = 2, /* Use make_request */
};
static int request_mode = RM_SIMPLE;
module_param(request_mode, int, 0);
/*
* Minor number and partition management.
*/
#define vmem_disk_MINORS 16
#define MINOR_SHIFT 4
#define DEVNUM(kdevnum) (MINOR(kdev_t_to_nr(kdevnum)) >> MINOR_SHIFT
/*
* We can tweak our hardware sector size, but the kernel talks to us
* in terms of small sectors, always.
*/
#define KERNEL_SECTOR_SIZE 512
/*
* After this much idle time, the driver will simulate a media change.
*/
#define INVALIDATE_DELAY 30*HZ
/*
* The internal representation of our device.
*/
struct vmem_disk_dev {
int size; /* Device size in sectors */
u8 *data; /* The data array */
short users; /* How many users */
short media_change; /* Flag a media change? */
spinlock_t lock; /* For mutual exclusion */
struct request_queue *queue; /* The device request queue */
struct gendisk *gd; /* The gendisk structure */
struct timer_list timer; /* For simulated media changes */
};
static struct vmem_disk_dev *Devices = NULL;
/*
* Handle an I/O request.
*/
static void vmem_disk_transfer(struct vmem_disk_dev *dev, unsigned long sector,
unsigned long nsect, char *buffer, int write)
{
unsigned long offset = sector*KERNEL_SECTOR_SIZE;
unsigned long nbytes = nsect*KERNEL_SECTOR_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 vmem_disk_request(struct request_queue *q)
{
struct request *req;
while ((req = elv_next_request(q)) != NULL) {
struct vmem_disk_dev *dev = req->rq_disk->private_data;
if (! blk_fs_request(req)) {
printk (KERN_NOTICE "Skip non-fs request\n");
end_request(req, 0);
continue;
}
vmem_disk_transfer(dev, req->sector, req->current_nr_sectors,
req->buffer, rq_data_dir(req));
end_request(req, 1);
}
}
/*
* Transfer a single BIO.
*/
static int vmem_disk_xfer_bio(struct vmem_disk_dev *dev, struct bio *bio)
{
int i;
struct bio_vec *bvec;
sector_t sector = bio->bi_sector;
/* Do each segment independently. */
bio_for_each_segment(bvec, bio, i) {
char *buffer = __bio_kmap_atomic(bio, i, KM_USER0);
vmem_disk_transfer(dev, sector, bio_cur_sectors(bio),
buffer, bio_data_dir(bio) == WRITE);
sector += bio_cur_sectors(bio);
__bio_kunmap_atomic(bio, KM_USER0);
}
return 0; /* Always "succeed" */
}
/*
* Transfer a full request.
*/
static int vmem_disk_xfer_request(struct vmem_disk_dev *dev, struct request *req)
{
struct req_iterator iter;
int nsect = 0;
struct bio_vec *bvec;
/* Macro rq_for_each_bio is gone.
* In most cases one should use rq_for_each_segment.
*/
rq_for_each_segment(bvec, req, iter) {
char *buffer = __bio_kmap_atomic(iter.bio, iter.i, KM_USER0);
sector_t sector = iter.bio->bi_sector;
vmem_disk_transfer(dev, sector, bio_cur_sectors(iter.bio),
buffer, bio_data_dir(iter.bio) == WRITE);
sector += bio_cur_sectors(iter.bio);
__bio_kunmap_atomic(iter.bio, KM_USER0);
nsect += iter.bio->bi_size/KERNEL_SECTOR_SIZE;
}
return nsect;
}
/*
* Smarter request function that "handles clustering".
*/
static void vmem_disk_full_request(struct request_queue *q)
{
struct request *req;
int sectors_xferred;
struct vmem_disk_dev *dev = q->queuedata;
while ((req = elv_next_request(q)) != NULL) {
if (! blk_fs_request(req)) {
printk (KERN_NOTICE "Skip non-fs request\n");
end_request(req, 0);
continue;
}
sectors_xferred = vmem_disk_xfer_request(dev, req);
end_request (req, 1);
}
}
/*
* The direct make request version.
*/
static int vmem_disk_make_request(struct request_queue *q, struct bio *bio)
{
struct vmem_disk_dev *dev = q->queuedata;
int status;
status = vmem_disk_xfer_bio(dev, bio);
bio_endio(bio, status);
return 0;
}
/*
* Open and close.
*/
static int vmem_disk_open(struct block_device *bdev, fmode_t mode)
{
struct vmem_disk_dev *dev = bdev->bd_disk->private_data;
del_timer_sync(&dev->timer);
spin_lock(&dev->lock);
dev->users++;
spin_unlock(&dev->lock);
return 0;
}
static int vmem_disk_release(struct gendisk *disk, fmode_t mode)
{
struct vmem_disk_dev *dev = disk->private_data;
spin_lock(&dev->lock);
dev->users--;
if (!dev->users) {
dev->timer.expires = jiffies + INVALIDATE_DELAY;
add_timer(&dev->timer);
}
spin_unlock(&dev->lock);
return 0;
}
/*
* Look for a (simulated) media change.
*/
int vmem_disk_media_changed(struct gendisk *gd)
{
struct vmem_disk_dev *dev = gd->private_data;
return dev->media_change;
}
/*
* Revalidate. WE DO NOT TAKE THE LOCK HERE, for fear of deadlocking
* with open. That needs to be reevaluated.
*/
int vmem_disk_revalidate(struct gendisk *gd)
{
struct vmem_disk_dev *dev = gd->private_data;
if (dev->media_change) {
dev->media_change = 0;
memset (dev->data, 0, dev->size);
}
return 0;
}
/*
* The "invalidate" function runs out of the device timer; it sets
* a flag to simulate the removal of the media.
*/
void vmem_disk_invalidate(unsigned long ldev)
{
struct vmem_disk_dev *dev = (struct vmem_disk_dev *) ldev;
spin_lock(&dev->lock);
if (dev->users || !dev->data)
printk (KERN_WARNING "vmem_disk: timer sanity check failed\n");
else
dev->media_change = 1;
spin_unlock(&dev->lock);
}
/*
* The ioctl() implementation
*/
static int vmem_disk_getgeo(struct block_device *bdev, struct hd_geometry *geo)
{
long size;
struct vmem_disk_dev *dev = bdev->bd_disk->private_data;
size = dev->size*(hardsect_size/KERNEL_SECTOR_SIZE);
geo->cylinders = (size & ~0x3f) >> 6;
geo->heads = 4;
geo->sectors = 16;
geo->start = 4;
return 0;
}
/*
* The device operations structure.
*/
static struct block_device_operations vmem_disk_ops = {
.owner = THIS_MODULE,
.open = vmem_disk_open,
.release = vmem_disk_release,
.media_changed = vmem_disk_media_changed,
.revalidate_disk = vmem_disk_revalidate,
.getgeo = vmem_disk_getgeo,
};
/*
* Set up our internal device.
*/
static void setup_device(struct vmem_disk_dev *dev, int which)
{
/*
* Get some memory.
*/
memset (dev, 0, sizeof (struct vmem_disk_dev));
dev->size = nsectors*hardsect_size;
dev->data = vmalloc(dev->size);
if (dev->data == NULL) {
printk (KERN_NOTICE "vmalloc failure.\n");
return;
}
spin_lock_init(&dev->lock);
/*
* The timer which "invalidates" the device.
*/
init_timer(&dev->timer);
dev->timer.data = (unsigned long) dev;
dev->timer.function = vmem_disk_invalidate;
/*
* The I/O queue, depending on whether we are using our own
* make_request function or not.
*/
switch (request_mode) {
case RM_NOQUEUE:
dev->queue = blk_alloc_queue(GFP_KERNEL);
if (dev->queue == NULL)
goto out_vfree;
blk_queue_make_request(dev->queue, vmem_disk_make_request);
break;
case RM_FULL:
dev->queue = blk_init_queue(vmem_disk_full_request, &dev->lock);
if (dev->queue == NULL)
goto out_vfree;
break;
default:
printk(KERN_NOTICE "Bad request mode %d, using simple\n", request_mode);
/* fall into.. */
case RM_SIMPLE:
dev->queue = blk_init_queue(vmem_disk_request, &dev->lock);
if (dev->queue == NULL)
goto out_vfree;
break;
}
blk_queue_hardsect_size(dev->queue, hardsect_size);
dev->queue->queuedata = dev;
/*
* And the gendisk structure.
*/
dev->gd = alloc_disk(vmem_disk_MINORS);
if (! dev->gd) {
printk (KERN_NOTICE "alloc_disk failure\n");
goto out_vfree;
}
dev->gd->major = vmem_disk_major;
dev->gd->first_minor = which*vmem_disk_MINORS;
dev->gd->fops = &vmem_disk_ops;
dev->gd->queue = dev->queue;
dev->gd->private_data = dev;
snprintf (dev->gd->disk_name, 32, "vmem_disk%c", which + 'a');
set_capacity(dev->gd, nsectors*(hardsect_size/KERNEL_SECTOR_SIZE));
add_disk(dev->gd);
return;
out_vfree:
if (dev->data)
vfree(dev->data);
}
static int __init vmem_disk_init(void)
{
int i;
/*
* Get registered.
*/
vmem_disk_major = register_blkdev(vmem_disk_major, "vmem_disk");
if (vmem_disk_major <= 0) {
printk(KERN_WARNING "vmem_disk: unable to get major number\n");
return -EBUSY;
}
/*
* Allocate the device array, and initialize each one.
*/
Devices = kmalloc(ndevices*sizeof (struct vmem_disk_dev), GFP_KERNEL);
if (Devices == NULL)
goto out_unregister;
for (i = 0; i < ndevices; i++)
setup_device(Devices + i, i);
return 0;
out_unregister:
unregister_blkdev(vmem_disk_major, "sbd");
return -ENOMEM;
}
static void vmem_disk_exit(void)
{
int i;
for (i = 0; i < ndevices; i++) {
struct vmem_disk_dev *dev = Devices + i;
del_timer_sync(&dev->timer);
if (dev->gd) {
del_gendisk(dev->gd);
put_disk(dev->gd);
}
if (dev->queue) {
if (request_mode == RM_NOQUEUE)
kobject_put (&dev->queue->kobj);
/* blk_put_queue() is no longer an exported symbol */
else
blk_cleanup_queue(dev->queue);
}
if (dev->data)
vfree(dev->data);
}
unregister_blkdev(vmem_disk_major, "vmem_disk");
kfree(Devices);
}
module_init(vmem_disk_init);
module_exit(vmem_disk_exit);
< Makefile >
KVERS = $(shell uname -r)
# Kernel modules
obj-m += vmem_disk.o
# Specify flags for the module compilation.
#EXTRA_CFLAGS=-g -O0
build: kernel_modules
kernel_modules:
make -C /lib/modules/$(KVERS)/build M=$(CURDIR) modules
clean:
make -C /lib/modules/$(KVERS)/build M=$(CURDIR) clean