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acrn-kernel/drivers/s390/block/dcssblk.c

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/*
* dcssblk.c -- the S/390 block driver for dcss memory
*
* Authors: Carsten Otte, Stefan Weinhuber, Gerald Schaefer
*/
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/ctype.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <asm/extmem.h>
#include <asm/io.h>
#include <linux/completion.h>
#include <linux/interrupt.h>
#include <asm/s390_rdev.h>
//#define DCSSBLK_DEBUG /* Debug messages on/off */
#define DCSSBLK_NAME "dcssblk"
#define DCSSBLK_MINORS_PER_DISK 1
#define DCSSBLK_PARM_LEN 400
#ifdef DCSSBLK_DEBUG
#define PRINT_DEBUG(x...) printk(KERN_DEBUG DCSSBLK_NAME " debug: " x)
#else
#define PRINT_DEBUG(x...) do {} while (0)
#endif
#define PRINT_INFO(x...) printk(KERN_INFO DCSSBLK_NAME " info: " x)
#define PRINT_WARN(x...) printk(KERN_WARNING DCSSBLK_NAME " warning: " x)
#define PRINT_ERR(x...) printk(KERN_ERR DCSSBLK_NAME " error: " x)
static int dcssblk_open(struct inode *inode, struct file *filp);
static int dcssblk_release(struct inode *inode, struct file *filp);
static int dcssblk_make_request(struct request_queue *q, struct bio *bio);
static int dcssblk_direct_access(struct block_device *bdev, sector_t secnum,
unsigned long *data);
static char dcssblk_segments[DCSSBLK_PARM_LEN] = "\0";
static int dcssblk_major;
static struct block_device_operations dcssblk_devops = {
.owner = THIS_MODULE,
.open = dcssblk_open,
.release = dcssblk_release,
.direct_access = dcssblk_direct_access,
};
static ssize_t dcssblk_add_store(struct device * dev, struct device_attribute *attr, const char * buf,
size_t count);
static ssize_t dcssblk_remove_store(struct device * dev, struct device_attribute *attr, const char * buf,
size_t count);
static ssize_t dcssblk_save_store(struct device * dev, struct device_attribute *attr, const char * buf,
size_t count);
static ssize_t dcssblk_save_show(struct device *dev, struct device_attribute *attr, char *buf);
static ssize_t dcssblk_shared_store(struct device * dev, struct device_attribute *attr, const char * buf,
size_t count);
static ssize_t dcssblk_shared_show(struct device *dev, struct device_attribute *attr, char *buf);
static DEVICE_ATTR(add, S_IWUSR, NULL, dcssblk_add_store);
static DEVICE_ATTR(remove, S_IWUSR, NULL, dcssblk_remove_store);
static DEVICE_ATTR(save, S_IWUSR | S_IRUGO, dcssblk_save_show,
dcssblk_save_store);
static DEVICE_ATTR(shared, S_IWUSR | S_IRUGO, dcssblk_shared_show,
dcssblk_shared_store);
static struct device *dcssblk_root_dev;
struct dcssblk_dev_info {
struct list_head lh;
struct device dev;
char segment_name[BUS_ID_SIZE];
atomic_t use_count;
struct gendisk *gd;
unsigned long start;
unsigned long end;
int segment_type;
unsigned char save_pending;
unsigned char is_shared;
struct request_queue *dcssblk_queue;
};
static struct list_head dcssblk_devices = LIST_HEAD_INIT(dcssblk_devices);
static struct rw_semaphore dcssblk_devices_sem;
/*
* release function for segment device.
*/
static void
dcssblk_release_segment(struct device *dev)
{
PRINT_DEBUG("segment release fn called for %s\n", dev->bus_id);
kfree(container_of(dev, struct dcssblk_dev_info, dev));
module_put(THIS_MODULE);
}
/*
* get a minor number. needs to be called with
* down_write(&dcssblk_devices_sem) and the
* device needs to be enqueued before the semaphore is
* freed.
*/
static inline int
dcssblk_assign_free_minor(struct dcssblk_dev_info *dev_info)
{
int minor, found;
struct dcssblk_dev_info *entry;
if (dev_info == NULL)
return -EINVAL;
for (minor = 0; minor < (1<<MINORBITS); minor++) {
found = 0;
// test if minor available
list_for_each_entry(entry, &dcssblk_devices, lh)
if (minor == entry->gd->first_minor)
found++;
if (!found) break; // got unused minor
}
if (found)
return -EBUSY;
dev_info->gd->first_minor = minor;
return 0;
}
/*
* get the struct dcssblk_dev_info from dcssblk_devices
* for the given name.
* down_read(&dcssblk_devices_sem) must be held.
*/
static struct dcssblk_dev_info *
dcssblk_get_device_by_name(char *name)
{
struct dcssblk_dev_info *entry;
list_for_each_entry(entry, &dcssblk_devices, lh) {
if (!strcmp(name, entry->segment_name)) {
return entry;
}
}
return NULL;
}
/*
* print appropriate error message for segment_load()/segment_type()
* return code
*/
static void
dcssblk_segment_warn(int rc, char* seg_name)
{
switch (rc) {
case -ENOENT:
PRINT_WARN("cannot load/query segment %s, does not exist\n",
seg_name);
break;
case -ENOSYS:
PRINT_WARN("cannot load/query segment %s, not running on VM\n",
seg_name);
break;
case -EIO:
PRINT_WARN("cannot load/query segment %s, hardware error\n",
seg_name);
break;
case -ENOTSUPP:
PRINT_WARN("cannot load/query segment %s, is a multi-part "
"segment\n", seg_name);
break;
case -ENOSPC:
PRINT_WARN("cannot load/query segment %s, overlaps with "
"storage\n", seg_name);
break;
case -EBUSY:
PRINT_WARN("cannot load/query segment %s, overlaps with "
"already loaded dcss\n", seg_name);
break;
case -EPERM:
PRINT_WARN("cannot load/query segment %s, already loaded in "
"incompatible mode\n", seg_name);
break;
case -ENOMEM:
PRINT_WARN("cannot load/query segment %s, out of memory\n",
seg_name);
break;
case -ERANGE:
PRINT_WARN("cannot load/query segment %s, exceeds kernel "
"mapping range\n", seg_name);
break;
default:
PRINT_WARN("cannot load/query segment %s, return value %i\n",
seg_name, rc);
break;
}
}
/*
* device attribute for switching shared/nonshared (exclusive)
* operation (show + store)
*/
static ssize_t
dcssblk_shared_show(struct device *dev, struct device_attribute *attr, char *buf)
{
struct dcssblk_dev_info *dev_info;
dev_info = container_of(dev, struct dcssblk_dev_info, dev);
return sprintf(buf, dev_info->is_shared ? "1\n" : "0\n");
}
static ssize_t
dcssblk_shared_store(struct device *dev, struct device_attribute *attr, const char *inbuf, size_t count)
{
struct dcssblk_dev_info *dev_info;
int rc;
if ((count > 1) && (inbuf[1] != '\n') && (inbuf[1] != '\0')) {
PRINT_WARN("Invalid value, must be 0 or 1\n");
return -EINVAL;
}
down_write(&dcssblk_devices_sem);
dev_info = container_of(dev, struct dcssblk_dev_info, dev);
if (atomic_read(&dev_info->use_count)) {
PRINT_ERR("share: segment %s is busy!\n",
dev_info->segment_name);
rc = -EBUSY;
goto out;
}
if (inbuf[0] == '1') {
// reload segment in shared mode
rc = segment_modify_shared(dev_info->segment_name,
SEGMENT_SHARED);
if (rc < 0) {
BUG_ON(rc == -EINVAL);
if (rc == -EIO || rc == -ENOENT)
goto removeseg;
} else {
dev_info->is_shared = 1;
switch (dev_info->segment_type) {
case SEG_TYPE_SR:
case SEG_TYPE_ER:
case SEG_TYPE_SC:
set_disk_ro(dev_info->gd,1);
}
}
} else if (inbuf[0] == '0') {
// reload segment in exclusive mode
if (dev_info->segment_type == SEG_TYPE_SC) {
PRINT_ERR("Segment type SC (%s) cannot be loaded in "
"non-shared mode\n", dev_info->segment_name);
rc = -EINVAL;
goto out;
}
rc = segment_modify_shared(dev_info->segment_name,
SEGMENT_EXCLUSIVE);
if (rc < 0) {
BUG_ON(rc == -EINVAL);
if (rc == -EIO || rc == -ENOENT)
goto removeseg;
} else {
dev_info->is_shared = 0;
set_disk_ro(dev_info->gd, 0);
}
} else {
PRINT_WARN("Invalid value, must be 0 or 1\n");
rc = -EINVAL;
goto out;
}
rc = count;
goto out;
removeseg:
PRINT_ERR("Could not reload segment %s, removing it now!\n",
dev_info->segment_name);
list_del(&dev_info->lh);
del_gendisk(dev_info->gd);
blk_cleanup_queue(dev_info->dcssblk_queue);
dev_info->gd->queue = NULL;
put_disk(dev_info->gd);
device_unregister(dev);
put_device(dev);
out:
up_write(&dcssblk_devices_sem);
return rc;
}
/*
* device attribute for save operation on current copy
* of the segment. If the segment is busy, saving will
* become pending until it gets released, which can be
* undone by storing a non-true value to this entry.
* (show + store)
*/
static ssize_t
dcssblk_save_show(struct device *dev, struct device_attribute *attr, char *buf)
{
struct dcssblk_dev_info *dev_info;
dev_info = container_of(dev, struct dcssblk_dev_info, dev);
return sprintf(buf, dev_info->save_pending ? "1\n" : "0\n");
}
static ssize_t
dcssblk_save_store(struct device *dev, struct device_attribute *attr, const char *inbuf, size_t count)
{
struct dcssblk_dev_info *dev_info;
if ((count > 1) && (inbuf[1] != '\n') && (inbuf[1] != '\0')) {
PRINT_WARN("Invalid value, must be 0 or 1\n");
return -EINVAL;
}
dev_info = container_of(dev, struct dcssblk_dev_info, dev);
down_write(&dcssblk_devices_sem);
if (inbuf[0] == '1') {
if (atomic_read(&dev_info->use_count) == 0) {
// device is idle => we save immediately
PRINT_INFO("Saving segment %s\n",
dev_info->segment_name);
segment_save(dev_info->segment_name);
} else {
// device is busy => we save it when it becomes
// idle in dcssblk_release
PRINT_INFO("Segment %s is currently busy, it will "
"be saved when it becomes idle...\n",
dev_info->segment_name);
dev_info->save_pending = 1;
}
} else if (inbuf[0] == '0') {
if (dev_info->save_pending) {
// device is busy & the user wants to undo his save
// request
dev_info->save_pending = 0;
PRINT_INFO("Pending save for segment %s deactivated\n",
dev_info->segment_name);
}
} else {
up_write(&dcssblk_devices_sem);
PRINT_WARN("Invalid value, must be 0 or 1\n");
return -EINVAL;
}
up_write(&dcssblk_devices_sem);
return count;
}
/*
* device attribute for adding devices
*/
static ssize_t
dcssblk_add_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
int rc, i;
struct dcssblk_dev_info *dev_info;
char *local_buf;
unsigned long seg_byte_size;
dev_info = NULL;
if (dev != dcssblk_root_dev) {
rc = -EINVAL;
goto out_nobuf;
}
local_buf = kmalloc(count + 1, GFP_KERNEL);
if (local_buf == NULL) {
rc = -ENOMEM;
goto out_nobuf;
}
/*
* parse input
*/
for (i = 0; ((buf[i] != '\0') && (buf[i] != '\n') && i < count); i++) {
local_buf[i] = toupper(buf[i]);
}
local_buf[i] = '\0';
if ((i == 0) || (i > 8)) {
rc = -ENAMETOOLONG;
goto out;
}
/*
* already loaded?
*/
down_read(&dcssblk_devices_sem);
dev_info = dcssblk_get_device_by_name(local_buf);
up_read(&dcssblk_devices_sem);
if (dev_info != NULL) {
PRINT_WARN("Segment %s already loaded!\n", local_buf);
rc = -EEXIST;
goto out;
}
/*
* get a struct dcssblk_dev_info
*/
dev_info = kzalloc(sizeof(struct dcssblk_dev_info), GFP_KERNEL);
if (dev_info == NULL) {
rc = -ENOMEM;
goto out;
}
strcpy(dev_info->segment_name, local_buf);
strlcpy(dev_info->dev.bus_id, local_buf, BUS_ID_SIZE);
dev_info->dev.release = dcssblk_release_segment;
INIT_LIST_HEAD(&dev_info->lh);
dev_info->gd = alloc_disk(DCSSBLK_MINORS_PER_DISK);
if (dev_info->gd == NULL) {
rc = -ENOMEM;
goto free_dev_info;
}
dev_info->gd->major = dcssblk_major;
dev_info->gd->fops = &dcssblk_devops;
dev_info->dcssblk_queue = blk_alloc_queue(GFP_KERNEL);
dev_info->gd->queue = dev_info->dcssblk_queue;
dev_info->gd->private_data = dev_info;
dev_info->gd->driverfs_dev = &dev_info->dev;
/*
* load the segment
*/
rc = segment_load(local_buf, SEGMENT_SHARED,
&dev_info->start, &dev_info->end);
if (rc < 0) {
dcssblk_segment_warn(rc, dev_info->segment_name);
goto dealloc_gendisk;
}
seg_byte_size = (dev_info->end - dev_info->start + 1);
set_capacity(dev_info->gd, seg_byte_size >> 9); // size in sectors
PRINT_INFO("Loaded segment %s, size = %lu Byte, "
"capacity = %lu (512 Byte) sectors\n", local_buf,
seg_byte_size, seg_byte_size >> 9);
dev_info->segment_type = rc;
dev_info->save_pending = 0;
dev_info->is_shared = 1;
dev_info->dev.parent = dcssblk_root_dev;
/*
* get minor, add to list
*/
down_write(&dcssblk_devices_sem);
rc = dcssblk_assign_free_minor(dev_info);
if (rc) {
up_write(&dcssblk_devices_sem);
PRINT_ERR("No free minor number available! "
"Unloading segment...\n");
goto unload_seg;
}
sprintf(dev_info->gd->disk_name, "dcssblk%d",
dev_info->gd->first_minor);
list_add_tail(&dev_info->lh, &dcssblk_devices);
if (!try_module_get(THIS_MODULE)) {
rc = -ENODEV;
goto list_del;
}
/*
* register the device
*/
rc = device_register(&dev_info->dev);
if (rc) {
PRINT_ERR("Segment %s could not be registered RC=%d\n",
local_buf, rc);
module_put(THIS_MODULE);
goto list_del;
}
get_device(&dev_info->dev);
rc = device_create_file(&dev_info->dev, &dev_attr_shared);
if (rc)
goto unregister_dev;
rc = device_create_file(&dev_info->dev, &dev_attr_save);
if (rc)
goto unregister_dev;
add_disk(dev_info->gd);
blk_queue_make_request(dev_info->dcssblk_queue, dcssblk_make_request);
blk_queue_hardsect_size(dev_info->dcssblk_queue, 4096);
switch (dev_info->segment_type) {
case SEG_TYPE_SR:
case SEG_TYPE_ER:
case SEG_TYPE_SC:
set_disk_ro(dev_info->gd,1);
break;
default:
set_disk_ro(dev_info->gd,0);
break;
}
PRINT_DEBUG("Segment %s loaded successfully\n", local_buf);
up_write(&dcssblk_devices_sem);
rc = count;
goto out;
unregister_dev:
PRINT_ERR("device_create_file() failed!\n");
list_del(&dev_info->lh);
blk_cleanup_queue(dev_info->dcssblk_queue);
dev_info->gd->queue = NULL;
put_disk(dev_info->gd);
device_unregister(&dev_info->dev);
segment_unload(dev_info->segment_name);
put_device(&dev_info->dev);
up_write(&dcssblk_devices_sem);
goto out;
list_del:
list_del(&dev_info->lh);
up_write(&dcssblk_devices_sem);
unload_seg:
segment_unload(local_buf);
dealloc_gendisk:
blk_cleanup_queue(dev_info->dcssblk_queue);
dev_info->gd->queue = NULL;
put_disk(dev_info->gd);
free_dev_info:
kfree(dev_info);
out:
kfree(local_buf);
out_nobuf:
return rc;
}
/*
* device attribute for removing devices
*/
static ssize_t
dcssblk_remove_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
struct dcssblk_dev_info *dev_info;
int rc, i;
char *local_buf;
if (dev != dcssblk_root_dev) {
return -EINVAL;
}
local_buf = kmalloc(count + 1, GFP_KERNEL);
if (local_buf == NULL) {
return -ENOMEM;
}
/*
* parse input
*/
for (i = 0; ((*(buf+i)!='\0') && (*(buf+i)!='\n') && i < count); i++) {
local_buf[i] = toupper(buf[i]);
}
local_buf[i] = '\0';
if ((i == 0) || (i > 8)) {
rc = -ENAMETOOLONG;
goto out_buf;
}
down_write(&dcssblk_devices_sem);
dev_info = dcssblk_get_device_by_name(local_buf);
if (dev_info == NULL) {
up_write(&dcssblk_devices_sem);
PRINT_WARN("Segment %s is not loaded!\n", local_buf);
rc = -ENODEV;
goto out_buf;
}
if (atomic_read(&dev_info->use_count) != 0) {
up_write(&dcssblk_devices_sem);
PRINT_WARN("Segment %s is in use!\n", local_buf);
rc = -EBUSY;
goto out_buf;
}
list_del(&dev_info->lh);
del_gendisk(dev_info->gd);
blk_cleanup_queue(dev_info->dcssblk_queue);
dev_info->gd->queue = NULL;
put_disk(dev_info->gd);
device_unregister(&dev_info->dev);
segment_unload(dev_info->segment_name);
PRINT_DEBUG("Segment %s unloaded successfully\n",
dev_info->segment_name);
put_device(&dev_info->dev);
up_write(&dcssblk_devices_sem);
rc = count;
out_buf:
kfree(local_buf);
return rc;
}
static int
dcssblk_open(struct inode *inode, struct file *filp)
{
struct dcssblk_dev_info *dev_info;
int rc;
dev_info = inode->i_bdev->bd_disk->private_data;
if (NULL == dev_info) {
rc = -ENODEV;
goto out;
}
atomic_inc(&dev_info->use_count);
inode->i_bdev->bd_block_size = 4096;
rc = 0;
out:
return rc;
}
static int
dcssblk_release(struct inode *inode, struct file *filp)
{
struct dcssblk_dev_info *dev_info;
int rc;
dev_info = inode->i_bdev->bd_disk->private_data;
if (NULL == dev_info) {
rc = -ENODEV;
goto out;
}
down_write(&dcssblk_devices_sem);
if (atomic_dec_and_test(&dev_info->use_count)
&& (dev_info->save_pending)) {
PRINT_INFO("Segment %s became idle and is being saved now\n",
dev_info->segment_name);
segment_save(dev_info->segment_name);
dev_info->save_pending = 0;
}
up_write(&dcssblk_devices_sem);
rc = 0;
out:
return rc;
}
static int
dcssblk_make_request(request_queue_t *q, struct bio *bio)
{
struct dcssblk_dev_info *dev_info;
struct bio_vec *bvec;
unsigned long index;
unsigned long page_addr;
unsigned long source_addr;
unsigned long bytes_done;
int i;
bytes_done = 0;
dev_info = bio->bi_bdev->bd_disk->private_data;
if (dev_info == NULL)
goto fail;
if ((bio->bi_sector & 7) != 0 || (bio->bi_size & 4095) != 0)
/* Request is not page-aligned. */
goto fail;
if (((bio->bi_size >> 9) + bio->bi_sector)
> get_capacity(bio->bi_bdev->bd_disk)) {
/* Request beyond end of DCSS segment. */
goto fail;
}
/* verify data transfer direction */
if (dev_info->is_shared) {
switch (dev_info->segment_type) {
case SEG_TYPE_SR:
case SEG_TYPE_ER:
case SEG_TYPE_SC:
/* cannot write to these segments */
if (bio_data_dir(bio) == WRITE) {
PRINT_WARN("rejecting write to ro segment %s\n", dev_info->dev.bus_id);
goto fail;
}
}
}
index = (bio->bi_sector >> 3);
bio_for_each_segment(bvec, bio, i) {
page_addr = (unsigned long)
page_address(bvec->bv_page) + bvec->bv_offset;
source_addr = dev_info->start + (index<<12) + bytes_done;
if (unlikely(page_addr & 4095) != 0 || (bvec->bv_len & 4095) != 0)
// More paranoia.
goto fail;
if (bio_data_dir(bio) == READ) {
memcpy((void*)page_addr, (void*)source_addr,
bvec->bv_len);
} else {
memcpy((void*)source_addr, (void*)page_addr,
bvec->bv_len);
}
bytes_done += bvec->bv_len;
}
bio_endio(bio, bytes_done, 0);
return 0;
fail:
bio_io_error(bio, bio->bi_size);
return 0;
}
static int
dcssblk_direct_access (struct block_device *bdev, sector_t secnum,
unsigned long *data)
{
struct dcssblk_dev_info *dev_info;
unsigned long pgoff;
dev_info = bdev->bd_disk->private_data;
if (!dev_info)
return -ENODEV;
if (secnum % (PAGE_SIZE/512))
return -EINVAL;
pgoff = secnum / (PAGE_SIZE / 512);
if ((pgoff+1)*PAGE_SIZE-1 > dev_info->end - dev_info->start)
return -ERANGE;
*data = (unsigned long) (dev_info->start+pgoff*PAGE_SIZE);
return 0;
}
static void
dcssblk_check_params(void)
{
int rc, i, j, k;
char buf[9];
struct dcssblk_dev_info *dev_info;
for (i = 0; (i < DCSSBLK_PARM_LEN) && (dcssblk_segments[i] != '\0');
i++) {
for (j = i; (dcssblk_segments[j] != ',') &&
(dcssblk_segments[j] != '\0') &&
(dcssblk_segments[j] != '(') &&
(j - i) < 8; j++)
{
buf[j-i] = dcssblk_segments[j];
}
buf[j-i] = '\0';
rc = dcssblk_add_store(dcssblk_root_dev, NULL, buf, j-i);
if ((rc >= 0) && (dcssblk_segments[j] == '(')) {
for (k = 0; buf[k] != '\0'; k++)
buf[k] = toupper(buf[k]);
if (!strncmp(&dcssblk_segments[j], "(local)", 7)) {
down_read(&dcssblk_devices_sem);
dev_info = dcssblk_get_device_by_name(buf);
up_read(&dcssblk_devices_sem);
if (dev_info)
dcssblk_shared_store(&dev_info->dev,
NULL, "0\n", 2);
}
}
while ((dcssblk_segments[j] != ',') &&
(dcssblk_segments[j] != '\0'))
{
j++;
}
if (dcssblk_segments[j] == '\0')
break;
i = j;
}
}
/*
* The init/exit functions.
*/
static void __exit
dcssblk_exit(void)
{
int rc;
PRINT_DEBUG("DCSSBLOCK EXIT...\n");
s390_root_dev_unregister(dcssblk_root_dev);
rc = unregister_blkdev(dcssblk_major, DCSSBLK_NAME);
if (rc) {
PRINT_ERR("unregister_blkdev() failed!\n");
}
PRINT_DEBUG("...finished!\n");
}
static int __init
dcssblk_init(void)
{
int rc;
PRINT_DEBUG("DCSSBLOCK INIT...\n");
dcssblk_root_dev = s390_root_dev_register("dcssblk");
if (IS_ERR(dcssblk_root_dev)) {
PRINT_ERR("device_register() failed!\n");
return PTR_ERR(dcssblk_root_dev);
}
rc = device_create_file(dcssblk_root_dev, &dev_attr_add);
if (rc) {
PRINT_ERR("device_create_file(add) failed!\n");
s390_root_dev_unregister(dcssblk_root_dev);
return rc;
}
rc = device_create_file(dcssblk_root_dev, &dev_attr_remove);
if (rc) {
PRINT_ERR("device_create_file(remove) failed!\n");
s390_root_dev_unregister(dcssblk_root_dev);
return rc;
}
rc = register_blkdev(0, DCSSBLK_NAME);
if (rc < 0) {
PRINT_ERR("Can't get dynamic major!\n");
s390_root_dev_unregister(dcssblk_root_dev);
return rc;
}
dcssblk_major = rc;
init_rwsem(&dcssblk_devices_sem);
dcssblk_check_params();
PRINT_DEBUG("...finished!\n");
return 0;
}
module_init(dcssblk_init);
module_exit(dcssblk_exit);
module_param_string(segments, dcssblk_segments, DCSSBLK_PARM_LEN, 0444);
MODULE_PARM_DESC(segments, "Name of DCSS segment(s) to be loaded, "
"comma-separated list, each name max. 8 chars.\n"
"Adding \"(local)\" to segment name equals echoing 0 to "
"/sys/devices/dcssblk/<segment name>/shared after loading "
"the segment - \n"
"e.g. segments=\"mydcss1,mydcss2,mydcss3(local)\"");
MODULE_LICENSE("GPL");
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