Linux-2.6.12-rc2

[mirror_ubuntu-zesty-kernel.git] / drivers / s390 / block / dcssblk.c

/*
 * 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/ccwdev.h>         // for s390_root_dev_(un)register()

//#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 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,
};

static ssize_t dcssblk_add_store(struct device * dev, const char * buf,
                                  size_t count);
static ssize_t dcssblk_remove_store(struct device * dev, const char * buf,
                                  size_t count);
static ssize_t dcssblk_save_store(struct device * dev, const char * buf,
                                  size_t count);
static ssize_t dcssblk_save_show(struct device *dev, char *buf);
static ssize_t dcssblk_shared_store(struct device * dev, const char * buf,
                                  size_t count);
static ssize_t dcssblk_shared_show(struct device *dev, 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, 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, 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_put_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, 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, 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, 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 = kmalloc(sizeof(struct dcssblk_dev_info), GFP_KERNEL);
        if (dev_info == NULL) {
                rc = -ENOMEM;
                goto out;
        }
        memset(dev_info, 0, sizeof(struct dcssblk_dev_info));

        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_put_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_put_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, 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_put_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;
        }
        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, bytes_done);
        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, 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,
                                                             "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");