linux/drivers/mtd/mtdblock.c
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   1/*
   2 * Direct MTD block device access
   3 *
   4 * Copyright © 1999-2010 David Woodhouse <dwmw2@infradead.org>
   5 * Copyright © 2000-2003 Nicolas Pitre <nico@fluxnic.net>
   6 *
   7 * This program is free software; you can redistribute it and/or modify
   8 * it under the terms of the GNU General Public License as published by
   9 * the Free Software Foundation; either version 2 of the License, or
  10 * (at your option) any later version.
  11 *
  12 * This program is distributed in the hope that it will be useful,
  13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 * GNU General Public License for more details.
  16 *
  17 * You should have received a copy of the GNU General Public License
  18 * along with this program; if not, write to the Free Software
  19 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  20 *
  21 */
  22
  23#include <linux/fs.h>
  24#include <linux/init.h>
  25#include <linux/kernel.h>
  26#include <linux/module.h>
  27#include <linux/sched.h>
  28#include <linux/slab.h>
  29#include <linux/types.h>
  30#include <linux/vmalloc.h>
  31
  32#include <linux/mtd/mtd.h>
  33#include <linux/mtd/blktrans.h>
  34#include <linux/mutex.h>
  35
  36
  37struct mtdblk_dev {
  38        struct mtd_blktrans_dev mbd;
  39        int count;
  40        struct mutex cache_mutex;
  41        unsigned char *cache_data;
  42        unsigned long cache_offset;
  43        unsigned int cache_size;
  44        enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state;
  45};
  46
  47static DEFINE_MUTEX(mtdblks_lock);
  48
  49/*
  50 * Cache stuff...
  51 *
  52 * Since typical flash erasable sectors are much larger than what Linux's
  53 * buffer cache can handle, we must implement read-modify-write on flash
  54 * sectors for each block write requests.  To avoid over-erasing flash sectors
  55 * and to speed things up, we locally cache a whole flash sector while it is
  56 * being written to until a different sector is required.
  57 */
  58
  59static void erase_callback(struct erase_info *done)
  60{
  61        wait_queue_head_t *wait_q = (wait_queue_head_t *)done->priv;
  62        wake_up(wait_q);
  63}
  64
  65static int erase_write (struct mtd_info *mtd, unsigned long pos,
  66                        int len, const char *buf)
  67{
  68        struct erase_info erase;
  69        DECLARE_WAITQUEUE(wait, current);
  70        wait_queue_head_t wait_q;
  71        size_t retlen;
  72        int ret;
  73
  74        /*
  75         * First, let's erase the flash block.
  76         */
  77
  78        init_waitqueue_head(&wait_q);
  79        erase.mtd = mtd;
  80        erase.callback = erase_callback;
  81        erase.addr = pos;
  82        erase.len = len;
  83        erase.priv = (u_long)&wait_q;
  84
  85        set_current_state(TASK_INTERRUPTIBLE);
  86        add_wait_queue(&wait_q, &wait);
  87
  88        ret = mtd_erase(mtd, &erase);
  89        if (ret) {
  90                set_current_state(TASK_RUNNING);
  91                remove_wait_queue(&wait_q, &wait);
  92                printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] "
  93                                     "on \"%s\" failed\n",
  94                        pos, len, mtd->name);
  95                return ret;
  96        }
  97
  98        schedule();  /* Wait for erase to finish. */
  99        remove_wait_queue(&wait_q, &wait);
 100
 101        /*
 102         * Next, write the data to flash.
 103         */
 104
 105        ret = mtd_write(mtd, pos, len, &retlen, buf);
 106        if (ret)
 107                return ret;
 108        if (retlen != len)
 109                return -EIO;
 110        return 0;
 111}
 112
 113
 114static int write_cached_data (struct mtdblk_dev *mtdblk)
 115{
 116        struct mtd_info *mtd = mtdblk->mbd.mtd;
 117        int ret;
 118
 119        if (mtdblk->cache_state != STATE_DIRTY)
 120                return 0;
 121
 122        pr_debug("mtdblock: writing cached data for \"%s\" "
 123                        "at 0x%lx, size 0x%x\n", mtd->name,
 124                        mtdblk->cache_offset, mtdblk->cache_size);
 125
 126        ret = erase_write (mtd, mtdblk->cache_offset,
 127                           mtdblk->cache_size, mtdblk->cache_data);
 128        if (ret)
 129                return ret;
 130
 131        /*
 132         * Here we could arguably set the cache state to STATE_CLEAN.
 133         * However this could lead to inconsistency since we will not
 134         * be notified if this content is altered on the flash by other
 135         * means.  Let's declare it empty and leave buffering tasks to
 136         * the buffer cache instead.
 137         */
 138        mtdblk->cache_state = STATE_EMPTY;
 139        return 0;
 140}
 141
 142
 143static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos,
 144                            int len, const char *buf)
 145{
 146        struct mtd_info *mtd = mtdblk->mbd.mtd;
 147        unsigned int sect_size = mtdblk->cache_size;
 148        size_t retlen;
 149        int ret;
 150
 151        pr_debug("mtdblock: write on \"%s\" at 0x%lx, size 0x%x\n",
 152                mtd->name, pos, len);
 153
 154        if (!sect_size)
 155                return mtd_write(mtd, pos, len, &retlen, buf);
 156
 157        while (len > 0) {
 158                unsigned long sect_start = (pos/sect_size)*sect_size;
 159                unsigned int offset = pos - sect_start;
 160                unsigned int size = sect_size - offset;
 161                if( size > len )
 162                        size = len;
 163
 164                if (size == sect_size) {
 165                        /*
 166                         * We are covering a whole sector.  Thus there is no
 167                         * need to bother with the cache while it may still be
 168                         * useful for other partial writes.
 169                         */
 170                        ret = erase_write (mtd, pos, size, buf);
 171                        if (ret)
 172                                return ret;
 173                } else {
 174                        /* Partial sector: need to use the cache */
 175
 176                        if (mtdblk->cache_state == STATE_DIRTY &&
 177                            mtdblk->cache_offset != sect_start) {
 178                                ret = write_cached_data(mtdblk);
 179                                if (ret)
 180                                        return ret;
 181                        }
 182
 183                        if (mtdblk->cache_state == STATE_EMPTY ||
 184                            mtdblk->cache_offset != sect_start) {
 185                                /* fill the cache with the current sector */
 186                                mtdblk->cache_state = STATE_EMPTY;
 187                                ret = mtd_read(mtd, sect_start, sect_size,
 188                                               &retlen, mtdblk->cache_data);
 189                                if (ret)
 190                                        return ret;
 191                                if (retlen != sect_size)
 192                                        return -EIO;
 193
 194                                mtdblk->cache_offset = sect_start;
 195                                mtdblk->cache_size = sect_size;
 196                                mtdblk->cache_state = STATE_CLEAN;
 197                        }
 198
 199                        /* write data to our local cache */
 200                        memcpy (mtdblk->cache_data + offset, buf, size);
 201                        mtdblk->cache_state = STATE_DIRTY;
 202                }
 203
 204                buf += size;
 205                pos += size;
 206                len -= size;
 207        }
 208
 209        return 0;
 210}
 211
 212
 213static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos,
 214                           int len, char *buf)
 215{
 216        struct mtd_info *mtd = mtdblk->mbd.mtd;
 217        unsigned int sect_size = mtdblk->cache_size;
 218        size_t retlen;
 219        int ret;
 220
 221        pr_debug("mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n",
 222                        mtd->name, pos, len);
 223
 224        if (!sect_size)
 225                return mtd_read(mtd, pos, len, &retlen, buf);
 226
 227        while (len > 0) {
 228                unsigned long sect_start = (pos/sect_size)*sect_size;
 229                unsigned int offset = pos - sect_start;
 230                unsigned int size = sect_size - offset;
 231                if (size > len)
 232                        size = len;
 233
 234                /*
 235                 * Check if the requested data is already cached
 236                 * Read the requested amount of data from our internal cache if it
 237                 * contains what we want, otherwise we read the data directly
 238                 * from flash.
 239                 */
 240                if (mtdblk->cache_state != STATE_EMPTY &&
 241                    mtdblk->cache_offset == sect_start) {
 242                        memcpy (buf, mtdblk->cache_data + offset, size);
 243                } else {
 244                        ret = mtd_read(mtd, pos, size, &retlen, buf);
 245                        if (ret)
 246                                return ret;
 247                        if (retlen != size)
 248                                return -EIO;
 249                }
 250
 251                buf += size;
 252                pos += size;
 253                len -= size;
 254        }
 255
 256        return 0;
 257}
 258
 259static int mtdblock_readsect(struct mtd_blktrans_dev *dev,
 260                              unsigned long block, char *buf)
 261{
 262        struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
 263        return do_cached_read(mtdblk, block<<9, 512, buf);
 264}
 265
 266static int mtdblock_writesect(struct mtd_blktrans_dev *dev,
 267                              unsigned long block, char *buf)
 268{
 269        struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
 270        if (unlikely(!mtdblk->cache_data && mtdblk->cache_size)) {
 271                mtdblk->cache_data = vmalloc(mtdblk->mbd.mtd->erasesize);
 272                if (!mtdblk->cache_data)
 273                        return -EINTR;
 274                /* -EINTR is not really correct, but it is the best match
 275                 * documented in man 2 write for all cases.  We could also
 276                 * return -EAGAIN sometimes, but why bother?
 277                 */
 278        }
 279        return do_cached_write(mtdblk, block<<9, 512, buf);
 280}
 281
 282static int mtdblock_open(struct mtd_blktrans_dev *mbd)
 283{
 284        struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd);
 285
 286        pr_debug("mtdblock_open\n");
 287
 288        mutex_lock(&mtdblks_lock);
 289        if (mtdblk->count) {
 290                mtdblk->count++;
 291                mutex_unlock(&mtdblks_lock);
 292                return 0;
 293        }
 294
 295        /* OK, it's not open. Create cache info for it */
 296        mtdblk->count = 1;
 297        mutex_init(&mtdblk->cache_mutex);
 298        mtdblk->cache_state = STATE_EMPTY;
 299        if (!(mbd->mtd->flags & MTD_NO_ERASE) && mbd->mtd->erasesize) {
 300                mtdblk->cache_size = mbd->mtd->erasesize;
 301                mtdblk->cache_data = NULL;
 302        }
 303
 304        mutex_unlock(&mtdblks_lock);
 305
 306        pr_debug("ok\n");
 307
 308        return 0;
 309}
 310
 311static int mtdblock_release(struct mtd_blktrans_dev *mbd)
 312{
 313        struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd);
 314
 315        pr_debug("mtdblock_release\n");
 316
 317        mutex_lock(&mtdblks_lock);
 318
 319        mutex_lock(&mtdblk->cache_mutex);
 320        write_cached_data(mtdblk);
 321        mutex_unlock(&mtdblk->cache_mutex);
 322
 323        if (!--mtdblk->count) {
 324                /*
 325                 * It was the last usage. Free the cache, but only sync if
 326                 * opened for writing.
 327                 */
 328                if (mbd->file_mode & FMODE_WRITE)
 329                        mtd_sync(mbd->mtd);
 330                vfree(mtdblk->cache_data);
 331        }
 332
 333        mutex_unlock(&mtdblks_lock);
 334
 335        pr_debug("ok\n");
 336
 337        return 0;
 338}
 339
 340static int mtdblock_flush(struct mtd_blktrans_dev *dev)
 341{
 342        struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
 343
 344        mutex_lock(&mtdblk->cache_mutex);
 345        write_cached_data(mtdblk);
 346        mutex_unlock(&mtdblk->cache_mutex);
 347        mtd_sync(dev->mtd);
 348        return 0;
 349}
 350
 351static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
 352{
 353        struct mtdblk_dev *dev = kzalloc(sizeof(*dev), GFP_KERNEL);
 354
 355        if (!dev)
 356                return;
 357
 358        dev->mbd.mtd = mtd;
 359        dev->mbd.devnum = mtd->index;
 360
 361        dev->mbd.size = mtd->size >> 9;
 362        dev->mbd.tr = tr;
 363
 364        if (!(mtd->flags & MTD_WRITEABLE))
 365                dev->mbd.readonly = 1;
 366
 367        if (add_mtd_blktrans_dev(&dev->mbd))
 368                kfree(dev);
 369}
 370
 371static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
 372{
 373        del_mtd_blktrans_dev(dev);
 374}
 375
 376static struct mtd_blktrans_ops mtdblock_tr = {
 377        .name           = "mtdblock",
 378        .major          = 31,
 379        .part_bits      = 0,
 380        .blksize        = 512,
 381        .open           = mtdblock_open,
 382        .flush          = mtdblock_flush,
 383        .release        = mtdblock_release,
 384        .readsect       = mtdblock_readsect,
 385        .writesect      = mtdblock_writesect,
 386        .add_mtd        = mtdblock_add_mtd,
 387        .remove_dev     = mtdblock_remove_dev,
 388        .owner          = THIS_MODULE,
 389};
 390
 391static int __init init_mtdblock(void)
 392{
 393        return register_mtd_blktrans(&mtdblock_tr);
 394}
 395
 396static void __exit cleanup_mtdblock(void)
 397{
 398        deregister_mtd_blktrans(&mtdblock_tr);
 399}
 400
 401module_init(init_mtdblock);
 402module_exit(cleanup_mtdblock);
 403
 404
 405MODULE_LICENSE("GPL");
 406MODULE_AUTHOR("Nicolas Pitre <nico@fluxnic.net> et al.");
 407MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices");
 408
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