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 37 struct 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 47 static struct 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 59 static 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 65 static 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 } 112 113 114 static 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 DEBUG(MTD_DEBUG_LEVEL2, "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 } 141 142 143 static 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 DEBUG(MTD_DEBUG_LEVEL2, "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 } 211 212 213 static 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 DEBUG(MTD_DEBUG_LEVEL2, "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 } 258 259 static 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 } 265 266 static 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 } 281 282 static int mtdblock_open(struct mtd_blktrans_dev *mbd) 283 { 284 struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd); 285 286 DEBUG(MTD_DEBUG_LEVEL1,"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 DEBUG(MTD_DEBUG_LEVEL1, "ok\n"); 307 308 return 0; 309 } 310 311 static int mtdblock_release(struct mtd_blktrans_dev *mbd) 312 { 313 struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd); 314 315 DEBUG(MTD_DEBUG_LEVEL1, "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 /* It was the last usage. Free the cache */ 325 if (mbd->mtd->sync) 326 mbd->mtd->sync(mbd->mtd); 327 vfree(mtdblk->cache_data); 328 } 329 330 mutex_unlock(&mtdblks_lock); 331 332 DEBUG(MTD_DEBUG_LEVEL1, "ok\n"); 333 334 return 0; 335 } 336 337 static int mtdblock_flush(struct mtd_blktrans_dev *dev) 338 { 339 struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd); 340 341 mutex_lock(&mtdblk->cache_mutex); 342 write_cached_data(mtdblk); 343 mutex_unlock(&mtdblk->cache_mutex); 344 345 if (dev->mtd->sync) 346 dev->mtd->sync(dev->mtd); 347 return 0; 348 } 349 350 static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd) 351 { 352 struct mtdblk_dev *dev = kzalloc(sizeof(*dev), GFP_KERNEL); 353 354 if (!dev) 355 return; 356 357 dev->mbd.mtd = mtd; 358 dev->mbd.devnum = mtd->index; 359 360 dev->mbd.size = mtd->size >> 9; 361 dev->mbd.tr = tr; 362 363 if (!(mtd->flags & MTD_WRITEABLE)) 364 dev->mbd.readonly = 1; 365 366 if (add_mtd_blktrans_dev(&dev->mbd)) 367 kfree(dev); 368 } 369 370 static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev) 371 { 372 del_mtd_blktrans_dev(dev); 373 } 374 375 static struct mtd_blktrans_ops mtdblock_tr = { 376 .name = "mtdblock", 377 .major = 31, 378 .part_bits = 0, 379 .blksize = 512, 380 .open = mtdblock_open, 381 .flush = mtdblock_flush, 382 .release = mtdblock_release, 383 .readsect = mtdblock_readsect, 384 .writesect = mtdblock_writesect, 385 .add_mtd = mtdblock_add_mtd, 386 .remove_dev = mtdblock_remove_dev, 387 .owner = THIS_MODULE, 388 }; 389 390 static int __init init_mtdblock(void) 391 { 392 mutex_init(&mtdblks_lock); 393 394 return register_mtd_blktrans(&mtdblock_tr); 395 } 396 397 static void __exit cleanup_mtdblock(void) 398 { 399 deregister_mtd_blktrans(&mtdblock_tr); 400 } 401 402 module_init(init_mtdblock); 403 module_exit(cleanup_mtdblock); 404 405 406 MODULE_LICENSE("GPL"); 407 MODULE_AUTHOR("Nicolas Pitre <nico@fluxnic.net> et al."); 408 MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices"); 409