1 /* 2 * Direct MTD block device access 3 * 4 * (C) 2000-2003 Nicolas Pitre <nico@fluxnic.net> 5 * (C) 1999-2003 David Woodhouse <dwmw2@infradead.org> 6 */ 7 8 #include <linux/fs.h> 9 #include <linux/init.h> 10 #include <linux/kernel.h> 11 #include <linux/module.h> 12 #include <linux/sched.h> 13 #include <linux/slab.h> 14 #include <linux/types.h> 15 #include <linux/vmalloc.h> 16 17 #include <linux/mtd/mtd.h> 18 #include <linux/mtd/blktrans.h> 19 #include <linux/mutex.h> 20 21 22 static struct mtdblk_dev { 23 struct mtd_info *mtd; 24 int count; 25 struct mutex cache_mutex; 26 unsigned char *cache_data; 27 unsigned long cache_offset; 28 unsigned int cache_size; 29 enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state; 30 } *mtdblks[MAX_MTD_DEVICES]; 31 32 static struct mutex mtdblks_lock; 33 34 /* 35 * Cache stuff... 36 * 37 * Since typical flash erasable sectors are much larger than what Linux's 38 * buffer cache can handle, we must implement read-modify-write on flash 39 * sectors for each block write requests. To avoid over-erasing flash sectors 40 * and to speed things up, we locally cache a whole flash sector while it is 41 * being written to until a different sector is required. 42 */ 43 44 static void erase_callback(struct erase_info *done) 45 { 46 wait_queue_head_t *wait_q = (wait_queue_head_t *)done->priv; 47 wake_up(wait_q); 48 } 49 50 static int erase_write (struct mtd_info *mtd, unsigned long pos, 51 int len, const char *buf) 52 { 53 struct erase_info erase; 54 DECLARE_WAITQUEUE(wait, current); 55 wait_queue_head_t wait_q; 56 size_t retlen; 57 int ret; 58 59 /* 60 * First, let's erase the flash block. 61 */ 62 63 init_waitqueue_head(&wait_q); 64 erase.mtd = mtd; 65 erase.callback = erase_callback; 66 erase.addr = pos; 67 erase.len = len; 68 erase.priv = (u_long)&wait_q; 69 70 set_current_state(TASK_INTERRUPTIBLE); 71 add_wait_queue(&wait_q, &wait); 72 73 ret = mtd->erase(mtd, &erase); 74 if (ret) { 75 set_current_state(TASK_RUNNING); 76 remove_wait_queue(&wait_q, &wait); 77 printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] " 78 "on \"%s\" failed\n", 79 pos, len, mtd->name); 80 return ret; 81 } 82 83 schedule(); /* Wait for erase to finish. */ 84 remove_wait_queue(&wait_q, &wait); 85 86 /* 87 * Next, writhe data to flash. 88 */ 89 90 ret = mtd->write(mtd, pos, len, &retlen, buf); 91 if (ret) 92 return ret; 93 if (retlen != len) 94 return -EIO; 95 return 0; 96 } 97 98 99 static int write_cached_data (struct mtdblk_dev *mtdblk) 100 { 101 struct mtd_info *mtd = mtdblk->mtd; 102 int ret; 103 104 if (mtdblk->cache_state != STATE_DIRTY) 105 return 0; 106 107 DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: writing cached data for \"%s\" " 108 "at 0x%lx, size 0x%x\n", mtd->name, 109 mtdblk->cache_offset, mtdblk->cache_size); 110 111 ret = erase_write (mtd, mtdblk->cache_offset, 112 mtdblk->cache_size, mtdblk->cache_data); 113 if (ret) 114 return ret; 115 116 /* 117 * Here we could argubly set the cache state to STATE_CLEAN. 118 * However this could lead to inconsistency since we will not 119 * be notified if this content is altered on the flash by other 120 * means. Let's declare it empty and leave buffering tasks to 121 * the buffer cache instead. 122 */ 123 mtdblk->cache_state = STATE_EMPTY; 124 return 0; 125 } 126 127 128 static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos, 129 int len, const char *buf) 130 { 131 struct mtd_info *mtd = mtdblk->mtd; 132 unsigned int sect_size = mtdblk->cache_size; 133 size_t retlen; 134 int ret; 135 136 DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: write on \"%s\" at 0x%lx, size 0x%x\n", 137 mtd->name, pos, len); 138 139 if (!sect_size) 140 return mtd->write(mtd, pos, len, &retlen, buf); 141 142 while (len > 0) { 143 unsigned long sect_start = (pos/sect_size)*sect_size; 144 unsigned int offset = pos - sect_start; 145 unsigned int size = sect_size - offset; 146 if( size > len ) 147 size = len; 148 149 if (size == sect_size) { 150 /* 151 * We are covering a whole sector. Thus there is no 152 * need to bother with the cache while it may still be 153 * useful for other partial writes. 154 */ 155 ret = erase_write (mtd, pos, size, buf); 156 if (ret) 157 return ret; 158 } else { 159 /* Partial sector: need to use the cache */ 160 161 if (mtdblk->cache_state == STATE_DIRTY && 162 mtdblk->cache_offset != sect_start) { 163 ret = write_cached_data(mtdblk); 164 if (ret) 165 return ret; 166 } 167 168 if (mtdblk->cache_state == STATE_EMPTY || 169 mtdblk->cache_offset != sect_start) { 170 /* fill the cache with the current sector */ 171 mtdblk->cache_state = STATE_EMPTY; 172 ret = mtd->read(mtd, sect_start, sect_size, 173 &retlen, mtdblk->cache_data); 174 if (ret) 175 return ret; 176 if (retlen != sect_size) 177 return -EIO; 178 179 mtdblk->cache_offset = sect_start; 180 mtdblk->cache_size = sect_size; 181 mtdblk->cache_state = STATE_CLEAN; 182 } 183 184 /* write data to our local cache */ 185 memcpy (mtdblk->cache_data + offset, buf, size); 186 mtdblk->cache_state = STATE_DIRTY; 187 } 188 189 buf += size; 190 pos += size; 191 len -= size; 192 } 193 194 return 0; 195 } 196 197 198 static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos, 199 int len, char *buf) 200 { 201 struct mtd_info *mtd = mtdblk->mtd; 202 unsigned int sect_size = mtdblk->cache_size; 203 size_t retlen; 204 int ret; 205 206 DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n", 207 mtd->name, pos, len); 208 209 if (!sect_size) 210 return mtd->read(mtd, pos, len, &retlen, buf); 211 212 while (len > 0) { 213 unsigned long sect_start = (pos/sect_size)*sect_size; 214 unsigned int offset = pos - sect_start; 215 unsigned int size = sect_size - offset; 216 if (size > len) 217 size = len; 218 219 /* 220 * Check if the requested data is already cached 221 * Read the requested amount of data from our internal cache if it 222 * contains what we want, otherwise we read the data directly 223 * from flash. 224 */ 225 if (mtdblk->cache_state != STATE_EMPTY && 226 mtdblk->cache_offset == sect_start) { 227 memcpy (buf, mtdblk->cache_data + offset, size); 228 } else { 229 ret = mtd->read(mtd, pos, size, &retlen, buf); 230 if (ret) 231 return ret; 232 if (retlen != size) 233 return -EIO; 234 } 235 236 buf += size; 237 pos += size; 238 len -= size; 239 } 240 241 return 0; 242 } 243 244 static int mtdblock_readsect(struct mtd_blktrans_dev *dev, 245 unsigned long block, char *buf) 246 { 247 struct mtdblk_dev *mtdblk = mtdblks[dev->devnum]; 248 return do_cached_read(mtdblk, block<<9, 512, buf); 249 } 250 251 static int mtdblock_writesect(struct mtd_blktrans_dev *dev, 252 unsigned long block, char *buf) 253 { 254 struct mtdblk_dev *mtdblk = mtdblks[dev->devnum]; 255 if (unlikely(!mtdblk->cache_data && mtdblk->cache_size)) { 256 mtdblk->cache_data = vmalloc(mtdblk->mtd->erasesize); 257 if (!mtdblk->cache_data) 258 return -EINTR; 259 /* -EINTR is not really correct, but it is the best match 260 * documented in man 2 write for all cases. We could also 261 * return -EAGAIN sometimes, but why bother? 262 */ 263 } 264 return do_cached_write(mtdblk, block<<9, 512, buf); 265 } 266 267 static int mtdblock_open(struct mtd_blktrans_dev *mbd) 268 { 269 struct mtdblk_dev *mtdblk; 270 struct mtd_info *mtd = mbd->mtd; 271 int dev = mbd->devnum; 272 273 DEBUG(MTD_DEBUG_LEVEL1,"mtdblock_open\n"); 274 275 mutex_lock(&mtdblks_lock); 276 if (mtdblks[dev]) { 277 mtdblks[dev]->count++; 278 mutex_unlock(&mtdblks_lock); 279 return 0; 280 } 281 282 /* OK, it's not open. Create cache info for it */ 283 mtdblk = kzalloc(sizeof(struct mtdblk_dev), GFP_KERNEL); 284 if (!mtdblk) { 285 mutex_unlock(&mtdblks_lock); 286 return -ENOMEM; 287 } 288 289 mtdblk->count = 1; 290 mtdblk->mtd = mtd; 291 292 mutex_init(&mtdblk->cache_mutex); 293 mtdblk->cache_state = STATE_EMPTY; 294 if ( !(mtdblk->mtd->flags & MTD_NO_ERASE) && mtdblk->mtd->erasesize) { 295 mtdblk->cache_size = mtdblk->mtd->erasesize; 296 mtdblk->cache_data = NULL; 297 } 298 299 mtdblks[dev] = mtdblk; 300 mutex_unlock(&mtdblks_lock); 301 302 DEBUG(MTD_DEBUG_LEVEL1, "ok\n"); 303 304 return 0; 305 } 306 307 static int mtdblock_release(struct mtd_blktrans_dev *mbd) 308 { 309 int dev = mbd->devnum; 310 struct mtdblk_dev *mtdblk = mtdblks[dev]; 311 312 DEBUG(MTD_DEBUG_LEVEL1, "mtdblock_release\n"); 313 314 mutex_lock(&mtdblks_lock); 315 316 mutex_lock(&mtdblk->cache_mutex); 317 write_cached_data(mtdblk); 318 mutex_unlock(&mtdblk->cache_mutex); 319 320 if (!--mtdblk->count) { 321 /* It was the last usage. Free the device */ 322 mtdblks[dev] = NULL; 323 if (mtdblk->mtd->sync) 324 mtdblk->mtd->sync(mtdblk->mtd); 325 vfree(mtdblk->cache_data); 326 kfree(mtdblk); 327 } 328 329 mutex_unlock(&mtdblks_lock); 330 331 DEBUG(MTD_DEBUG_LEVEL1, "ok\n"); 332 333 return 0; 334 } 335 336 static int mtdblock_flush(struct mtd_blktrans_dev *dev) 337 { 338 struct mtdblk_dev *mtdblk = mtdblks[dev->devnum]; 339 340 mutex_lock(&mtdblk->cache_mutex); 341 write_cached_data(mtdblk); 342 mutex_unlock(&mtdblk->cache_mutex); 343 344 if (mtdblk->mtd->sync) 345 mtdblk->mtd->sync(mtdblk->mtd); 346 return 0; 347 } 348 349 static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd) 350 { 351 struct mtd_blktrans_dev *dev = kzalloc(sizeof(*dev), GFP_KERNEL); 352 353 if (!dev) 354 return; 355 356 dev->mtd = mtd; 357 dev->devnum = mtd->index; 358 359 dev->size = mtd->size >> 9; 360 dev->tr = tr; 361 362 if (!(mtd->flags & MTD_WRITEABLE)) 363 dev->readonly = 1; 364 365 add_mtd_blktrans_dev(dev); 366 } 367 368 static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev) 369 { 370 del_mtd_blktrans_dev(dev); 371 kfree(dev); 372 } 373 374 static struct mtd_blktrans_ops mtdblock_tr = { 375 .name = "mtdblock", 376 .major = 31, 377 .part_bits = 0, 378 .blksize = 512, 379 .open = mtdblock_open, 380 .flush = mtdblock_flush, 381 .release = mtdblock_release, 382 .readsect = mtdblock_readsect, 383 .writesect = mtdblock_writesect, 384 .add_mtd = mtdblock_add_mtd, 385 .remove_dev = mtdblock_remove_dev, 386 .owner = THIS_MODULE, 387 }; 388 389 static int __init init_mtdblock(void) 390 { 391 mutex_init(&mtdblks_lock); 392 393 return register_mtd_blktrans(&mtdblock_tr); 394 } 395 396 static void __exit cleanup_mtdblock(void) 397 { 398 deregister_mtd_blktrans(&mtdblock_tr); 399 } 400 401 module_init(init_mtdblock); 402 module_exit(cleanup_mtdblock); 403 404 405 MODULE_LICENSE("GPL"); 406 MODULE_AUTHOR("Nicolas Pitre <nico@fluxnic.net> et al."); 407 MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices"); 408