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