1 /* 2 * Direct MTD block device access 3 * 4 * $Id: mtdblock.c,v 1.68 2005/11/07 11:14:20 gleixner Exp $ 5 * 6 * (C) 2000-2003 Nicolas Pitre <nico@cam.org> 7 * (C) 1999-2003 David Woodhouse <dwmw2@infradead.org> 8 */ 9 10 #include <linux/config.h> 11 #include <linux/fs.h> 12 #include <linux/init.h> 13 #include <linux/kernel.h> 14 #include <linux/module.h> 15 #include <linux/sched.h> 16 #include <linux/slab.h> 17 #include <linux/types.h> 18 #include <linux/vmalloc.h> 19 20 #include <linux/mtd/mtd.h> 21 #include <linux/mtd/blktrans.h> 22 #include <linux/mutex.h> 23 24 25 static struct mtdblk_dev { 26 struct mtd_info *mtd; 27 int count; 28 struct mutex cache_mutex; 29 unsigned char *cache_data; 30 unsigned long cache_offset; 31 unsigned int cache_size; 32 enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state; 33 } *mtdblks[MAX_MTD_DEVICES]; 34 35 /* 36 * Cache stuff... 37 * 38 * Since typical flash erasable sectors are much larger than what Linux's 39 * buffer cache can handle, we must implement read-modify-write on flash 40 * sectors for each block write requests. To avoid over-erasing flash sectors 41 * and to speed things up, we locally cache a whole flash sector while it is 42 * being written to until a different sector is required. 43 */ 44 45 static void erase_callback(struct erase_info *done) 46 { 47 wait_queue_head_t *wait_q = (wait_queue_head_t *)done->priv; 48 wake_up(wait_q); 49 } 50 51 static int erase_write (struct mtd_info *mtd, unsigned long pos, 52 int len, const char *buf) 53 { 54 struct erase_info erase; 55 DECLARE_WAITQUEUE(wait, current); 56 wait_queue_head_t wait_q; 57 size_t retlen; 58 int ret; 59 60 /* 61 * First, let's erase the flash block. 62 */ 63 64 init_waitqueue_head(&wait_q); 65 erase.mtd = mtd; 66 erase.callback = erase_callback; 67 erase.addr = pos; 68 erase.len = len; 69 erase.priv = (u_long)&wait_q; 70 71 set_current_state(TASK_INTERRUPTIBLE); 72 add_wait_queue(&wait_q, &wait); 73 74 ret = mtd->erase(mtd, &erase); 75 if (ret) { 76 set_current_state(TASK_RUNNING); 77 remove_wait_queue(&wait_q, &wait); 78 printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] " 79 "on \"%s\" failed\n", 80 pos, len, mtd->name); 81 return ret; 82 } 83 84 schedule(); /* Wait for erase to finish. */ 85 remove_wait_queue(&wait_q, &wait); 86 87 /* 88 * Next, writhe data to flash. 89 */ 90 91 ret = mtd->write(mtd, pos, len, &retlen, buf); 92 if (ret) 93 return ret; 94 if (retlen != len) 95 return -EIO; 96 return 0; 97 } 98 99 100 static int write_cached_data (struct mtdblk_dev *mtdblk) 101 { 102 struct mtd_info *mtd = mtdblk->mtd; 103 int ret; 104 105 if (mtdblk->cache_state != STATE_DIRTY) 106 return 0; 107 108 DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: writing cached data for \"%s\" " 109 "at 0x%lx, size 0x%x\n", mtd->name, 110 mtdblk->cache_offset, mtdblk->cache_size); 111 112 ret = erase_write (mtd, mtdblk->cache_offset, 113 mtdblk->cache_size, mtdblk->cache_data); 114 if (ret) 115 return ret; 116 117 /* 118 * Here we could argubly set the cache state to STATE_CLEAN. 119 * However this could lead to inconsistency since we will not 120 * be notified if this content is altered on the flash by other 121 * means. Let's declare it empty and leave buffering tasks to 122 * the buffer cache instead. 123 */ 124 mtdblk->cache_state = STATE_EMPTY; 125 return 0; 126 } 127 128 129 static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos, 130 int len, const char *buf) 131 { 132 struct mtd_info *mtd = mtdblk->mtd; 133 unsigned int sect_size = mtdblk->cache_size; 134 size_t retlen; 135 int ret; 136 137 DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: write on \"%s\" at 0x%lx, size 0x%x\n", 138 mtd->name, pos, len); 139 140 if (!sect_size) 141 return mtd->write(mtd, pos, len, &retlen, buf); 142 143 while (len > 0) { 144 unsigned long sect_start = (pos/sect_size)*sect_size; 145 unsigned int offset = pos - sect_start; 146 unsigned int size = sect_size - offset; 147 if( size > len ) 148 size = len; 149 150 if (size == sect_size) { 151 /* 152 * We are covering a whole sector. Thus there is no 153 * need to bother with the cache while it may still be 154 * useful for other partial writes. 155 */ 156 ret = erase_write (mtd, pos, size, buf); 157 if (ret) 158 return ret; 159 } else { 160 /* Partial sector: need to use the cache */ 161 162 if (mtdblk->cache_state == STATE_DIRTY && 163 mtdblk->cache_offset != sect_start) { 164 ret = write_cached_data(mtdblk); 165 if (ret) 166 return ret; 167 } 168 169 if (mtdblk->cache_state == STATE_EMPTY || 170 mtdblk->cache_offset != sect_start) { 171 /* fill the cache with the current sector */ 172 mtdblk->cache_state = STATE_EMPTY; 173 ret = mtd->read(mtd, sect_start, sect_size, 174 &retlen, mtdblk->cache_data); 175 if (ret) 176 return ret; 177 if (retlen != sect_size) 178 return -EIO; 179 180 mtdblk->cache_offset = sect_start; 181 mtdblk->cache_size = sect_size; 182 mtdblk->cache_state = STATE_CLEAN; 183 } 184 185 /* write data to our local cache */ 186 memcpy (mtdblk->cache_data + offset, buf, size); 187 mtdblk->cache_state = STATE_DIRTY; 188 } 189 190 buf += size; 191 pos += size; 192 len -= size; 193 } 194 195 return 0; 196 } 197 198 199 static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos, 200 int len, char *buf) 201 { 202 struct mtd_info *mtd = mtdblk->mtd; 203 unsigned int sect_size = mtdblk->cache_size; 204 size_t retlen; 205 int ret; 206 207 DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n", 208 mtd->name, pos, len); 209 210 if (!sect_size) 211 return mtd->read(mtd, pos, len, &retlen, buf); 212 213 while (len > 0) { 214 unsigned long sect_start = (pos/sect_size)*sect_size; 215 unsigned int offset = pos - sect_start; 216 unsigned int size = sect_size - offset; 217 if (size > len) 218 size = len; 219 220 /* 221 * Check if the requested data is already cached 222 * Read the requested amount of data from our internal cache if it 223 * contains what we want, otherwise we read the data directly 224 * from flash. 225 */ 226 if (mtdblk->cache_state != STATE_EMPTY && 227 mtdblk->cache_offset == sect_start) { 228 memcpy (buf, mtdblk->cache_data + offset, size); 229 } else { 230 ret = mtd->read(mtd, pos, size, &retlen, buf); 231 if (ret) 232 return ret; 233 if (retlen != size) 234 return -EIO; 235 } 236 237 buf += size; 238 pos += size; 239 len -= size; 240 } 241 242 return 0; 243 } 244 245 static int mtdblock_readsect(struct mtd_blktrans_dev *dev, 246 unsigned long block, char *buf) 247 { 248 struct mtdblk_dev *mtdblk = mtdblks[dev->devnum]; 249 return do_cached_read(mtdblk, block<<9, 512, buf); 250 } 251 252 static int mtdblock_writesect(struct mtd_blktrans_dev *dev, 253 unsigned long block, char *buf) 254 { 255 struct mtdblk_dev *mtdblk = mtdblks[dev->devnum]; 256 if (unlikely(!mtdblk->cache_data && mtdblk->cache_size)) { 257 mtdblk->cache_data = vmalloc(mtdblk->mtd->erasesize); 258 if (!mtdblk->cache_data) 259 return -EINTR; 260 /* -EINTR is not really correct, but it is the best match 261 * documented in man 2 write for all cases. We could also 262 * return -EAGAIN sometimes, but why bother? 263 */ 264 } 265 return do_cached_write(mtdblk, block<<9, 512, buf); 266 } 267 268 static int mtdblock_open(struct mtd_blktrans_dev *mbd) 269 { 270 struct mtdblk_dev *mtdblk; 271 struct mtd_info *mtd = mbd->mtd; 272 int dev = mbd->devnum; 273 274 DEBUG(MTD_DEBUG_LEVEL1,"mtdblock_open\n"); 275 276 if (mtdblks[dev]) { 277 mtdblks[dev]->count++; 278 return 0; 279 } 280 281 /* OK, it's not open. Create cache info for it */ 282 mtdblk = kmalloc(sizeof(struct mtdblk_dev), GFP_KERNEL); 283 if (!mtdblk) 284 return -ENOMEM; 285 286 memset(mtdblk, 0, sizeof(*mtdblk)); 287 mtdblk->count = 1; 288 mtdblk->mtd = mtd; 289 290 mutex_init(&mtdblk->cache_mutex); 291 mtdblk->cache_state = STATE_EMPTY; 292 if ( !(mtdblk->mtd->flags & MTD_NO_ERASE) && mtdblk->mtd->erasesize) { 293 mtdblk->cache_size = mtdblk->mtd->erasesize; 294 mtdblk->cache_data = NULL; 295 } 296 297 mtdblks[dev] = mtdblk; 298 299 DEBUG(MTD_DEBUG_LEVEL1, "ok\n"); 300 301 return 0; 302 } 303 304 static int mtdblock_release(struct mtd_blktrans_dev *mbd) 305 { 306 int dev = mbd->devnum; 307 struct mtdblk_dev *mtdblk = mtdblks[dev]; 308 309 DEBUG(MTD_DEBUG_LEVEL1, "mtdblock_release\n"); 310 311 mutex_lock(&mtdblk->cache_mutex); 312 write_cached_data(mtdblk); 313 mutex_unlock(&mtdblk->cache_mutex); 314 315 if (!--mtdblk->count) { 316 /* It was the last usage. Free the device */ 317 mtdblks[dev] = NULL; 318 if (mtdblk->mtd->sync) 319 mtdblk->mtd->sync(mtdblk->mtd); 320 vfree(mtdblk->cache_data); 321 kfree(mtdblk); 322 } 323 DEBUG(MTD_DEBUG_LEVEL1, "ok\n"); 324 325 return 0; 326 } 327 328 static int mtdblock_flush(struct mtd_blktrans_dev *dev) 329 { 330 struct mtdblk_dev *mtdblk = mtdblks[dev->devnum]; 331 332 mutex_lock(&mtdblk->cache_mutex); 333 write_cached_data(mtdblk); 334 mutex_unlock(&mtdblk->cache_mutex); 335 336 if (mtdblk->mtd->sync) 337 mtdblk->mtd->sync(mtdblk->mtd); 338 return 0; 339 } 340 341 static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd) 342 { 343 struct mtd_blktrans_dev *dev = kmalloc(sizeof(*dev), GFP_KERNEL); 344 345 if (!dev) 346 return; 347 348 memset(dev, 0, sizeof(*dev)); 349 350 dev->mtd = mtd; 351 dev->devnum = mtd->index; 352 dev->blksize = 512; 353 dev->size = mtd->size >> 9; 354 dev->tr = tr; 355 356 if (!(mtd->flags & MTD_WRITEABLE)) 357 dev->readonly = 1; 358 359 add_mtd_blktrans_dev(dev); 360 } 361 362 static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev) 363 { 364 del_mtd_blktrans_dev(dev); 365 kfree(dev); 366 } 367 368 static struct mtd_blktrans_ops mtdblock_tr = { 369 .name = "mtdblock", 370 .major = 31, 371 .part_bits = 0, 372 .open = mtdblock_open, 373 .flush = mtdblock_flush, 374 .release = mtdblock_release, 375 .readsect = mtdblock_readsect, 376 .writesect = mtdblock_writesect, 377 .add_mtd = mtdblock_add_mtd, 378 .remove_dev = mtdblock_remove_dev, 379 .owner = THIS_MODULE, 380 }; 381 382 static int __init init_mtdblock(void) 383 { 384 return register_mtd_blktrans(&mtdblock_tr); 385 } 386 387 static void __exit cleanup_mtdblock(void) 388 { 389 deregister_mtd_blktrans(&mtdblock_tr); 390 } 391 392 module_init(init_mtdblock); 393 module_exit(cleanup_mtdblock); 394 395 396 MODULE_LICENSE("GPL"); 397 MODULE_AUTHOR("Nicolas Pitre <nico@cam.org> et al."); 398 MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices"); 399