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, &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 if (mtdblks[dev]) { 276 mtdblks[dev]->count++; 277 return 0; 278 } 279 280 /* OK, it's not open. Create cache info for it */ 281 mtdblk = kmalloc(sizeof(struct mtdblk_dev), GFP_KERNEL); 282 if (!mtdblk) 283 return -ENOMEM; 284 285 memset(mtdblk, 0, sizeof(*mtdblk)); 286 mtdblk->count = 1; 287 mtdblk->mtd = mtd; 288 289 mutex_init(&mtdblk->cache_mutex); 290 mtdblk->cache_state = STATE_EMPTY; 291 if ((mtdblk->mtd->flags & MTD_CAP_RAM) != MTD_CAP_RAM && 292 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