1 /* 2 * Direct MTD block device access 3 * 4 * $Id: mtdblock.c,v 1.66 2004/11/25 13:52:52 joern 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/types.h> 12 #include <linux/module.h> 13 #include <linux/kernel.h> 14 #include <linux/fs.h> 15 #include <linux/init.h> 16 #include <linux/slab.h> 17 #include <linux/vmalloc.h> 18 #include <linux/sched.h> /* TASK_* */ 19 #include <linux/mtd/mtd.h> 20 #include <linux/mtd/blktrans.h> 21 22 static struct mtdblk_dev { 23 struct mtd_info *mtd; 24 int count; 25 struct semaphore cache_sem; 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, &retlen, mtdblk->cache_data); 171 if (ret) 172 return ret; 173 if (retlen != sect_size) 174 return -EIO; 175 176 mtdblk->cache_offset = sect_start; 177 mtdblk->cache_size = sect_size; 178 mtdblk->cache_state = STATE_CLEAN; 179 } 180 181 /* write data to our local cache */ 182 memcpy (mtdblk->cache_data + offset, buf, size); 183 mtdblk->cache_state = STATE_DIRTY; 184 } 185 186 buf += size; 187 pos += size; 188 len -= size; 189 } 190 191 return 0; 192 } 193 194 195 static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos, 196 int len, char *buf) 197 { 198 struct mtd_info *mtd = mtdblk->mtd; 199 unsigned int sect_size = mtdblk->cache_size; 200 size_t retlen; 201 int ret; 202 203 DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n", 204 mtd->name, pos, len); 205 206 if (!sect_size) 207 return MTD_READ (mtd, pos, len, &retlen, buf); 208 209 while (len > 0) { 210 unsigned long sect_start = (pos/sect_size)*sect_size; 211 unsigned int offset = pos - sect_start; 212 unsigned int size = sect_size - offset; 213 if (size > len) 214 size = len; 215 216 /* 217 * Check if the requested data is already cached 218 * Read the requested amount of data from our internal cache if it 219 * contains what we want, otherwise we read the data directly 220 * from flash. 221 */ 222 if (mtdblk->cache_state != STATE_EMPTY && 223 mtdblk->cache_offset == sect_start) { 224 memcpy (buf, mtdblk->cache_data + offset, size); 225 } else { 226 ret = MTD_READ (mtd, pos, size, &retlen, buf); 227 if (ret) 228 return ret; 229 if (retlen != size) 230 return -EIO; 231 } 232 233 buf += size; 234 pos += size; 235 len -= size; 236 } 237 238 return 0; 239 } 240 241 static int mtdblock_readsect(struct mtd_blktrans_dev *dev, 242 unsigned long block, char *buf) 243 { 244 struct mtdblk_dev *mtdblk = mtdblks[dev->devnum]; 245 return do_cached_read(mtdblk, block<<9, 512, buf); 246 } 247 248 static int mtdblock_writesect(struct mtd_blktrans_dev *dev, 249 unsigned long block, char *buf) 250 { 251 struct mtdblk_dev *mtdblk = mtdblks[dev->devnum]; 252 if (unlikely(!mtdblk->cache_data && mtdblk->cache_size)) { 253 mtdblk->cache_data = vmalloc(mtdblk->mtd->erasesize); 254 if (!mtdblk->cache_data) 255 return -EINTR; 256 /* -EINTR is not really correct, but it is the best match 257 * documented in man 2 write for all cases. We could also 258 * return -EAGAIN sometimes, but why bother? 259 */ 260 } 261 return do_cached_write(mtdblk, block<<9, 512, buf); 262 } 263 264 static int mtdblock_open(struct mtd_blktrans_dev *mbd) 265 { 266 struct mtdblk_dev *mtdblk; 267 struct mtd_info *mtd = mbd->mtd; 268 int dev = mbd->devnum; 269 270 DEBUG(MTD_DEBUG_LEVEL1,"mtdblock_open\n"); 271 272 if (mtdblks[dev]) { 273 mtdblks[dev]->count++; 274 return 0; 275 } 276 277 /* OK, it's not open. Create cache info for it */ 278 mtdblk = kmalloc(sizeof(struct mtdblk_dev), GFP_KERNEL); 279 if (!mtdblk) 280 return -ENOMEM; 281 282 memset(mtdblk, 0, sizeof(*mtdblk)); 283 mtdblk->count = 1; 284 mtdblk->mtd = mtd; 285 286 init_MUTEX (&mtdblk->cache_sem); 287 mtdblk->cache_state = STATE_EMPTY; 288 if ((mtdblk->mtd->flags & MTD_CAP_RAM) != MTD_CAP_RAM && 289 mtdblk->mtd->erasesize) { 290 mtdblk->cache_size = mtdblk->mtd->erasesize; 291 mtdblk->cache_data = NULL; 292 } 293 294 mtdblks[dev] = mtdblk; 295 296 DEBUG(MTD_DEBUG_LEVEL1, "ok\n"); 297 298 return 0; 299 } 300 301 static int mtdblock_release(struct mtd_blktrans_dev *mbd) 302 { 303 int dev = mbd->devnum; 304 struct mtdblk_dev *mtdblk = mtdblks[dev]; 305 306 DEBUG(MTD_DEBUG_LEVEL1, "mtdblock_release\n"); 307 308 down(&mtdblk->cache_sem); 309 write_cached_data(mtdblk); 310 up(&mtdblk->cache_sem); 311 312 if (!--mtdblk->count) { 313 /* It was the last usage. Free the device */ 314 mtdblks[dev] = NULL; 315 if (mtdblk->mtd->sync) 316 mtdblk->mtd->sync(mtdblk->mtd); 317 vfree(mtdblk->cache_data); 318 kfree(mtdblk); 319 } 320 DEBUG(MTD_DEBUG_LEVEL1, "ok\n"); 321 322 return 0; 323 } 324 325 static int mtdblock_flush(struct mtd_blktrans_dev *dev) 326 { 327 struct mtdblk_dev *mtdblk = mtdblks[dev->devnum]; 328 329 down(&mtdblk->cache_sem); 330 write_cached_data(mtdblk); 331 up(&mtdblk->cache_sem); 332 333 if (mtdblk->mtd->sync) 334 mtdblk->mtd->sync(mtdblk->mtd); 335 return 0; 336 } 337 338 static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd) 339 { 340 struct mtd_blktrans_dev *dev = kmalloc(sizeof(*dev), GFP_KERNEL); 341 342 if (!dev) 343 return; 344 345 memset(dev, 0, sizeof(*dev)); 346 347 dev->mtd = mtd; 348 dev->devnum = mtd->index; 349 dev->blksize = 512; 350 dev->size = mtd->size >> 9; 351 dev->tr = tr; 352 353 if (!(mtd->flags & MTD_WRITEABLE)) 354 dev->readonly = 1; 355 356 add_mtd_blktrans_dev(dev); 357 } 358 359 static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev) 360 { 361 del_mtd_blktrans_dev(dev); 362 kfree(dev); 363 } 364 365 static struct mtd_blktrans_ops mtdblock_tr = { 366 .name = "mtdblock", 367 .major = 31, 368 .part_bits = 0, 369 .open = mtdblock_open, 370 .flush = mtdblock_flush, 371 .release = mtdblock_release, 372 .readsect = mtdblock_readsect, 373 .writesect = mtdblock_writesect, 374 .add_mtd = mtdblock_add_mtd, 375 .remove_dev = mtdblock_remove_dev, 376 .owner = THIS_MODULE, 377 }; 378 379 static int __init init_mtdblock(void) 380 { 381 return register_mtd_blktrans(&mtdblock_tr); 382 } 383 384 static void __exit cleanup_mtdblock(void) 385 { 386 deregister_mtd_blktrans(&mtdblock_tr); 387 } 388 389 module_init(init_mtdblock); 390 module_exit(cleanup_mtdblock); 391 392 393 MODULE_LICENSE("GPL"); 394 MODULE_AUTHOR("Nicolas Pitre <nico@cam.org> et al."); 395 MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices"); 396