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