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 23 static struct mtdblk_dev { 24 struct mtd_info *mtd; 25 int count; 26 struct semaphore cache_sem; 27 unsigned char *cache_data; 28 unsigned long cache_offset; 29 unsigned int cache_size; 30 enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state; 31 } *mtdblks[MAX_MTD_DEVICES]; 32 33 /* 34 * Cache stuff... 35 * 36 * Since typical flash erasable sectors are much larger than what Linux's 37 * buffer cache can handle, we must implement read-modify-write on flash 38 * sectors for each block write requests. To avoid over-erasing flash sectors 39 * and to speed things up, we locally cache a whole flash sector while it is 40 * being written to until a different sector is required. 41 */ 42 43 static void erase_callback(struct erase_info *done) 44 { 45 wait_queue_head_t *wait_q = (wait_queue_head_t *)done->priv; 46 wake_up(wait_q); 47 } 48 49 static int erase_write (struct mtd_info *mtd, unsigned long pos, 50 int len, const char *buf) 51 { 52 struct erase_info erase; 53 DECLARE_WAITQUEUE(wait, current); 54 wait_queue_head_t wait_q; 55 size_t retlen; 56 int ret; 57 58 /* 59 * First, let's erase the flash block. 60 */ 61 62 init_waitqueue_head(&wait_q); 63 erase.mtd = mtd; 64 erase.callback = erase_callback; 65 erase.addr = pos; 66 erase.len = len; 67 erase.priv = (u_long)&wait_q; 68 69 set_current_state(TASK_INTERRUPTIBLE); 70 add_wait_queue(&wait_q, &wait); 71 72 ret = MTD_ERASE(mtd, &erase); 73 if (ret) { 74 set_current_state(TASK_RUNNING); 75 remove_wait_queue(&wait_q, &wait); 76 printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] " 77 "on \"%s\" failed\n", 78 pos, len, mtd->name); 79 return ret; 80 } 81 82 schedule(); /* Wait for erase to finish. */ 83 remove_wait_queue(&wait_q, &wait); 84 85 /* 86 * Next, writhe data to flash. 87 */ 88 89 ret = MTD_WRITE (mtd, pos, len, &retlen, buf); 90 if (ret) 91 return ret; 92 if (retlen != len) 93 return -EIO; 94 return 0; 95 } 96 97 98 static int write_cached_data (struct mtdblk_dev *mtdblk) 99 { 100 struct mtd_info *mtd = mtdblk->mtd; 101 int ret; 102 103 if (mtdblk->cache_state != STATE_DIRTY) 104 return 0; 105 106 DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: writing cached data for \"%s\" " 107 "at 0x%lx, size 0x%x\n", mtd->name, 108 mtdblk->cache_offset, mtdblk->cache_size); 109 110 ret = erase_write (mtd, mtdblk->cache_offset, 111 mtdblk->cache_size, mtdblk->cache_data); 112 if (ret) 113 return ret; 114 115 /* 116 * Here we could argubly set the cache state to STATE_CLEAN. 117 * However this could lead to inconsistency since we will not 118 * be notified if this content is altered on the flash by other 119 * means. Let's declare it empty and leave buffering tasks to 120 * the buffer cache instead. 121 */ 122 mtdblk->cache_state = STATE_EMPTY; 123 return 0; 124 } 125 126 127 static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos, 128 int len, const char *buf) 129 { 130 struct mtd_info *mtd = mtdblk->mtd; 131 unsigned int sect_size = mtdblk->cache_size; 132 size_t retlen; 133 int ret; 134 135 DEBUG(MTD_DEBUG_LEVEL2, "mtdblock: write on \"%s\" at 0x%lx, size 0x%x\n", 136 mtd->name, pos, len); 137 138 if (!sect_size) 139 return MTD_WRITE (mtd, pos, len, &retlen, buf); 140 141 while (len > 0) { 142 unsigned long sect_start = (pos/sect_size)*sect_size; 143 unsigned int offset = pos - sect_start; 144 unsigned int size = sect_size - offset; 145 if( size > len ) 146 size = len; 147 148 if (size == sect_size) { 149 /* 150 * We are covering a whole sector. Thus there is no 151 * need to bother with the cache while it may still be 152 * useful for other partial writes. 153 */ 154 ret = erase_write (mtd, pos, size, buf); 155 if (ret) 156 return ret; 157 } else { 158 /* Partial sector: need to use the cache */ 159 160 if (mtdblk->cache_state == STATE_DIRTY && 161 mtdblk->cache_offset != sect_start) { 162 ret = write_cached_data(mtdblk); 163 if (ret) 164 return ret; 165 } 166 167 if (mtdblk->cache_state == STATE_EMPTY || 168 mtdblk->cache_offset != sect_start) { 169 /* fill the cache with the current sector */ 170 mtdblk->cache_state = STATE_EMPTY; 171 ret = MTD_READ(mtd, sect_start, sect_size, &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 = kmalloc(sizeof(struct mtdblk_dev), GFP_KERNEL); 280 if (!mtdblk) 281 return -ENOMEM; 282 283 memset(mtdblk, 0, sizeof(*mtdblk)); 284 mtdblk->count = 1; 285 mtdblk->mtd = mtd; 286 287 init_MUTEX (&mtdblk->cache_sem); 288 mtdblk->cache_state = STATE_EMPTY; 289 if ((mtdblk->mtd->flags & MTD_CAP_RAM) != MTD_CAP_RAM && 290 mtdblk->mtd->erasesize) { 291 mtdblk->cache_size = mtdblk->mtd->erasesize; 292 mtdblk->cache_data = NULL; 293 } 294 295 mtdblks[dev] = mtdblk; 296 297 DEBUG(MTD_DEBUG_LEVEL1, "ok\n"); 298 299 return 0; 300 } 301 302 static int mtdblock_release(struct mtd_blktrans_dev *mbd) 303 { 304 int dev = mbd->devnum; 305 struct mtdblk_dev *mtdblk = mtdblks[dev]; 306 307 DEBUG(MTD_DEBUG_LEVEL1, "mtdblock_release\n"); 308 309 down(&mtdblk->cache_sem); 310 write_cached_data(mtdblk); 311 up(&mtdblk->cache_sem); 312 313 if (!--mtdblk->count) { 314 /* It was the last usage. Free the device */ 315 mtdblks[dev] = NULL; 316 if (mtdblk->mtd->sync) 317 mtdblk->mtd->sync(mtdblk->mtd); 318 vfree(mtdblk->cache_data); 319 kfree(mtdblk); 320 } 321 DEBUG(MTD_DEBUG_LEVEL1, "ok\n"); 322 323 return 0; 324 } 325 326 static int mtdblock_flush(struct mtd_blktrans_dev *dev) 327 { 328 struct mtdblk_dev *mtdblk = mtdblks[dev->devnum]; 329 330 down(&mtdblk->cache_sem); 331 write_cached_data(mtdblk); 332 up(&mtdblk->cache_sem); 333 334 if (mtdblk->mtd->sync) 335 mtdblk->mtd->sync(mtdblk->mtd); 336 return 0; 337 } 338 339 static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd) 340 { 341 struct mtd_blktrans_dev *dev = kmalloc(sizeof(*dev), GFP_KERNEL); 342 343 if (!dev) 344 return; 345 346 memset(dev, 0, sizeof(*dev)); 347 348 dev->mtd = mtd; 349 dev->devnum = mtd->index; 350 dev->blksize = 512; 351 dev->size = mtd->size >> 9; 352 dev->tr = tr; 353 354 if (!(mtd->flags & MTD_WRITEABLE)) 355 dev->readonly = 1; 356 357 add_mtd_blktrans_dev(dev); 358 } 359 360 static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev) 361 { 362 del_mtd_blktrans_dev(dev); 363 kfree(dev); 364 } 365 366 static struct mtd_blktrans_ops mtdblock_tr = { 367 .name = "mtdblock", 368 .major = 31, 369 .part_bits = 0, 370 .open = mtdblock_open, 371 .flush = mtdblock_flush, 372 .release = mtdblock_release, 373 .readsect = mtdblock_readsect, 374 .writesect = mtdblock_writesect, 375 .add_mtd = mtdblock_add_mtd, 376 .remove_dev = mtdblock_remove_dev, 377 .owner = THIS_MODULE, 378 }; 379 380 static int __init init_mtdblock(void) 381 { 382 return register_mtd_blktrans(&mtdblock_tr); 383 } 384 385 static void __exit cleanup_mtdblock(void) 386 { 387 deregister_mtd_blktrans(&mtdblock_tr); 388 } 389 390 module_init(init_mtdblock); 391 module_exit(cleanup_mtdblock); 392 393 394 MODULE_LICENSE("GPL"); 395 MODULE_AUTHOR("Nicolas Pitre <nico@cam.org> et al."); 396 MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices"); 397