1 /* 2 * Direct MTD block device access 3 * 4 * Copyright © 1999-2010 David Woodhouse <dwmw2@infradead.org> 5 * Copyright © 2000-2003 Nicolas Pitre <nico@fluxnic.net> 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License as published by 9 * the Free Software Foundation; either version 2 of the License, or 10 * (at your option) any later version. 11 * 12 * This program is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 * GNU General Public License for more details. 16 * 17 * You should have received a copy of the GNU General Public License 18 * along with this program; if not, write to the Free Software 19 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA 20 * 21 */ 22 23 #include <linux/fs.h> 24 #include <linux/init.h> 25 #include <linux/kernel.h> 26 #include <linux/module.h> 27 #include <linux/sched.h> 28 #include <linux/slab.h> 29 #include <linux/types.h> 30 #include <linux/vmalloc.h> 31 32 #include <linux/mtd/mtd.h> 33 #include <linux/mtd/blktrans.h> 34 #include <linux/mutex.h> 35 #include <linux/major.h> 36 37 38 struct mtdblk_dev { 39 struct mtd_blktrans_dev mbd; 40 int count; 41 struct mutex cache_mutex; 42 unsigned char *cache_data; 43 unsigned long cache_offset; 44 unsigned int cache_size; 45 enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state; 46 }; 47 48 static DEFINE_MUTEX(mtdblks_lock); 49 50 /* 51 * Cache stuff... 52 * 53 * Since typical flash erasable sectors are much larger than what Linux's 54 * buffer cache can handle, we must implement read-modify-write on flash 55 * sectors for each block write requests. To avoid over-erasing flash sectors 56 * and to speed things up, we locally cache a whole flash sector while it is 57 * being written to until a different sector is required. 58 */ 59 60 static void erase_callback(struct erase_info *done) 61 { 62 wait_queue_head_t *wait_q = (wait_queue_head_t *)done->priv; 63 wake_up(wait_q); 64 } 65 66 static int erase_write (struct mtd_info *mtd, unsigned long pos, 67 int len, const char *buf) 68 { 69 struct erase_info erase; 70 DECLARE_WAITQUEUE(wait, current); 71 wait_queue_head_t wait_q; 72 size_t retlen; 73 int ret; 74 75 /* 76 * First, let's erase the flash block. 77 */ 78 79 init_waitqueue_head(&wait_q); 80 erase.mtd = mtd; 81 erase.callback = erase_callback; 82 erase.addr = pos; 83 erase.len = len; 84 erase.priv = (u_long)&wait_q; 85 86 set_current_state(TASK_INTERRUPTIBLE); 87 add_wait_queue(&wait_q, &wait); 88 89 ret = mtd_erase(mtd, &erase); 90 if (ret) { 91 set_current_state(TASK_RUNNING); 92 remove_wait_queue(&wait_q, &wait); 93 printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] " 94 "on \"%s\" failed\n", 95 pos, len, mtd->name); 96 return ret; 97 } 98 99 schedule(); /* Wait for erase to finish. */ 100 remove_wait_queue(&wait_q, &wait); 101 102 /* 103 * Next, write the data to flash. 104 */ 105 106 ret = mtd_write(mtd, pos, len, &retlen, buf); 107 if (ret) 108 return ret; 109 if (retlen != len) 110 return -EIO; 111 return 0; 112 } 113 114 115 static int write_cached_data (struct mtdblk_dev *mtdblk) 116 { 117 struct mtd_info *mtd = mtdblk->mbd.mtd; 118 int ret; 119 120 if (mtdblk->cache_state != STATE_DIRTY) 121 return 0; 122 123 pr_debug("mtdblock: writing cached data for \"%s\" " 124 "at 0x%lx, size 0x%x\n", mtd->name, 125 mtdblk->cache_offset, mtdblk->cache_size); 126 127 ret = erase_write (mtd, mtdblk->cache_offset, 128 mtdblk->cache_size, mtdblk->cache_data); 129 if (ret) 130 return ret; 131 132 /* 133 * Here we could arguably set the cache state to STATE_CLEAN. 134 * However this could lead to inconsistency since we will not 135 * be notified if this content is altered on the flash by other 136 * means. Let's declare it empty and leave buffering tasks to 137 * the buffer cache instead. 138 */ 139 mtdblk->cache_state = STATE_EMPTY; 140 return 0; 141 } 142 143 144 static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos, 145 int len, const char *buf) 146 { 147 struct mtd_info *mtd = mtdblk->mbd.mtd; 148 unsigned int sect_size = mtdblk->cache_size; 149 size_t retlen; 150 int ret; 151 152 pr_debug("mtdblock: write on \"%s\" at 0x%lx, size 0x%x\n", 153 mtd->name, pos, len); 154 155 if (!sect_size) 156 return mtd_write(mtd, pos, len, &retlen, buf); 157 158 while (len > 0) { 159 unsigned long sect_start = (pos/sect_size)*sect_size; 160 unsigned int offset = pos - sect_start; 161 unsigned int size = sect_size - offset; 162 if( size > len ) 163 size = len; 164 165 if (size == sect_size) { 166 /* 167 * We are covering a whole sector. Thus there is no 168 * need to bother with the cache while it may still be 169 * useful for other partial writes. 170 */ 171 ret = erase_write (mtd, pos, size, buf); 172 if (ret) 173 return ret; 174 } else { 175 /* Partial sector: need to use the cache */ 176 177 if (mtdblk->cache_state == STATE_DIRTY && 178 mtdblk->cache_offset != sect_start) { 179 ret = write_cached_data(mtdblk); 180 if (ret) 181 return ret; 182 } 183 184 if (mtdblk->cache_state == STATE_EMPTY || 185 mtdblk->cache_offset != sect_start) { 186 /* fill the cache with the current sector */ 187 mtdblk->cache_state = STATE_EMPTY; 188 ret = mtd_read(mtd, sect_start, sect_size, 189 &retlen, mtdblk->cache_data); 190 if (ret) 191 return ret; 192 if (retlen != sect_size) 193 return -EIO; 194 195 mtdblk->cache_offset = sect_start; 196 mtdblk->cache_size = sect_size; 197 mtdblk->cache_state = STATE_CLEAN; 198 } 199 200 /* write data to our local cache */ 201 memcpy (mtdblk->cache_data + offset, buf, size); 202 mtdblk->cache_state = STATE_DIRTY; 203 } 204 205 buf += size; 206 pos += size; 207 len -= size; 208 } 209 210 return 0; 211 } 212 213 214 static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos, 215 int len, char *buf) 216 { 217 struct mtd_info *mtd = mtdblk->mbd.mtd; 218 unsigned int sect_size = mtdblk->cache_size; 219 size_t retlen; 220 int ret; 221 222 pr_debug("mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n", 223 mtd->name, pos, len); 224 225 if (!sect_size) 226 return mtd_read(mtd, pos, len, &retlen, buf); 227 228 while (len > 0) { 229 unsigned long sect_start = (pos/sect_size)*sect_size; 230 unsigned int offset = pos - sect_start; 231 unsigned int size = sect_size - offset; 232 if (size > len) 233 size = len; 234 235 /* 236 * Check if the requested data is already cached 237 * Read the requested amount of data from our internal cache if it 238 * contains what we want, otherwise we read the data directly 239 * from flash. 240 */ 241 if (mtdblk->cache_state != STATE_EMPTY && 242 mtdblk->cache_offset == sect_start) { 243 memcpy (buf, mtdblk->cache_data + offset, size); 244 } else { 245 ret = mtd_read(mtd, pos, size, &retlen, buf); 246 if (ret) 247 return ret; 248 if (retlen != size) 249 return -EIO; 250 } 251 252 buf += size; 253 pos += size; 254 len -= size; 255 } 256 257 return 0; 258 } 259 260 static int mtdblock_readsect(struct mtd_blktrans_dev *dev, 261 unsigned long block, char *buf) 262 { 263 struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd); 264 return do_cached_read(mtdblk, block<<9, 512, buf); 265 } 266 267 static int mtdblock_writesect(struct mtd_blktrans_dev *dev, 268 unsigned long block, char *buf) 269 { 270 struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd); 271 if (unlikely(!mtdblk->cache_data && mtdblk->cache_size)) { 272 mtdblk->cache_data = vmalloc(mtdblk->mbd.mtd->erasesize); 273 if (!mtdblk->cache_data) 274 return -EINTR; 275 /* -EINTR is not really correct, but it is the best match 276 * documented in man 2 write for all cases. We could also 277 * return -EAGAIN sometimes, but why bother? 278 */ 279 } 280 return do_cached_write(mtdblk, block<<9, 512, buf); 281 } 282 283 static int mtdblock_open(struct mtd_blktrans_dev *mbd) 284 { 285 struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd); 286 287 pr_debug("mtdblock_open\n"); 288 289 mutex_lock(&mtdblks_lock); 290 if (mtdblk->count) { 291 mtdblk->count++; 292 mutex_unlock(&mtdblks_lock); 293 return 0; 294 } 295 296 /* OK, it's not open. Create cache info for it */ 297 mtdblk->count = 1; 298 mutex_init(&mtdblk->cache_mutex); 299 mtdblk->cache_state = STATE_EMPTY; 300 if (!(mbd->mtd->flags & MTD_NO_ERASE) && mbd->mtd->erasesize) { 301 mtdblk->cache_size = mbd->mtd->erasesize; 302 mtdblk->cache_data = NULL; 303 } 304 305 mutex_unlock(&mtdblks_lock); 306 307 pr_debug("ok\n"); 308 309 return 0; 310 } 311 312 static void mtdblock_release(struct mtd_blktrans_dev *mbd) 313 { 314 struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd); 315 316 pr_debug("mtdblock_release\n"); 317 318 mutex_lock(&mtdblks_lock); 319 320 mutex_lock(&mtdblk->cache_mutex); 321 write_cached_data(mtdblk); 322 mutex_unlock(&mtdblk->cache_mutex); 323 324 if (!--mtdblk->count) { 325 /* 326 * It was the last usage. Free the cache, but only sync if 327 * opened for writing. 328 */ 329 if (mbd->file_mode & FMODE_WRITE) 330 mtd_sync(mbd->mtd); 331 vfree(mtdblk->cache_data); 332 } 333 334 mutex_unlock(&mtdblks_lock); 335 336 pr_debug("ok\n"); 337 } 338 339 static int mtdblock_flush(struct mtd_blktrans_dev *dev) 340 { 341 struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd); 342 343 mutex_lock(&mtdblk->cache_mutex); 344 write_cached_data(mtdblk); 345 mutex_unlock(&mtdblk->cache_mutex); 346 mtd_sync(dev->mtd); 347 return 0; 348 } 349 350 static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd) 351 { 352 struct mtdblk_dev *dev = kzalloc(sizeof(*dev), GFP_KERNEL); 353 354 if (!dev) 355 return; 356 357 dev->mbd.mtd = mtd; 358 dev->mbd.devnum = mtd->index; 359 360 dev->mbd.size = mtd->size >> 9; 361 dev->mbd.tr = tr; 362 363 if (!(mtd->flags & MTD_WRITEABLE)) 364 dev->mbd.readonly = 1; 365 366 if (add_mtd_blktrans_dev(&dev->mbd)) 367 kfree(dev); 368 } 369 370 static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev) 371 { 372 del_mtd_blktrans_dev(dev); 373 } 374 375 static struct mtd_blktrans_ops mtdblock_tr = { 376 .name = "mtdblock", 377 .major = MTD_BLOCK_MAJOR, 378 .part_bits = 0, 379 .blksize = 512, 380 .open = mtdblock_open, 381 .flush = mtdblock_flush, 382 .release = mtdblock_release, 383 .readsect = mtdblock_readsect, 384 .writesect = mtdblock_writesect, 385 .add_mtd = mtdblock_add_mtd, 386 .remove_dev = mtdblock_remove_dev, 387 .owner = THIS_MODULE, 388 }; 389 390 static int __init init_mtdblock(void) 391 { 392 return register_mtd_blktrans(&mtdblock_tr); 393 } 394 395 static void __exit cleanup_mtdblock(void) 396 { 397 deregister_mtd_blktrans(&mtdblock_tr); 398 } 399 400 module_init(init_mtdblock); 401 module_exit(cleanup_mtdblock); 402 403 404 MODULE_LICENSE("GPL"); 405 MODULE_AUTHOR("Nicolas Pitre <nico@fluxnic.net> et al."); 406 MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices"); 407