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 /* 49 * Cache stuff... 50 * 51 * Since typical flash erasable sectors are much larger than what Linux's 52 * buffer cache can handle, we must implement read-modify-write on flash 53 * sectors for each block write requests. To avoid over-erasing flash sectors 54 * and to speed things up, we locally cache a whole flash sector while it is 55 * being written to until a different sector is required. 56 */ 57 58 static void erase_callback(struct erase_info *done) 59 { 60 wait_queue_head_t *wait_q = (wait_queue_head_t *)done->priv; 61 wake_up(wait_q); 62 } 63 64 static int erase_write (struct mtd_info *mtd, unsigned long pos, 65 int len, const char *buf) 66 { 67 struct erase_info erase; 68 DECLARE_WAITQUEUE(wait, current); 69 wait_queue_head_t wait_q; 70 size_t retlen; 71 int ret; 72 73 /* 74 * First, let's erase the flash block. 75 */ 76 77 init_waitqueue_head(&wait_q); 78 erase.mtd = mtd; 79 erase.callback = erase_callback; 80 erase.addr = pos; 81 erase.len = len; 82 erase.priv = (u_long)&wait_q; 83 84 set_current_state(TASK_INTERRUPTIBLE); 85 add_wait_queue(&wait_q, &wait); 86 87 ret = mtd_erase(mtd, &erase); 88 if (ret) { 89 set_current_state(TASK_RUNNING); 90 remove_wait_queue(&wait_q, &wait); 91 printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] " 92 "on \"%s\" failed\n", 93 pos, len, mtd->name); 94 return ret; 95 } 96 97 schedule(); /* Wait for erase to finish. */ 98 remove_wait_queue(&wait_q, &wait); 99 100 /* 101 * Next, write the data to flash. 102 */ 103 104 ret = mtd_write(mtd, pos, len, &retlen, buf); 105 if (ret) 106 return ret; 107 if (retlen != len) 108 return -EIO; 109 return 0; 110 } 111 112 113 static int write_cached_data (struct mtdblk_dev *mtdblk) 114 { 115 struct mtd_info *mtd = mtdblk->mbd.mtd; 116 int ret; 117 118 if (mtdblk->cache_state != STATE_DIRTY) 119 return 0; 120 121 pr_debug("mtdblock: writing cached data for \"%s\" " 122 "at 0x%lx, size 0x%x\n", mtd->name, 123 mtdblk->cache_offset, mtdblk->cache_size); 124 125 ret = erase_write (mtd, mtdblk->cache_offset, 126 mtdblk->cache_size, mtdblk->cache_data); 127 if (ret) 128 return ret; 129 130 /* 131 * Here we could arguably set the cache state to STATE_CLEAN. 132 * However this could lead to inconsistency since we will not 133 * be notified if this content is altered on the flash by other 134 * means. Let's declare it empty and leave buffering tasks to 135 * the buffer cache instead. 136 */ 137 mtdblk->cache_state = STATE_EMPTY; 138 return 0; 139 } 140 141 142 static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos, 143 int len, const char *buf) 144 { 145 struct mtd_info *mtd = mtdblk->mbd.mtd; 146 unsigned int sect_size = mtdblk->cache_size; 147 size_t retlen; 148 int ret; 149 150 pr_debug("mtdblock: write on \"%s\" at 0x%lx, size 0x%x\n", 151 mtd->name, pos, len); 152 153 if (!sect_size) 154 return mtd_write(mtd, pos, len, &retlen, buf); 155 156 while (len > 0) { 157 unsigned long sect_start = (pos/sect_size)*sect_size; 158 unsigned int offset = pos - sect_start; 159 unsigned int size = sect_size - offset; 160 if( size > len ) 161 size = len; 162 163 if (size == sect_size) { 164 /* 165 * We are covering a whole sector. Thus there is no 166 * need to bother with the cache while it may still be 167 * useful for other partial writes. 168 */ 169 ret = erase_write (mtd, pos, size, buf); 170 if (ret) 171 return ret; 172 } else { 173 /* Partial sector: need to use the cache */ 174 175 if (mtdblk->cache_state == STATE_DIRTY && 176 mtdblk->cache_offset != sect_start) { 177 ret = write_cached_data(mtdblk); 178 if (ret) 179 return ret; 180 } 181 182 if (mtdblk->cache_state == STATE_EMPTY || 183 mtdblk->cache_offset != sect_start) { 184 /* fill the cache with the current sector */ 185 mtdblk->cache_state = STATE_EMPTY; 186 ret = mtd_read(mtd, sect_start, sect_size, 187 &retlen, mtdblk->cache_data); 188 if (ret) 189 return ret; 190 if (retlen != sect_size) 191 return -EIO; 192 193 mtdblk->cache_offset = sect_start; 194 mtdblk->cache_size = sect_size; 195 mtdblk->cache_state = STATE_CLEAN; 196 } 197 198 /* write data to our local cache */ 199 memcpy (mtdblk->cache_data + offset, buf, size); 200 mtdblk->cache_state = STATE_DIRTY; 201 } 202 203 buf += size; 204 pos += size; 205 len -= size; 206 } 207 208 return 0; 209 } 210 211 212 static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos, 213 int len, char *buf) 214 { 215 struct mtd_info *mtd = mtdblk->mbd.mtd; 216 unsigned int sect_size = mtdblk->cache_size; 217 size_t retlen; 218 int ret; 219 220 pr_debug("mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n", 221 mtd->name, pos, len); 222 223 if (!sect_size) 224 return mtd_read(mtd, pos, len, &retlen, buf); 225 226 while (len > 0) { 227 unsigned long sect_start = (pos/sect_size)*sect_size; 228 unsigned int offset = pos - sect_start; 229 unsigned int size = sect_size - offset; 230 if (size > len) 231 size = len; 232 233 /* 234 * Check if the requested data is already cached 235 * Read the requested amount of data from our internal cache if it 236 * contains what we want, otherwise we read the data directly 237 * from flash. 238 */ 239 if (mtdblk->cache_state != STATE_EMPTY && 240 mtdblk->cache_offset == sect_start) { 241 memcpy (buf, mtdblk->cache_data + offset, size); 242 } else { 243 ret = mtd_read(mtd, pos, size, &retlen, buf); 244 if (ret) 245 return ret; 246 if (retlen != size) 247 return -EIO; 248 } 249 250 buf += size; 251 pos += size; 252 len -= size; 253 } 254 255 return 0; 256 } 257 258 static int mtdblock_readsect(struct mtd_blktrans_dev *dev, 259 unsigned long block, char *buf) 260 { 261 struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd); 262 return do_cached_read(mtdblk, block<<9, 512, buf); 263 } 264 265 static int mtdblock_writesect(struct mtd_blktrans_dev *dev, 266 unsigned long block, char *buf) 267 { 268 struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd); 269 if (unlikely(!mtdblk->cache_data && mtdblk->cache_size)) { 270 mtdblk->cache_data = vmalloc(mtdblk->mbd.mtd->erasesize); 271 if (!mtdblk->cache_data) 272 return -EINTR; 273 /* -EINTR is not really correct, but it is the best match 274 * documented in man 2 write for all cases. We could also 275 * return -EAGAIN sometimes, but why bother? 276 */ 277 } 278 return do_cached_write(mtdblk, block<<9, 512, buf); 279 } 280 281 static int mtdblock_open(struct mtd_blktrans_dev *mbd) 282 { 283 struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd); 284 285 pr_debug("mtdblock_open\n"); 286 287 if (mtdblk->count) { 288 mtdblk->count++; 289 return 0; 290 } 291 292 /* OK, it's not open. Create cache info for it */ 293 mtdblk->count = 1; 294 mutex_init(&mtdblk->cache_mutex); 295 mtdblk->cache_state = STATE_EMPTY; 296 if (!(mbd->mtd->flags & MTD_NO_ERASE) && mbd->mtd->erasesize) { 297 mtdblk->cache_size = mbd->mtd->erasesize; 298 mtdblk->cache_data = NULL; 299 } 300 301 pr_debug("ok\n"); 302 303 return 0; 304 } 305 306 static void mtdblock_release(struct mtd_blktrans_dev *mbd) 307 { 308 struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd); 309 310 pr_debug("mtdblock_release\n"); 311 312 mutex_lock(&mtdblk->cache_mutex); 313 write_cached_data(mtdblk); 314 mutex_unlock(&mtdblk->cache_mutex); 315 316 if (!--mtdblk->count) { 317 /* 318 * It was the last usage. Free the cache, but only sync if 319 * opened for writing. 320 */ 321 if (mbd->file_mode & FMODE_WRITE) 322 mtd_sync(mbd->mtd); 323 vfree(mtdblk->cache_data); 324 } 325 326 pr_debug("ok\n"); 327 } 328 329 static int mtdblock_flush(struct mtd_blktrans_dev *dev) 330 { 331 struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd); 332 333 mutex_lock(&mtdblk->cache_mutex); 334 write_cached_data(mtdblk); 335 mutex_unlock(&mtdblk->cache_mutex); 336 mtd_sync(dev->mtd); 337 return 0; 338 } 339 340 static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd) 341 { 342 struct mtdblk_dev *dev = kzalloc(sizeof(*dev), GFP_KERNEL); 343 344 if (!dev) 345 return; 346 347 dev->mbd.mtd = mtd; 348 dev->mbd.devnum = mtd->index; 349 350 dev->mbd.size = mtd->size >> 9; 351 dev->mbd.tr = tr; 352 353 if (!(mtd->flags & MTD_WRITEABLE)) 354 dev->mbd.readonly = 1; 355 356 if (add_mtd_blktrans_dev(&dev->mbd)) 357 kfree(dev); 358 } 359 360 static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev) 361 { 362 del_mtd_blktrans_dev(dev); 363 } 364 365 static struct mtd_blktrans_ops mtdblock_tr = { 366 .name = "mtdblock", 367 .major = MTD_BLOCK_MAJOR, 368 .part_bits = 0, 369 .blksize = 512, 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@fluxnic.net> et al."); 396 MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices"); 397