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 int erase_write (struct mtd_info *mtd, unsigned long pos, 59 unsigned int len, const char *buf) 60 { 61 struct erase_info erase; 62 size_t retlen; 63 int ret; 64 65 /* 66 * First, let's erase the flash block. 67 */ 68 erase.addr = pos; 69 erase.len = len; 70 71 ret = mtd_erase(mtd, &erase); 72 if (ret) { 73 printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] " 74 "on \"%s\" failed\n", 75 pos, len, mtd->name); 76 return ret; 77 } 78 79 /* 80 * Next, write the data to flash. 81 */ 82 83 ret = mtd_write(mtd, pos, len, &retlen, buf); 84 if (ret) 85 return ret; 86 if (retlen != len) 87 return -EIO; 88 return 0; 89 } 90 91 92 static int write_cached_data (struct mtdblk_dev *mtdblk) 93 { 94 struct mtd_info *mtd = mtdblk->mbd.mtd; 95 int ret; 96 97 if (mtdblk->cache_state != STATE_DIRTY) 98 return 0; 99 100 pr_debug("mtdblock: writing cached data for \"%s\" " 101 "at 0x%lx, size 0x%x\n", mtd->name, 102 mtdblk->cache_offset, mtdblk->cache_size); 103 104 ret = erase_write (mtd, mtdblk->cache_offset, 105 mtdblk->cache_size, mtdblk->cache_data); 106 if (ret) 107 return ret; 108 109 /* 110 * Here we could arguably set the cache state to STATE_CLEAN. 111 * However this could lead to inconsistency since we will not 112 * be notified if this content is altered on the flash by other 113 * means. Let's declare it empty and leave buffering tasks to 114 * the buffer cache instead. 115 */ 116 mtdblk->cache_state = STATE_EMPTY; 117 return 0; 118 } 119 120 121 static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos, 122 int len, const char *buf) 123 { 124 struct mtd_info *mtd = mtdblk->mbd.mtd; 125 unsigned int sect_size = mtdblk->cache_size; 126 size_t retlen; 127 int ret; 128 129 pr_debug("mtdblock: write on \"%s\" at 0x%lx, size 0x%x\n", 130 mtd->name, pos, len); 131 132 if (!sect_size) 133 return mtd_write(mtd, pos, len, &retlen, buf); 134 135 while (len > 0) { 136 unsigned long sect_start = (pos/sect_size)*sect_size; 137 unsigned int offset = pos - sect_start; 138 unsigned int size = sect_size - offset; 139 if( size > len ) 140 size = len; 141 142 if (size == sect_size) { 143 /* 144 * We are covering a whole sector. Thus there is no 145 * need to bother with the cache while it may still be 146 * useful for other partial writes. 147 */ 148 ret = erase_write (mtd, pos, size, buf); 149 if (ret) 150 return ret; 151 } else { 152 /* Partial sector: need to use the cache */ 153 154 if (mtdblk->cache_state == STATE_DIRTY && 155 mtdblk->cache_offset != sect_start) { 156 ret = write_cached_data(mtdblk); 157 if (ret) 158 return ret; 159 } 160 161 if (mtdblk->cache_state == STATE_EMPTY || 162 mtdblk->cache_offset != sect_start) { 163 /* fill the cache with the current sector */ 164 mtdblk->cache_state = STATE_EMPTY; 165 ret = mtd_read(mtd, sect_start, sect_size, 166 &retlen, mtdblk->cache_data); 167 if (ret) 168 return ret; 169 if (retlen != sect_size) 170 return -EIO; 171 172 mtdblk->cache_offset = sect_start; 173 mtdblk->cache_size = sect_size; 174 mtdblk->cache_state = STATE_CLEAN; 175 } 176 177 /* write data to our local cache */ 178 memcpy (mtdblk->cache_data + offset, buf, size); 179 mtdblk->cache_state = STATE_DIRTY; 180 } 181 182 buf += size; 183 pos += size; 184 len -= size; 185 } 186 187 return 0; 188 } 189 190 191 static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos, 192 int len, char *buf) 193 { 194 struct mtd_info *mtd = mtdblk->mbd.mtd; 195 unsigned int sect_size = mtdblk->cache_size; 196 size_t retlen; 197 int ret; 198 199 pr_debug("mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n", 200 mtd->name, pos, len); 201 202 if (!sect_size) 203 return mtd_read(mtd, pos, len, &retlen, buf); 204 205 while (len > 0) { 206 unsigned long sect_start = (pos/sect_size)*sect_size; 207 unsigned int offset = pos - sect_start; 208 unsigned int size = sect_size - offset; 209 if (size > len) 210 size = len; 211 212 /* 213 * Check if the requested data is already cached 214 * Read the requested amount of data from our internal cache if it 215 * contains what we want, otherwise we read the data directly 216 * from flash. 217 */ 218 if (mtdblk->cache_state != STATE_EMPTY && 219 mtdblk->cache_offset == sect_start) { 220 memcpy (buf, mtdblk->cache_data + offset, size); 221 } else { 222 ret = mtd_read(mtd, pos, size, &retlen, buf); 223 if (ret) 224 return ret; 225 if (retlen != size) 226 return -EIO; 227 } 228 229 buf += size; 230 pos += size; 231 len -= size; 232 } 233 234 return 0; 235 } 236 237 static int mtdblock_readsect(struct mtd_blktrans_dev *dev, 238 unsigned long block, char *buf) 239 { 240 struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd); 241 return do_cached_read(mtdblk, block<<9, 512, buf); 242 } 243 244 static int mtdblock_writesect(struct mtd_blktrans_dev *dev, 245 unsigned long block, char *buf) 246 { 247 struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd); 248 if (unlikely(!mtdblk->cache_data && mtdblk->cache_size)) { 249 mtdblk->cache_data = vmalloc(mtdblk->mbd.mtd->erasesize); 250 if (!mtdblk->cache_data) 251 return -EINTR; 252 /* -EINTR is not really correct, but it is the best match 253 * documented in man 2 write for all cases. We could also 254 * return -EAGAIN sometimes, but why bother? 255 */ 256 } 257 return do_cached_write(mtdblk, block<<9, 512, buf); 258 } 259 260 static int mtdblock_open(struct mtd_blktrans_dev *mbd) 261 { 262 struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd); 263 264 pr_debug("mtdblock_open\n"); 265 266 if (mtdblk->count) { 267 mtdblk->count++; 268 return 0; 269 } 270 271 /* OK, it's not open. Create cache info for it */ 272 mtdblk->count = 1; 273 mutex_init(&mtdblk->cache_mutex); 274 mtdblk->cache_state = STATE_EMPTY; 275 if (!(mbd->mtd->flags & MTD_NO_ERASE) && mbd->mtd->erasesize) { 276 mtdblk->cache_size = mbd->mtd->erasesize; 277 mtdblk->cache_data = NULL; 278 } 279 280 pr_debug("ok\n"); 281 282 return 0; 283 } 284 285 static void mtdblock_release(struct mtd_blktrans_dev *mbd) 286 { 287 struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd); 288 289 pr_debug("mtdblock_release\n"); 290 291 mutex_lock(&mtdblk->cache_mutex); 292 write_cached_data(mtdblk); 293 mutex_unlock(&mtdblk->cache_mutex); 294 295 if (!--mtdblk->count) { 296 /* 297 * It was the last usage. Free the cache, but only sync if 298 * opened for writing. 299 */ 300 if (mbd->file_mode & FMODE_WRITE) 301 mtd_sync(mbd->mtd); 302 vfree(mtdblk->cache_data); 303 } 304 305 pr_debug("ok\n"); 306 } 307 308 static int mtdblock_flush(struct mtd_blktrans_dev *dev) 309 { 310 struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd); 311 312 mutex_lock(&mtdblk->cache_mutex); 313 write_cached_data(mtdblk); 314 mutex_unlock(&mtdblk->cache_mutex); 315 mtd_sync(dev->mtd); 316 return 0; 317 } 318 319 static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd) 320 { 321 struct mtdblk_dev *dev = kzalloc(sizeof(*dev), GFP_KERNEL); 322 323 if (!dev) 324 return; 325 326 dev->mbd.mtd = mtd; 327 dev->mbd.devnum = mtd->index; 328 329 dev->mbd.size = mtd->size >> 9; 330 dev->mbd.tr = tr; 331 332 if (!(mtd->flags & MTD_WRITEABLE)) 333 dev->mbd.readonly = 1; 334 335 if (add_mtd_blktrans_dev(&dev->mbd)) 336 kfree(dev); 337 } 338 339 static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev) 340 { 341 del_mtd_blktrans_dev(dev); 342 } 343 344 static struct mtd_blktrans_ops mtdblock_tr = { 345 .name = "mtdblock", 346 .major = MTD_BLOCK_MAJOR, 347 .part_bits = 0, 348 .blksize = 512, 349 .open = mtdblock_open, 350 .flush = mtdblock_flush, 351 .release = mtdblock_release, 352 .readsect = mtdblock_readsect, 353 .writesect = mtdblock_writesect, 354 .add_mtd = mtdblock_add_mtd, 355 .remove_dev = mtdblock_remove_dev, 356 .owner = THIS_MODULE, 357 }; 358 359 static int __init init_mtdblock(void) 360 { 361 return register_mtd_blktrans(&mtdblock_tr); 362 } 363 364 static void __exit cleanup_mtdblock(void) 365 { 366 deregister_mtd_blktrans(&mtdblock_tr); 367 } 368 369 module_init(init_mtdblock); 370 module_exit(cleanup_mtdblock); 371 372 373 MODULE_LICENSE("GPL"); 374 MODULE_AUTHOR("Nicolas Pitre <nico@fluxnic.net> et al."); 375 MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices"); 376