2 * block2mtd.c - create an mtd from a block device
4 * Copyright (C) 2001,2002 Simon Evans <spse@secret.org.uk>
5 * Copyright (C) 2004-2006 Joern Engel <joern@wh.fh-wedel.de>
10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13 * When the first attempt at device initialization fails, we may need to
14 * wait a little bit and retry. This timeout, by default 3 seconds, gives
15 * device time to start up. Required on BCM2708 and a few other chipsets.
17 #define MTD_DEFAULT_TIMEOUT 3
19 #include <linux/module.h>
20 #include <linux/delay.h>
22 #include <linux/blkdev.h>
23 #include <linux/backing-dev.h>
24 #include <linux/bio.h>
25 #include <linux/pagemap.h>
26 #include <linux/list.h>
27 #include <linux/init.h>
28 #include <linux/mtd/mtd.h>
29 #include <linux/mutex.h>
30 #include <linux/mount.h>
31 #include <linux/slab.h>
32 #include <linux/major.h>
34 /* Info for the block device */
35 struct block2mtd_dev {
36 struct list_head list;
37 struct block_device *blkdev;
39 struct mutex write_mutex;
43 /* Static info about the MTD, used in cleanup_module */
44 static LIST_HEAD(blkmtd_device_list);
47 static struct page *page_read(struct address_space *mapping, int index)
49 return read_mapping_page(mapping, index, NULL);
52 /* erase a specified part of the device */
53 static int _block2mtd_erase(struct block2mtd_dev *dev, loff_t to, size_t len)
55 struct address_space *mapping = dev->blkdev->bd_inode->i_mapping;
57 int index = to >> PAGE_SHIFT; // page index
58 int pages = len >> PAGE_SHIFT;
63 page = page_read(mapping, index);
67 max = page_address(page) + PAGE_SIZE;
68 for (p=page_address(page); p<max; p++)
71 memset(page_address(page), 0xff, PAGE_SIZE);
74 balance_dirty_pages_ratelimited(mapping);
84 static int block2mtd_erase(struct mtd_info *mtd, struct erase_info *instr)
86 struct block2mtd_dev *dev = mtd->priv;
87 size_t from = instr->addr;
88 size_t len = instr->len;
91 instr->state = MTD_ERASING;
92 mutex_lock(&dev->write_mutex);
93 err = _block2mtd_erase(dev, from, len);
94 mutex_unlock(&dev->write_mutex);
96 pr_err("erase failed err = %d\n", err);
97 instr->state = MTD_ERASE_FAILED;
99 instr->state = MTD_ERASE_DONE;
101 mtd_erase_callback(instr);
106 static int block2mtd_read(struct mtd_info *mtd, loff_t from, size_t len,
107 size_t *retlen, u_char *buf)
109 struct block2mtd_dev *dev = mtd->priv;
111 int index = from >> PAGE_SHIFT;
112 int offset = from & (PAGE_SIZE-1);
116 if ((offset + len) > PAGE_SIZE)
117 cpylen = PAGE_SIZE - offset; // multiple pages
119 cpylen = len; // this page
122 page = page_read(dev->blkdev->bd_inode->i_mapping, index);
124 return PTR_ERR(page);
126 memcpy(buf, page_address(page) + offset, cpylen);
139 /* write data to the underlying device */
140 static int _block2mtd_write(struct block2mtd_dev *dev, const u_char *buf,
141 loff_t to, size_t len, size_t *retlen)
144 struct address_space *mapping = dev->blkdev->bd_inode->i_mapping;
145 int index = to >> PAGE_SHIFT; // page index
146 int offset = to & ~PAGE_MASK; // page offset
150 if ((offset+len) > PAGE_SIZE)
151 cpylen = PAGE_SIZE - offset; // multiple pages
153 cpylen = len; // this page
156 page = page_read(mapping, index);
158 return PTR_ERR(page);
160 if (memcmp(page_address(page)+offset, buf, cpylen)) {
162 memcpy(page_address(page) + offset, buf, cpylen);
163 set_page_dirty(page);
165 balance_dirty_pages_ratelimited(mapping);
180 static int block2mtd_write(struct mtd_info *mtd, loff_t to, size_t len,
181 size_t *retlen, const u_char *buf)
183 struct block2mtd_dev *dev = mtd->priv;
186 mutex_lock(&dev->write_mutex);
187 err = _block2mtd_write(dev, buf, to, len, retlen);
188 mutex_unlock(&dev->write_mutex);
195 /* sync the device - wait until the write queue is empty */
196 static void block2mtd_sync(struct mtd_info *mtd)
198 struct block2mtd_dev *dev = mtd->priv;
199 sync_blockdev(dev->blkdev);
204 static void block2mtd_free_device(struct block2mtd_dev *dev)
209 kfree(dev->mtd.name);
212 invalidate_mapping_pages(dev->blkdev->bd_inode->i_mapping,
214 blkdev_put(dev->blkdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
221 static struct block2mtd_dev *add_device(char *devname, int erase_size,
227 const fmode_t mode = FMODE_READ | FMODE_WRITE | FMODE_EXCL;
228 struct block_device *bdev = ERR_PTR(-ENODEV);
229 struct block2mtd_dev *dev;
235 dev = kzalloc(sizeof(struct block2mtd_dev), GFP_KERNEL);
239 /* Get a handle on the device */
240 bdev = blkdev_get_by_path(devname, mode, dev);
244 * We might not have the root device mounted at this point.
245 * Try to resolve the device name by other means.
247 for (i = 0; IS_ERR(bdev) && i <= timeout; i++) {
252 * Calling wait_for_device_probe in the first loop
253 * was not enough, sleep for a bit in subsequent
257 wait_for_device_probe();
259 devt = name_to_dev_t(devname);
262 bdev = blkdev_get_by_dev(devt, mode, dev);
267 pr_err("error: cannot open device %s\n", devname);
268 goto err_free_block2mtd;
272 if (MAJOR(bdev->bd_dev) == MTD_BLOCK_MAJOR) {
273 pr_err("attempting to use an MTD device as a block device\n");
274 goto err_free_block2mtd;
277 if ((long)dev->blkdev->bd_inode->i_size % erase_size) {
278 pr_err("erasesize must be a divisor of device size\n");
279 goto err_free_block2mtd;
282 mutex_init(&dev->write_mutex);
284 /* Setup the MTD structure */
285 /* make the name contain the block device in */
286 name = kasprintf(GFP_KERNEL, "block2mtd: %s", devname);
288 goto err_destroy_mutex;
290 dev->mtd.name = name;
292 dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
293 dev->mtd.erasesize = erase_size;
294 dev->mtd.writesize = 1;
295 dev->mtd.writebufsize = PAGE_SIZE;
296 dev->mtd.type = MTD_RAM;
297 dev->mtd.flags = MTD_CAP_RAM;
298 dev->mtd._erase = block2mtd_erase;
299 dev->mtd._write = block2mtd_write;
300 dev->mtd._sync = block2mtd_sync;
301 dev->mtd._read = block2mtd_read;
303 dev->mtd.owner = THIS_MODULE;
305 if (mtd_device_register(&dev->mtd, NULL, 0)) {
306 /* Device didn't get added, so free the entry */
307 goto err_destroy_mutex;
310 list_add(&dev->list, &blkmtd_device_list);
311 pr_info("mtd%d: [%s] erase_size = %dKiB [%d]\n",
313 dev->mtd.name + strlen("block2mtd: "),
314 dev->mtd.erasesize >> 10, dev->mtd.erasesize);
318 mutex_destroy(&dev->write_mutex);
320 block2mtd_free_device(dev);
325 /* This function works similar to reguler strtoul. In addition, it
326 * allows some suffixes for a more human-readable number format:
327 * ki, Ki, kiB, KiB - multiply result with 1024
328 * Mi, MiB - multiply result with 1024^2
329 * Gi, GiB - multiply result with 1024^3
331 static int ustrtoul(const char *cp, char **endp, unsigned int base)
333 unsigned long result = simple_strtoul(cp, endp, base);
342 /* By dwmw2 editorial decree, "ki", "Mi" or "Gi" are to be used. */
343 if ((*endp)[1] == 'i') {
344 if ((*endp)[2] == 'B')
354 static int parse_num(size_t *num, const char *token)
359 n = (size_t) ustrtoul(token, &endp, 0);
368 static inline void kill_final_newline(char *str)
370 char *newline = strrchr(str, '\n');
371 if (newline && !newline[1])
377 static int block2mtd_init_called = 0;
378 /* 80 for device, 12 for erase size */
379 static char block2mtd_paramline[80 + 12];
382 static int block2mtd_setup2(const char *val)
384 /* 80 for device, 12 for erase size, 80 for name, 8 for timeout */
385 char buf[80 + 12 + 80 + 8];
389 size_t erase_size = PAGE_SIZE;
390 unsigned long timeout = MTD_DEFAULT_TIMEOUT;
393 if (strnlen(val, sizeof(buf)) >= sizeof(buf)) {
394 pr_err("parameter too long\n");
399 kill_final_newline(str);
401 for (i = 0; i < 2; i++)
402 token[i] = strsep(&str, ",");
405 pr_err("too many arguments\n");
410 pr_err("no argument\n");
415 if (strlen(name) + 1 > 80) {
416 pr_err("device name too long\n");
421 ret = parse_num(&erase_size, token[1]);
423 pr_err("illegal erase size\n");
428 add_device(name, erase_size, timeout);
434 static int block2mtd_setup(const char *val, struct kernel_param *kp)
437 return block2mtd_setup2(val);
439 /* If more parameters are later passed in via
440 /sys/module/block2mtd/parameters/block2mtd
441 and block2mtd_init() has already been called,
442 we can parse the argument now. */
444 if (block2mtd_init_called)
445 return block2mtd_setup2(val);
447 /* During early boot stage, we only save the parameters
448 here. We must parse them later: if the param passed
449 from kernel boot command line, block2mtd_setup() is
450 called so early that it is not possible to resolve
451 the device (even kmalloc() fails). Deter that work to
452 block2mtd_setup2(). */
454 strlcpy(block2mtd_paramline, val, sizeof(block2mtd_paramline));
461 module_param_call(block2mtd, block2mtd_setup, NULL, NULL, 0200);
462 MODULE_PARM_DESC(block2mtd, "Device to use. \"block2mtd=<dev>[,<erasesize>]\"");
464 static int __init block2mtd_init(void)
469 if (strlen(block2mtd_paramline))
470 ret = block2mtd_setup2(block2mtd_paramline);
471 block2mtd_init_called = 1;
478 static void block2mtd_exit(void)
480 struct list_head *pos, *next;
482 /* Remove the MTD devices */
483 list_for_each_safe(pos, next, &blkmtd_device_list) {
484 struct block2mtd_dev *dev = list_entry(pos, typeof(*dev), list);
485 block2mtd_sync(&dev->mtd);
486 mtd_device_unregister(&dev->mtd);
487 mutex_destroy(&dev->write_mutex);
488 pr_info("mtd%d: [%s] removed\n",
490 dev->mtd.name + strlen("block2mtd: "));
491 list_del(&dev->list);
492 block2mtd_free_device(dev);
496 late_initcall(block2mtd_init);
497 module_exit(block2mtd_exit);
499 MODULE_LICENSE("GPL");
500 MODULE_AUTHOR("Joern Engel <joern@lazybastard.org>");
501 MODULE_DESCRIPTION("Emulate an MTD using a block device");