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
38struct 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
58static 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
64static 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
113static 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
142static 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
212static 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
258static 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
265static 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
281static 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
306static 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
329static 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
340static 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
360static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
361{
362	del_mtd_blktrans_dev(dev);
363}
364
365static 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
380static int __init init_mtdblock(void)
381{
382	return register_mtd_blktrans(&mtdblock_tr);
383}
384
385static void __exit cleanup_mtdblock(void)
386{
387	deregister_mtd_blktrans(&mtdblock_tr);
388}
389
390module_init(init_mtdblock);
391module_exit(cleanup_mtdblock);
392
393
394MODULE_LICENSE("GPL");
395MODULE_AUTHOR("Nicolas Pitre <nico@fluxnic.net> et al.");
396MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices");
397