slram.c revision 9ffc93f203c18a70623f21950f1dd473c9ec48cd 
1/*======================================================================
2
3  This driver provides a method to access memory not used by the kernel
4  itself (i.e. if the kernel commandline mem=xxx is used). To actually
5  use slram at least mtdblock or mtdchar is required (for block or
6  character device access).
7
8  Usage:
9
10  if compiled as loadable module:
11    modprobe slram map=<name>,<start>,<end/offset>
12  if statically linked into the kernel use the following kernel cmd.line
13    slram=<name>,<start>,<end/offset>
14
15  <name>: name of the device that will be listed in /proc/mtd
16  <start>: start of the memory region, decimal or hex (0xabcdef)
17  <end/offset>: end of the memory region. It's possible to use +0x1234
18                to specify the offset instead of the absolute address
19
20  NOTE:
21  With slram it's only possible to map a contiguous memory region. Therefore
22  if there's a device mapped somewhere in the region specified slram will
23  fail to load (see kernel log if modprobe fails).
24
25  -
26
27  Jochen Schaeuble <psionic@psionic.de>
28
29======================================================================*/
30
31
32#include <linux/module.h>
33#include <asm/uaccess.h>
34#include <linux/types.h>
35#include <linux/kernel.h>
36#include <linux/ptrace.h>
37#include <linux/slab.h>
38#include <linux/string.h>
39#include <linux/timer.h>
40#include <linux/major.h>
41#include <linux/fs.h>
42#include <linux/ioctl.h>
43#include <linux/init.h>
44#include <asm/io.h>
45
46#include <linux/mtd/mtd.h>
47
48#define SLRAM_MAX_DEVICES_PARAMS 6		/* 3 parameters / device */
49#define SLRAM_BLK_SZ 0x4000
50
51#define T(fmt, args...) printk(KERN_DEBUG fmt, ## args)
52#define E(fmt, args...) printk(KERN_NOTICE fmt, ## args)
53
54typedef struct slram_priv {
55	u_char *start;
56	u_char *end;
57} slram_priv_t;
58
59typedef struct slram_mtd_list {
60	struct mtd_info *mtdinfo;
61	struct slram_mtd_list *next;
62} slram_mtd_list_t;
63
64#ifdef MODULE
65static char *map[SLRAM_MAX_DEVICES_PARAMS];
66
67module_param_array(map, charp, NULL, 0);
68MODULE_PARM_DESC(map, "List of memory regions to map. \"map=<name>, <start>, <length / end>\"");
69#else
70static char *map;
71#endif
72
73static slram_mtd_list_t *slram_mtdlist = NULL;
74
75static int slram_erase(struct mtd_info *, struct erase_info *);
76static int slram_point(struct mtd_info *, loff_t, size_t, size_t *, void **,
77		resource_size_t *);
78static void slram_unpoint(struct mtd_info *, loff_t, size_t);
79static int slram_read(struct mtd_info *, loff_t, size_t, size_t *, u_char *);
80static int slram_write(struct mtd_info *, loff_t, size_t, size_t *, const u_char *);
81
82static int slram_erase(struct mtd_info *mtd, struct erase_info *instr)
83{
84	slram_priv_t *priv = mtd->priv;
85
86	if (instr->addr + instr->len > mtd->size) {
87		return(-EINVAL);
88	}
89
90	memset(priv->start + instr->addr, 0xff, instr->len);
91
92	/* This'll catch a few races. Free the thing before returning :)
93	 * I don't feel at all ashamed. This kind of thing is possible anyway
94	 * with flash, but unlikely.
95	 */
96
97	instr->state = MTD_ERASE_DONE;
98
99	mtd_erase_callback(instr);
100
101	return(0);
102}
103
104static int slram_point(struct mtd_info *mtd, loff_t from, size_t len,
105		size_t *retlen, void **virt, resource_size_t *phys)
106{
107	slram_priv_t *priv = mtd->priv;
108
109	/* can we return a physical address with this driver? */
110	if (phys)
111		return -EINVAL;
112
113	if (from + len > mtd->size)
114		return -EINVAL;
115
116	*virt = priv->start + from;
117	*retlen = len;
118	return(0);
119}
120
121static void slram_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
122{
123}
124
125static int slram_read(struct mtd_info *mtd, loff_t from, size_t len,
126		size_t *retlen, u_char *buf)
127{
128	slram_priv_t *priv = mtd->priv;
129
130	if (from > mtd->size)
131		return -EINVAL;
132
133	if (from + len > mtd->size)
134		len = mtd->size - from;
135
136	memcpy(buf, priv->start + from, len);
137
138	*retlen = len;
139	return(0);
140}
141
142static int slram_write(struct mtd_info *mtd, loff_t to, size_t len,
143		size_t *retlen, const u_char *buf)
144{
145	slram_priv_t *priv = mtd->priv;
146
147	if (to + len > mtd->size)
148		return -EINVAL;
149
150	memcpy(priv->start + to, buf, len);
151
152	*retlen = len;
153	return(0);
154}
155
156/*====================================================================*/
157
158static int register_device(char *name, unsigned long start, unsigned long length)
159{
160	slram_mtd_list_t **curmtd;
161
162	curmtd = &slram_mtdlist;
163	while (*curmtd) {
164		curmtd = &(*curmtd)->next;
165	}
166
167	*curmtd = kmalloc(sizeof(slram_mtd_list_t), GFP_KERNEL);
168	if (!(*curmtd)) {
169		E("slram: Cannot allocate new MTD device.\n");
170		return(-ENOMEM);
171	}
172	(*curmtd)->mtdinfo = kzalloc(sizeof(struct mtd_info), GFP_KERNEL);
173	(*curmtd)->next = NULL;
174
175	if ((*curmtd)->mtdinfo)	{
176		(*curmtd)->mtdinfo->priv =
177			kzalloc(sizeof(slram_priv_t), GFP_KERNEL);
178
179		if (!(*curmtd)->mtdinfo->priv) {
180			kfree((*curmtd)->mtdinfo);
181			(*curmtd)->mtdinfo = NULL;
182		}
183	}
184
185	if (!(*curmtd)->mtdinfo) {
186		E("slram: Cannot allocate new MTD device.\n");
187		return(-ENOMEM);
188	}
189
190	if (!(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start =
191				ioremap(start, length))) {
192		E("slram: ioremap failed\n");
193		return -EIO;
194	}
195	((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end =
196		((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start + length;
197
198
199	(*curmtd)->mtdinfo->name = name;
200	(*curmtd)->mtdinfo->size = length;
201	(*curmtd)->mtdinfo->flags = MTD_CAP_RAM;
202        (*curmtd)->mtdinfo->erase = slram_erase;
203	(*curmtd)->mtdinfo->point = slram_point;
204	(*curmtd)->mtdinfo->unpoint = slram_unpoint;
205	(*curmtd)->mtdinfo->read = slram_read;
206	(*curmtd)->mtdinfo->write = slram_write;
207	(*curmtd)->mtdinfo->owner = THIS_MODULE;
208	(*curmtd)->mtdinfo->type = MTD_RAM;
209	(*curmtd)->mtdinfo->erasesize = SLRAM_BLK_SZ;
210	(*curmtd)->mtdinfo->writesize = 1;
211
212	if (mtd_device_register((*curmtd)->mtdinfo, NULL, 0))	{
213		E("slram: Failed to register new device\n");
214		iounmap(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start);
215		kfree((*curmtd)->mtdinfo->priv);
216		kfree((*curmtd)->mtdinfo);
217		return(-EAGAIN);
218	}
219	T("slram: Registered device %s from %luKiB to %luKiB\n", name,
220			(start / 1024), ((start + length) / 1024));
221	T("slram: Mapped from 0x%p to 0x%p\n",
222			((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start,
223			((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end);
224	return(0);
225}
226
227static void unregister_devices(void)
228{
229	slram_mtd_list_t *nextitem;
230
231	while (slram_mtdlist) {
232		nextitem = slram_mtdlist->next;
233		mtd_device_unregister(slram_mtdlist->mtdinfo);
234		iounmap(((slram_priv_t *)slram_mtdlist->mtdinfo->priv)->start);
235		kfree(slram_mtdlist->mtdinfo->priv);
236		kfree(slram_mtdlist->mtdinfo);
237		kfree(slram_mtdlist);
238		slram_mtdlist = nextitem;
239	}
240}
241
242static unsigned long handle_unit(unsigned long value, char *unit)
243{
244	if ((*unit == 'M') || (*unit == 'm')) {
245		return(value * 1024 * 1024);
246	} else if ((*unit == 'K') || (*unit == 'k')) {
247		return(value * 1024);
248	}
249	return(value);
250}
251
252static int parse_cmdline(char *devname, char *szstart, char *szlength)
253{
254	char *buffer;
255	unsigned long devstart;
256	unsigned long devlength;
257
258	if ((!devname) || (!szstart) || (!szlength)) {
259		unregister_devices();
260		return(-EINVAL);
261	}
262
263	devstart = simple_strtoul(szstart, &buffer, 0);
264	devstart = handle_unit(devstart, buffer);
265
266	if (*(szlength) != '+') {
267		devlength = simple_strtoul(szlength, &buffer, 0);
268		devlength = handle_unit(devlength, buffer) - devstart;
269		if (devlength < devstart)
270			goto err_out;
271
272		devlength -= devstart;
273	} else {
274		devlength = simple_strtoul(szlength + 1, &buffer, 0);
275		devlength = handle_unit(devlength, buffer);
276	}
277	T("slram: devname=%s, devstart=0x%lx, devlength=0x%lx\n",
278			devname, devstart, devlength);
279	if (devlength % SLRAM_BLK_SZ != 0)
280		goto err_out;
281
282	if ((devstart = register_device(devname, devstart, devlength))){
283		unregister_devices();
284		return((int)devstart);
285	}
286	return(0);
287
288err_out:
289	E("slram: Illegal length parameter.\n");
290	return(-EINVAL);
291}
292
293#ifndef MODULE
294
295static int __init mtd_slram_setup(char *str)
296{
297	map = str;
298	return(1);
299}
300
301__setup("slram=", mtd_slram_setup);
302
303#endif
304
305static int __init init_slram(void)
306{
307	char *devname;
308	int i;
309
310#ifndef MODULE
311	char *devstart;
312	char *devlength;
313
314	i = 0;
315
316	if (!map) {
317		E("slram: not enough parameters.\n");
318		return(-EINVAL);
319	}
320	while (map) {
321		devname = devstart = devlength = NULL;
322
323		if (!(devname = strsep(&map, ","))) {
324			E("slram: No devicename specified.\n");
325			break;
326		}
327		T("slram: devname = %s\n", devname);
328		if ((!map) || (!(devstart = strsep(&map, ",")))) {
329			E("slram: No devicestart specified.\n");
330		}
331		T("slram: devstart = %s\n", devstart);
332		if ((!map) || (!(devlength = strsep(&map, ",")))) {
333			E("slram: No devicelength / -end specified.\n");
334		}
335		T("slram: devlength = %s\n", devlength);
336		if (parse_cmdline(devname, devstart, devlength) != 0) {
337			return(-EINVAL);
338		}
339	}
340#else
341	int count;
342
343	for (count = 0; count < SLRAM_MAX_DEVICES_PARAMS && map[count];
344			count++) {
345	}
346
347	if ((count % 3 != 0) || (count == 0)) {
348		E("slram: not enough parameters.\n");
349		return(-EINVAL);
350	}
351	for (i = 0; i < (count / 3); i++) {
352		devname = map[i * 3];
353
354		if (parse_cmdline(devname, map[i * 3 + 1], map[i * 3 + 2])!=0) {
355			return(-EINVAL);
356		}
357
358	}
359#endif /* !MODULE */
360
361	return(0);
362}
363
364static void __exit cleanup_slram(void)
365{
366	unregister_devices();
367}
368
369module_init(init_slram);
370module_exit(cleanup_slram);
371
372MODULE_LICENSE("GPL");
373MODULE_AUTHOR("Jochen Schaeuble <psionic@psionic.de>");
374MODULE_DESCRIPTION("MTD driver for uncached system RAM");
375