slram.c revision 5e4e6e3fdf48c1b012e2b6e80ed1d7e99d4fa6d1 
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#include <asm/system.h>
46
47#include <linux/mtd/mtd.h>
48
49#define SLRAM_MAX_DEVICES_PARAMS 6		/* 3 parameters / device */
50#define SLRAM_BLK_SZ 0x4000
51
52#define T(fmt, args...) printk(KERN_DEBUG fmt, ## args)
53#define E(fmt, args...) printk(KERN_NOTICE fmt, ## args)
54
55typedef struct slram_priv {
56	u_char *start;
57	u_char *end;
58} slram_priv_t;
59
60typedef struct slram_mtd_list {
61	struct mtd_info *mtdinfo;
62	struct slram_mtd_list *next;
63} slram_mtd_list_t;
64
65#ifdef MODULE
66static char *map[SLRAM_MAX_DEVICES_PARAMS];
67
68module_param_array(map, charp, NULL, 0);
69MODULE_PARM_DESC(map, "List of memory regions to map. \"map=<name>, <start>, <length / end>\"");
70#else
71static char *map;
72#endif
73
74static slram_mtd_list_t *slram_mtdlist = NULL;
75
76static int slram_erase(struct mtd_info *, struct erase_info *);
77static int slram_point(struct mtd_info *, loff_t, size_t, size_t *, void **,
78		resource_size_t *);
79static int slram_unpoint(struct mtd_info *, loff_t, size_t);
80static int slram_read(struct mtd_info *, loff_t, size_t, size_t *, u_char *);
81static int slram_write(struct mtd_info *, loff_t, size_t, size_t *, const u_char *);
82
83static int slram_erase(struct mtd_info *mtd, struct erase_info *instr)
84{
85	slram_priv_t *priv = mtd->priv;
86
87	if (instr->addr + instr->len > mtd->size) {
88		return(-EINVAL);
89	}
90
91	memset(priv->start + instr->addr, 0xff, instr->len);
92
93	/* This'll catch a few races. Free the thing before returning :)
94	 * I don't feel at all ashamed. This kind of thing is possible anyway
95	 * with flash, but unlikely.
96	 */
97
98	instr->state = MTD_ERASE_DONE;
99
100	mtd_erase_callback(instr);
101
102	return(0);
103}
104
105static int slram_point(struct mtd_info *mtd, loff_t from, size_t len,
106		size_t *retlen, void **virt, resource_size_t *phys)
107{
108	slram_priv_t *priv = mtd->priv;
109
110	/* can we return a physical address with this driver? */
111	if (phys)
112		return -EINVAL;
113
114	if (from + len > mtd->size)
115		return -EINVAL;
116
117	*virt = priv->start + from;
118	*retlen = len;
119	return(0);
120}
121
122static int slram_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
123{
124	return 0;
125}
126
127static int slram_read(struct mtd_info *mtd, loff_t from, size_t len,
128		size_t *retlen, u_char *buf)
129{
130	slram_priv_t *priv = mtd->priv;
131
132	if (from > mtd->size)
133		return -EINVAL;
134
135	if (from + len > mtd->size)
136		len = mtd->size - from;
137
138	memcpy(buf, priv->start + from, len);
139
140	*retlen = len;
141	return(0);
142}
143
144static int slram_write(struct mtd_info *mtd, loff_t to, size_t len,
145		size_t *retlen, const u_char *buf)
146{
147	slram_priv_t *priv = mtd->priv;
148
149	if (to + len > mtd->size)
150		return -EINVAL;
151
152	memcpy(priv->start + to, buf, len);
153
154	*retlen = len;
155	return(0);
156}
157
158/*====================================================================*/
159
160static int register_device(char *name, unsigned long start, unsigned long length)
161{
162	slram_mtd_list_t **curmtd;
163
164	curmtd = &slram_mtdlist;
165	while (*curmtd) {
166		curmtd = &(*curmtd)->next;
167	}
168
169	*curmtd = kmalloc(sizeof(slram_mtd_list_t), GFP_KERNEL);
170	if (!(*curmtd)) {
171		E("slram: Cannot allocate new MTD device.\n");
172		return(-ENOMEM);
173	}
174	(*curmtd)->mtdinfo = kzalloc(sizeof(struct mtd_info), GFP_KERNEL);
175	(*curmtd)->next = NULL;
176
177	if ((*curmtd)->mtdinfo)	{
178		(*curmtd)->mtdinfo->priv =
179			kzalloc(sizeof(slram_priv_t), GFP_KERNEL);
180
181		if (!(*curmtd)->mtdinfo->priv) {
182			kfree((*curmtd)->mtdinfo);
183			(*curmtd)->mtdinfo = NULL;
184		}
185	}
186
187	if (!(*curmtd)->mtdinfo) {
188		E("slram: Cannot allocate new MTD device.\n");
189		return(-ENOMEM);
190	}
191
192	if (!(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start =
193				ioremap(start, length))) {
194		E("slram: ioremap failed\n");
195		return -EIO;
196	}
197	((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end =
198		((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start + length;
199
200
201	(*curmtd)->mtdinfo->name = name;
202	(*curmtd)->mtdinfo->size = length;
203	(*curmtd)->mtdinfo->flags = MTD_CAP_RAM;
204	(*curmtd)->mtdinfo->_erase = slram_erase;
205	(*curmtd)->mtdinfo->_point = slram_point;
206	(*curmtd)->mtdinfo->_unpoint = slram_unpoint;
207	(*curmtd)->mtdinfo->_read = slram_read;
208	(*curmtd)->mtdinfo->_write = slram_write;
209	(*curmtd)->mtdinfo->owner = THIS_MODULE;
210	(*curmtd)->mtdinfo->type = MTD_RAM;
211	(*curmtd)->mtdinfo->erasesize = SLRAM_BLK_SZ;
212	(*curmtd)->mtdinfo->writesize = 1;
213
214	if (mtd_device_register((*curmtd)->mtdinfo, NULL, 0))	{
215		E("slram: Failed to register new device\n");
216		iounmap(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start);
217		kfree((*curmtd)->mtdinfo->priv);
218		kfree((*curmtd)->mtdinfo);
219		return(-EAGAIN);
220	}
221	T("slram: Registered device %s from %luKiB to %luKiB\n", name,
222			(start / 1024), ((start + length) / 1024));
223	T("slram: Mapped from 0x%p to 0x%p\n",
224			((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start,
225			((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end);
226	return(0);
227}
228
229static void unregister_devices(void)
230{
231	slram_mtd_list_t *nextitem;
232
233	while (slram_mtdlist) {
234		nextitem = slram_mtdlist->next;
235		mtd_device_unregister(slram_mtdlist->mtdinfo);
236		iounmap(((slram_priv_t *)slram_mtdlist->mtdinfo->priv)->start);
237		kfree(slram_mtdlist->mtdinfo->priv);
238		kfree(slram_mtdlist->mtdinfo);
239		kfree(slram_mtdlist);
240		slram_mtdlist = nextitem;
241	}
242}
243
244static unsigned long handle_unit(unsigned long value, char *unit)
245{
246	if ((*unit == 'M') || (*unit == 'm')) {
247		return(value * 1024 * 1024);
248	} else if ((*unit == 'K') || (*unit == 'k')) {
249		return(value * 1024);
250	}
251	return(value);
252}
253
254static int parse_cmdline(char *devname, char *szstart, char *szlength)
255{
256	char *buffer;
257	unsigned long devstart;
258	unsigned long devlength;
259
260	if ((!devname) || (!szstart) || (!szlength)) {
261		unregister_devices();
262		return(-EINVAL);
263	}
264
265	devstart = simple_strtoul(szstart, &buffer, 0);
266	devstart = handle_unit(devstart, buffer);
267
268	if (*(szlength) != '+') {
269		devlength = simple_strtoul(szlength, &buffer, 0);
270		devlength = handle_unit(devlength, buffer) - devstart;
271		if (devlength < devstart)
272			goto err_out;
273
274		devlength -= devstart;
275	} else {
276		devlength = simple_strtoul(szlength + 1, &buffer, 0);
277		devlength = handle_unit(devlength, buffer);
278	}
279	T("slram: devname=%s, devstart=0x%lx, devlength=0x%lx\n",
280			devname, devstart, devlength);
281	if (devlength % SLRAM_BLK_SZ != 0)
282		goto err_out;
283
284	if ((devstart = register_device(devname, devstart, devlength))){
285		unregister_devices();
286		return((int)devstart);
287	}
288	return(0);
289
290err_out:
291	E("slram: Illegal length parameter.\n");
292	return(-EINVAL);
293}
294
295#ifndef MODULE
296
297static int __init mtd_slram_setup(char *str)
298{
299	map = str;
300	return(1);
301}
302
303__setup("slram=", mtd_slram_setup);
304
305#endif
306
307static int __init init_slram(void)
308{
309	char *devname;
310	int i;
311
312#ifndef MODULE
313	char *devstart;
314	char *devlength;
315
316	i = 0;
317
318	if (!map) {
319		E("slram: not enough parameters.\n");
320		return(-EINVAL);
321	}
322	while (map) {
323		devname = devstart = devlength = NULL;
324
325		if (!(devname = strsep(&map, ","))) {
326			E("slram: No devicename specified.\n");
327			break;
328		}
329		T("slram: devname = %s\n", devname);
330		if ((!map) || (!(devstart = strsep(&map, ",")))) {
331			E("slram: No devicestart specified.\n");
332		}
333		T("slram: devstart = %s\n", devstart);
334		if ((!map) || (!(devlength = strsep(&map, ",")))) {
335			E("slram: No devicelength / -end specified.\n");
336		}
337		T("slram: devlength = %s\n", devlength);
338		if (parse_cmdline(devname, devstart, devlength) != 0) {
339			return(-EINVAL);
340		}
341	}
342#else
343	int count;
344
345	for (count = 0; count < SLRAM_MAX_DEVICES_PARAMS && map[count];
346			count++) {
347	}
348
349	if ((count % 3 != 0) || (count == 0)) {
350		E("slram: not enough parameters.\n");
351		return(-EINVAL);
352	}
353	for (i = 0; i < (count / 3); i++) {
354		devname = map[i * 3];
355
356		if (parse_cmdline(devname, map[i * 3 + 1], map[i * 3 + 2])!=0) {
357			return(-EINVAL);
358		}
359
360	}
361#endif /* !MODULE */
362
363	return(0);
364}
365
366static void __exit cleanup_slram(void)
367{
368	unregister_devices();
369}
370
371module_init(init_slram);
372module_exit(cleanup_slram);
373
374MODULE_LICENSE("GPL");
375MODULE_AUTHOR("Jochen Schaeuble <psionic@psionic.de>");
376MODULE_DESCRIPTION("MTD driver for uncached system RAM");
377