slram.c revision ed491d2063d41a09a35c7db1a99fea88dbfcd7aa 
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 int 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	memset(priv->start + instr->addr, 0xff, instr->len);
87	/* This'll catch a few races. Free the thing before returning :)
88	 * I don't feel at all ashamed. This kind of thing is possible anyway
89	 * with flash, but unlikely.
90	 */
91	instr->state = MTD_ERASE_DONE;
92	mtd_erase_callback(instr);
93	return(0);
94}
95
96static int slram_point(struct mtd_info *mtd, loff_t from, size_t len,
97		size_t *retlen, void **virt, resource_size_t *phys)
98{
99	slram_priv_t *priv = mtd->priv;
100
101	*virt = priv->start + from;
102	*retlen = len;
103	return(0);
104}
105
106static int slram_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
107{
108	return 0;
109}
110
111static int slram_read(struct mtd_info *mtd, loff_t from, size_t len,
112		size_t *retlen, u_char *buf)
113{
114	slram_priv_t *priv = mtd->priv;
115
116	memcpy(buf, priv->start + from, len);
117	*retlen = len;
118	return(0);
119}
120
121static int slram_write(struct mtd_info *mtd, loff_t to, size_t len,
122		size_t *retlen, const u_char *buf)
123{
124	slram_priv_t *priv = mtd->priv;
125
126	memcpy(priv->start + to, buf, len);
127	*retlen = len;
128	return(0);
129}
130
131/*====================================================================*/
132
133static int register_device(char *name, unsigned long start, unsigned long length)
134{
135	slram_mtd_list_t **curmtd;
136
137	curmtd = &slram_mtdlist;
138	while (*curmtd) {
139		curmtd = &(*curmtd)->next;
140	}
141
142	*curmtd = kmalloc(sizeof(slram_mtd_list_t), GFP_KERNEL);
143	if (!(*curmtd)) {
144		E("slram: Cannot allocate new MTD device.\n");
145		return(-ENOMEM);
146	}
147	(*curmtd)->mtdinfo = kzalloc(sizeof(struct mtd_info), GFP_KERNEL);
148	(*curmtd)->next = NULL;
149
150	if ((*curmtd)->mtdinfo)	{
151		(*curmtd)->mtdinfo->priv =
152			kzalloc(sizeof(slram_priv_t), GFP_KERNEL);
153
154		if (!(*curmtd)->mtdinfo->priv) {
155			kfree((*curmtd)->mtdinfo);
156			(*curmtd)->mtdinfo = NULL;
157		}
158	}
159
160	if (!(*curmtd)->mtdinfo) {
161		E("slram: Cannot allocate new MTD device.\n");
162		return(-ENOMEM);
163	}
164
165	if (!(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start =
166				ioremap(start, length))) {
167		E("slram: ioremap failed\n");
168		return -EIO;
169	}
170	((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end =
171		((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start + length;
172
173
174	(*curmtd)->mtdinfo->name = name;
175	(*curmtd)->mtdinfo->size = length;
176	(*curmtd)->mtdinfo->flags = MTD_CAP_RAM;
177	(*curmtd)->mtdinfo->_erase = slram_erase;
178	(*curmtd)->mtdinfo->_point = slram_point;
179	(*curmtd)->mtdinfo->_unpoint = slram_unpoint;
180	(*curmtd)->mtdinfo->_read = slram_read;
181	(*curmtd)->mtdinfo->_write = slram_write;
182	(*curmtd)->mtdinfo->owner = THIS_MODULE;
183	(*curmtd)->mtdinfo->type = MTD_RAM;
184	(*curmtd)->mtdinfo->erasesize = SLRAM_BLK_SZ;
185	(*curmtd)->mtdinfo->writesize = 1;
186
187	if (mtd_device_register((*curmtd)->mtdinfo, NULL, 0))	{
188		E("slram: Failed to register new device\n");
189		iounmap(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start);
190		kfree((*curmtd)->mtdinfo->priv);
191		kfree((*curmtd)->mtdinfo);
192		return(-EAGAIN);
193	}
194	T("slram: Registered device %s from %luKiB to %luKiB\n", name,
195			(start / 1024), ((start + length) / 1024));
196	T("slram: Mapped from 0x%p to 0x%p\n",
197			((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start,
198			((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end);
199	return(0);
200}
201
202static void unregister_devices(void)
203{
204	slram_mtd_list_t *nextitem;
205
206	while (slram_mtdlist) {
207		nextitem = slram_mtdlist->next;
208		mtd_device_unregister(slram_mtdlist->mtdinfo);
209		iounmap(((slram_priv_t *)slram_mtdlist->mtdinfo->priv)->start);
210		kfree(slram_mtdlist->mtdinfo->priv);
211		kfree(slram_mtdlist->mtdinfo);
212		kfree(slram_mtdlist);
213		slram_mtdlist = nextitem;
214	}
215}
216
217static unsigned long handle_unit(unsigned long value, char *unit)
218{
219	if ((*unit == 'M') || (*unit == 'm')) {
220		return(value * 1024 * 1024);
221	} else if ((*unit == 'K') || (*unit == 'k')) {
222		return(value * 1024);
223	}
224	return(value);
225}
226
227static int parse_cmdline(char *devname, char *szstart, char *szlength)
228{
229	char *buffer;
230	unsigned long devstart;
231	unsigned long devlength;
232
233	if ((!devname) || (!szstart) || (!szlength)) {
234		unregister_devices();
235		return(-EINVAL);
236	}
237
238	devstart = simple_strtoul(szstart, &buffer, 0);
239	devstart = handle_unit(devstart, buffer);
240
241	if (*(szlength) != '+') {
242		devlength = simple_strtoul(szlength, &buffer, 0);
243		devlength = handle_unit(devlength, buffer);
244		if (devlength < devstart)
245			goto err_out;
246
247		devlength -= devstart;
248	} else {
249		devlength = simple_strtoul(szlength + 1, &buffer, 0);
250		devlength = handle_unit(devlength, buffer);
251	}
252	T("slram: devname=%s, devstart=0x%lx, devlength=0x%lx\n",
253			devname, devstart, devlength);
254	if (devlength % SLRAM_BLK_SZ != 0)
255		goto err_out;
256
257	if ((devstart = register_device(devname, devstart, devlength))){
258		unregister_devices();
259		return((int)devstart);
260	}
261	return(0);
262
263err_out:
264	E("slram: Illegal length parameter.\n");
265	return(-EINVAL);
266}
267
268#ifndef MODULE
269
270static int __init mtd_slram_setup(char *str)
271{
272	map = str;
273	return(1);
274}
275
276__setup("slram=", mtd_slram_setup);
277
278#endif
279
280static int __init init_slram(void)
281{
282	char *devname;
283
284#ifndef MODULE
285	char *devstart;
286	char *devlength;
287
288	if (!map) {
289		E("slram: not enough parameters.\n");
290		return(-EINVAL);
291	}
292	while (map) {
293		devname = devstart = devlength = NULL;
294
295		if (!(devname = strsep(&map, ","))) {
296			E("slram: No devicename specified.\n");
297			break;
298		}
299		T("slram: devname = %s\n", devname);
300		if ((!map) || (!(devstart = strsep(&map, ",")))) {
301			E("slram: No devicestart specified.\n");
302		}
303		T("slram: devstart = %s\n", devstart);
304		if ((!map) || (!(devlength = strsep(&map, ",")))) {
305			E("slram: No devicelength / -end specified.\n");
306		}
307		T("slram: devlength = %s\n", devlength);
308		if (parse_cmdline(devname, devstart, devlength) != 0) {
309			return(-EINVAL);
310		}
311	}
312#else
313	int count;
314	int i;
315
316	for (count = 0; count < SLRAM_MAX_DEVICES_PARAMS && map[count];
317			count++) {
318	}
319
320	if ((count % 3 != 0) || (count == 0)) {
321		E("slram: not enough parameters.\n");
322		return(-EINVAL);
323	}
324	for (i = 0; i < (count / 3); i++) {
325		devname = map[i * 3];
326
327		if (parse_cmdline(devname, map[i * 3 + 1], map[i * 3 + 2])!=0) {
328			return(-EINVAL);
329		}
330
331	}
332#endif /* !MODULE */
333
334	return(0);
335}
336
337static void __exit cleanup_slram(void)
338{
339	unregister_devices();
340}
341
342module_init(init_slram);
343module_exit(cleanup_slram);
344
345MODULE_LICENSE("GPL");
346MODULE_AUTHOR("Jochen Schaeuble <psionic@psionic.de>");
347MODULE_DESCRIPTION("MTD driver for uncached system RAM");
348