slram.c revision 0dd5235f51fb0eb0b8cef3fed35be39b8a06d7bd 
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	memset(priv->start + instr->addr, 0xff, instr->len);
88	/* This'll catch a few races. Free the thing before returning :)
89	 * I don't feel at all ashamed. This kind of thing is possible anyway
90	 * with flash, but unlikely.
91	 */
92	instr->state = MTD_ERASE_DONE;
93	mtd_erase_callback(instr);
94	return(0);
95}
96
97static int slram_point(struct mtd_info *mtd, loff_t from, size_t len,
98		size_t *retlen, void **virt, resource_size_t *phys)
99{
100	slram_priv_t *priv = mtd->priv;
101
102	*virt = priv->start + from;
103	*retlen = len;
104	return(0);
105}
106
107static int slram_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
108{
109	return 0;
110}
111
112static int slram_read(struct mtd_info *mtd, loff_t from, size_t len,
113		size_t *retlen, u_char *buf)
114{
115	slram_priv_t *priv = mtd->priv;
116
117	memcpy(buf, priv->start + from, len);
118	*retlen = len;
119	return(0);
120}
121
122static int slram_write(struct mtd_info *mtd, loff_t to, size_t len,
123		size_t *retlen, const u_char *buf)
124{
125	slram_priv_t *priv = mtd->priv;
126
127	memcpy(priv->start + to, buf, len);
128	*retlen = len;
129	return(0);
130}
131
132/*====================================================================*/
133
134static int register_device(char *name, unsigned long start, unsigned long length)
135{
136	slram_mtd_list_t **curmtd;
137
138	curmtd = &slram_mtdlist;
139	while (*curmtd) {
140		curmtd = &(*curmtd)->next;
141	}
142
143	*curmtd = kmalloc(sizeof(slram_mtd_list_t), GFP_KERNEL);
144	if (!(*curmtd)) {
145		E("slram: Cannot allocate new MTD device.\n");
146		return(-ENOMEM);
147	}
148	(*curmtd)->mtdinfo = kzalloc(sizeof(struct mtd_info), GFP_KERNEL);
149	(*curmtd)->next = NULL;
150
151	if ((*curmtd)->mtdinfo)	{
152		(*curmtd)->mtdinfo->priv =
153			kzalloc(sizeof(slram_priv_t), GFP_KERNEL);
154
155		if (!(*curmtd)->mtdinfo->priv) {
156			kfree((*curmtd)->mtdinfo);
157			(*curmtd)->mtdinfo = NULL;
158		}
159	}
160
161	if (!(*curmtd)->mtdinfo) {
162		E("slram: Cannot allocate new MTD device.\n");
163		return(-ENOMEM);
164	}
165
166	if (!(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start =
167				ioremap(start, length))) {
168		E("slram: ioremap failed\n");
169		return -EIO;
170	}
171	((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end =
172		((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start + length;
173
174
175	(*curmtd)->mtdinfo->name = name;
176	(*curmtd)->mtdinfo->size = length;
177	(*curmtd)->mtdinfo->flags = MTD_CAP_RAM;
178	(*curmtd)->mtdinfo->_erase = slram_erase;
179	(*curmtd)->mtdinfo->_point = slram_point;
180	(*curmtd)->mtdinfo->_unpoint = slram_unpoint;
181	(*curmtd)->mtdinfo->_read = slram_read;
182	(*curmtd)->mtdinfo->_write = slram_write;
183	(*curmtd)->mtdinfo->owner = THIS_MODULE;
184	(*curmtd)->mtdinfo->type = MTD_RAM;
185	(*curmtd)->mtdinfo->erasesize = SLRAM_BLK_SZ;
186	(*curmtd)->mtdinfo->writesize = 1;
187
188	if (mtd_device_register((*curmtd)->mtdinfo, NULL, 0))	{
189		E("slram: Failed to register new device\n");
190		iounmap(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start);
191		kfree((*curmtd)->mtdinfo->priv);
192		kfree((*curmtd)->mtdinfo);
193		return(-EAGAIN);
194	}
195	T("slram: Registered device %s from %luKiB to %luKiB\n", name,
196			(start / 1024), ((start + length) / 1024));
197	T("slram: Mapped from 0x%p to 0x%p\n",
198			((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start,
199			((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end);
200	return(0);
201}
202
203static void unregister_devices(void)
204{
205	slram_mtd_list_t *nextitem;
206
207	while (slram_mtdlist) {
208		nextitem = slram_mtdlist->next;
209		mtd_device_unregister(slram_mtdlist->mtdinfo);
210		iounmap(((slram_priv_t *)slram_mtdlist->mtdinfo->priv)->start);
211		kfree(slram_mtdlist->mtdinfo->priv);
212		kfree(slram_mtdlist->mtdinfo);
213		kfree(slram_mtdlist);
214		slram_mtdlist = nextitem;
215	}
216}
217
218static unsigned long handle_unit(unsigned long value, char *unit)
219{
220	if ((*unit == 'M') || (*unit == 'm')) {
221		return(value * 1024 * 1024);
222	} else if ((*unit == 'K') || (*unit == 'k')) {
223		return(value * 1024);
224	}
225	return(value);
226}
227
228static int parse_cmdline(char *devname, char *szstart, char *szlength)
229{
230	char *buffer;
231	unsigned long devstart;
232	unsigned long devlength;
233
234	if ((!devname) || (!szstart) || (!szlength)) {
235		unregister_devices();
236		return(-EINVAL);
237	}
238
239	devstart = simple_strtoul(szstart, &buffer, 0);
240	devstart = handle_unit(devstart, buffer);
241
242	if (*(szlength) != '+') {
243		devlength = simple_strtoul(szlength, &buffer, 0);
244		devlength = handle_unit(devlength, buffer) - devstart;
245		if (devlength < devstart)
246			goto err_out;
247
248		devlength -= devstart;
249	} else {
250		devlength = simple_strtoul(szlength + 1, &buffer, 0);
251		devlength = handle_unit(devlength, buffer);
252	}
253	T("slram: devname=%s, devstart=0x%lx, devlength=0x%lx\n",
254			devname, devstart, devlength);
255	if (devlength % SLRAM_BLK_SZ != 0)
256		goto err_out;
257
258	if ((devstart = register_device(devname, devstart, devlength))){
259		unregister_devices();
260		return((int)devstart);
261	}
262	return(0);
263
264err_out:
265	E("slram: Illegal length parameter.\n");
266	return(-EINVAL);
267}
268
269#ifndef MODULE
270
271static int __init mtd_slram_setup(char *str)
272{
273	map = str;
274	return(1);
275}
276
277__setup("slram=", mtd_slram_setup);
278
279#endif
280
281static int __init init_slram(void)
282{
283	char *devname;
284	int i;
285
286#ifndef MODULE
287	char *devstart;
288	char *devlength;
289
290	i = 0;
291
292	if (!map) {
293		E("slram: not enough parameters.\n");
294		return(-EINVAL);
295	}
296	while (map) {
297		devname = devstart = devlength = NULL;
298
299		if (!(devname = strsep(&map, ","))) {
300			E("slram: No devicename specified.\n");
301			break;
302		}
303		T("slram: devname = %s\n", devname);
304		if ((!map) || (!(devstart = strsep(&map, ",")))) {
305			E("slram: No devicestart specified.\n");
306		}
307		T("slram: devstart = %s\n", devstart);
308		if ((!map) || (!(devlength = strsep(&map, ",")))) {
309			E("slram: No devicelength / -end specified.\n");
310		}
311		T("slram: devlength = %s\n", devlength);
312		if (parse_cmdline(devname, devstart, devlength) != 0) {
313			return(-EINVAL);
314		}
315	}
316#else
317	int count;
318
319	for (count = 0; count < SLRAM_MAX_DEVICES_PARAMS && map[count];
320			count++) {
321	}
322
323	if ((count % 3 != 0) || (count == 0)) {
324		E("slram: not enough parameters.\n");
325		return(-EINVAL);
326	}
327	for (i = 0; i < (count / 3); i++) {
328		devname = map[i * 3];
329
330		if (parse_cmdline(devname, map[i * 3 + 1], map[i * 3 + 2])!=0) {
331			return(-EINVAL);
332		}
333
334	}
335#endif /* !MODULE */
336
337	return(0);
338}
339
340static void __exit cleanup_slram(void)
341{
342	unregister_devices();
343}
344
345module_init(init_slram);
346module_exit(cleanup_slram);
347
348MODULE_LICENSE("GPL");
349MODULE_AUTHOR("Jochen Schaeuble <psionic@psionic.de>");
350MODULE_DESCRIPTION("MTD driver for uncached system RAM");
351