Linux Kernel  3.7.1
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slram.c
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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 <[email protected]>
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 
54 typedef struct slram_priv {
57 } slram_priv_t;
58 
59 typedef struct slram_mtd_list {
60  struct mtd_info *mtdinfo;
63 
64 #ifdef MODULE
65 static char *map[SLRAM_MAX_DEVICES_PARAMS];
66 
67 module_param_array(map, charp, NULL, 0);
68 MODULE_PARM_DESC(map, "List of memory regions to map. \"map=<name>, <start>, <length / end>\"");
69 #else
70 static char *map;
71 #endif
72 
73 static slram_mtd_list_t *slram_mtdlist = NULL;
74 
75 static int slram_erase(struct mtd_info *, struct erase_info *);
76 static int slram_point(struct mtd_info *, loff_t, size_t, size_t *, void **,
77  resource_size_t *);
78 static int slram_unpoint(struct mtd_info *, loff_t, size_t);
79 static int slram_read(struct mtd_info *, loff_t, size_t, size_t *, u_char *);
80 static int slram_write(struct mtd_info *, loff_t, size_t, size_t *, const u_char *);
81 
82 static 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 
96 static 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 
106 static int slram_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
107 {
108  return 0;
109 }
110 
111 static 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 
121 static 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 
133 static 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 
202 static 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 
217 static 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 
227 static 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 
263 err_out:
264  E("slram: Illegal length parameter.\n");
265  return(-EINVAL);
266 }
267 
268 #ifndef MODULE
269 
270 static 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 
280 static int __init init_slram(void)
281 {
282  char *devname;
283  int i;
284 
285 #ifndef MODULE
286  char *devstart;
287  char *devlength;
288 
289  i = 0;
290 
291  if (!map) {
292  E("slram: not enough parameters.\n");
293  return(-EINVAL);
294  }
295  while (map) {
296  devname = devstart = devlength = NULL;
297 
298  if (!(devname = strsep(&map, ","))) {
299  E("slram: No devicename specified.\n");
300  break;
301  }
302  T("slram: devname = %s\n", devname);
303  if ((!map) || (!(devstart = strsep(&map, ",")))) {
304  E("slram: No devicestart specified.\n");
305  }
306  T("slram: devstart = %s\n", devstart);
307  if ((!map) || (!(devlength = strsep(&map, ",")))) {
308  E("slram: No devicelength / -end specified.\n");
309  }
310  T("slram: devlength = %s\n", devlength);
311  if (parse_cmdline(devname, devstart, devlength) != 0) {
312  return(-EINVAL);
313  }
314  }
315 #else
316  int count;
317 
318  for (count = 0; count < SLRAM_MAX_DEVICES_PARAMS && map[count];
319  count++) {
320  }
321 
322  if ((count % 3 != 0) || (count == 0)) {
323  E("slram: not enough parameters.\n");
324  return(-EINVAL);
325  }
326  for (i = 0; i < (count / 3); i++) {
327  devname = map[i * 3];
328 
329  if (parse_cmdline(devname, map[i * 3 + 1], map[i * 3 + 2])!=0) {
330  return(-EINVAL);
331  }
332 
333  }
334 #endif /* !MODULE */
335 
336  return(0);
337 }
338 
339 static void __exit cleanup_slram(void)
340 {
341  unregister_devices();
342 }
343 
344 module_init(init_slram);
345 module_exit(cleanup_slram);
346 
347 MODULE_LICENSE("GPL");
348 MODULE_AUTHOR("Jochen Schaeuble <[email protected]>");
349 MODULE_DESCRIPTION("MTD driver for uncached system RAM");