drivers/mtd/devices/slram.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*======================================================================
   3
   4   This driver provides a method to access memory not used by the kernel
   5   itself (i.e. if the kernel commandline mem=xxx is used). To actually
   6   use slram at least mtdblock or mtdchar is required (for block or
   7   character device access).
   8
   9   Usage:
  10
  11   if compiled as loadable module:
  12     modprobe slram map=<name>,<start>,<end/offset>
  13   if statically linked into the kernel use the following kernel cmd.line
  14     slram=<name>,<start>,<end/offset>
  15
  16   <name>: name of the device that will be listed in /proc/mtd
  17   <start>: start of the memory region, decimal or hex (0xabcdef)
  18   <end/offset>: end of the memory region. It's possible to use +0x1234
  19                 to specify the offset instead of the absolute address
  20
  21   NOTE:
  22   With slram it's only possible to map a contiguous memory region. Therefore
  23   if there's a device mapped somewhere in the region specified slram will
  24   fail to load (see kernel log if modprobe fails).
  25
  26   -
  27
  28   Jochen Schaeuble <psionic@psionic.de>
  29
  30 ======================================================================*/
  31
  32
  33 #include <linux/module.h>
  34 #include <linux/uaccess.h>
  35 #include <linux/types.h>
  36 #include <linux/kernel.h>
  37 #include <linux/ptrace.h>
  38 #include <linux/slab.h>
  39 #include <linux/string.h>
  40 #include <linux/timer.h>
  41 #include <linux/major.h>
  42 #include <linux/fs.h>
  43 #include <linux/ioctl.h>
  44 #include <linux/init.h>
  45 #include <linux/io.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
  55 typedef struct slram_priv {
  56         u_char *start;
  57         u_char *end;
  58 } slram_priv_t;
  59
  60 typedef struct slram_mtd_list {
  61         struct mtd_info *mtdinfo;
  62         struct slram_mtd_list *next;
  63 } slram_mtd_list_t;
  64
  65 #ifdef MODULE
  66 static char *map[SLRAM_MAX_DEVICES_PARAMS];
  67
  68 module_param_array(map, charp, NULL, 0);
  69 MODULE_PARM_DESC(map, "List of memory regions to map. \"map=<name>, <start>, <length / end>\"");
  70 #else
  71 static char *map;
  72 #endif
  73
  74 static slram_mtd_list_t *slram_mtdlist = NULL;
  75
  76 static int slram_erase(struct mtd_info *, struct erase_info *);
  77 static int slram_point(struct mtd_info *, loff_t, size_t, size_t *, void **,
  78                 resource_size_t *);
  79 static int slram_unpoint(struct mtd_info *, loff_t, size_t);
  80 static int slram_read(struct mtd_info *, loff_t, size_t, size_t *, u_char *);
  81 static int slram_write(struct mtd_info *, loff_t, size_t, size_t *, const u_char *);
  82
  83 static 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
  89         return(0);
  90 }
  91
  92 static int slram_point(struct mtd_info *mtd, loff_t from, size_t len,
  93                 size_t *retlen, void **virt, resource_size_t *phys)
  94 {
  95         slram_priv_t *priv = mtd->priv;
  96
  97         *virt = priv->start + from;
  98         *retlen = len;
  99         return(0);
 100 }
 101
 102 static int slram_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
 103 {
 104         return 0;
 105 }
 106
 107 static int slram_read(struct mtd_info *mtd, loff_t from, size_t len,
 108                 size_t *retlen, u_char *buf)
 109 {
 110         slram_priv_t *priv = mtd->priv;
 111
 112         memcpy(buf, priv->start + from, len);
 113         *retlen = len;
 114         return(0);
 115 }
 116
 117 static int slram_write(struct mtd_info *mtd, loff_t to, size_t len,
 118                 size_t *retlen, const u_char *buf)
 119 {
 120         slram_priv_t *priv = mtd->priv;
 121
 122         memcpy(priv->start + to, buf, len);
 123         *retlen = len;
 124         return(0);
 125 }
 126
 127 /*====================================================================*/
 128
 129 static int register_device(char *name, unsigned long start, unsigned long length)
 130 {
 131         slram_mtd_list_t **curmtd;
 132
 133         curmtd = &slram_mtdlist;
 134         while (*curmtd) {
 135                 curmtd = &(*curmtd)->next;
 136         }
 137
 138         *curmtd = kmalloc(sizeof(slram_mtd_list_t), GFP_KERNEL);
 139         if (!(*curmtd)) {
 140                 E("slram: Cannot allocate new MTD device.\n");
 141                 return(-ENOMEM);
 142         }
 143         (*curmtd)->mtdinfo = kzalloc(sizeof(struct mtd_info), GFP_KERNEL);
 144         (*curmtd)->next = NULL;
 145
 146         if ((*curmtd)->mtdinfo) {
 147                 (*curmtd)->mtdinfo->priv =
 148                         kzalloc(sizeof(slram_priv_t), GFP_KERNEL);
 149
 150                 if (!(*curmtd)->mtdinfo->priv) {
 151                         kfree((*curmtd)->mtdinfo);
 152                         (*curmtd)->mtdinfo = NULL;
 153                 }
 154         }
 155
 156         if (!(*curmtd)->mtdinfo) {
 157                 E("slram: Cannot allocate new MTD device.\n");
 158                 return(-ENOMEM);
 159         }
 160
 161         if (!(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start =
 162                 memremap(start, length,
 163                          MEMREMAP_WB | MEMREMAP_WT | MEMREMAP_WC))) {
 164                 E("slram: memremap failed\n");
 165                 return -EIO;
 166         }
 167         ((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end =
 168                 ((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start + length;
 169
 170
 171         (*curmtd)->mtdinfo->name = name;
 172         (*curmtd)->mtdinfo->size = length;
 173         (*curmtd)->mtdinfo->flags = MTD_CAP_RAM;
 174         (*curmtd)->mtdinfo->_erase = slram_erase;
 175         (*curmtd)->mtdinfo->_point = slram_point;
 176         (*curmtd)->mtdinfo->_unpoint = slram_unpoint;
 177         (*curmtd)->mtdinfo->_read = slram_read;
 178         (*curmtd)->mtdinfo->_write = slram_write;
 179         (*curmtd)->mtdinfo->owner = THIS_MODULE;
 180         (*curmtd)->mtdinfo->type = MTD_RAM;
 181         (*curmtd)->mtdinfo->erasesize = SLRAM_BLK_SZ;
 182         (*curmtd)->mtdinfo->writesize = 1;
 183
 184         if (mtd_device_register((*curmtd)->mtdinfo, NULL, 0))   {
 185                 E("slram: Failed to register new device\n");
 186                 memunmap(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start);
 187                 kfree((*curmtd)->mtdinfo->priv);
 188                 kfree((*curmtd)->mtdinfo);
 189                 return(-EAGAIN);
 190         }
 191         T("slram: Registered device %s from %luKiB to %luKiB\n", name,
 192                         (start / 1024), ((start + length) / 1024));
 193         T("slram: Mapped from 0x%p to 0x%p\n",
 194                         ((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start,
 195                         ((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end);
 196         return(0);
 197 }
 198
 199 static void unregister_devices(void)
 200 {
 201         slram_mtd_list_t *nextitem;
 202
 203         while (slram_mtdlist) {
 204                 nextitem = slram_mtdlist->next;
 205                 mtd_device_unregister(slram_mtdlist->mtdinfo);
 206                 memunmap(((slram_priv_t *)slram_mtdlist->mtdinfo->priv)->start);
 207                 kfree(slram_mtdlist->mtdinfo->priv);
 208                 kfree(slram_mtdlist->mtdinfo);
 209                 kfree(slram_mtdlist);
 210                 slram_mtdlist = nextitem;
 211         }
 212 }
 213
 214 static unsigned long handle_unit(unsigned long value, char *unit)
 215 {
 216         if ((*unit == 'M') || (*unit == 'm')) {
 217                 return(value * 1024 * 1024);
 218         } else if ((*unit == 'K') || (*unit == 'k')) {
 219                 return(value * 1024);
 220         }
 221         return(value);
 222 }
 223
 224 static int parse_cmdline(char *devname, char *szstart, char *szlength)
 225 {
 226         char *buffer;
 227         unsigned long devstart;
 228         unsigned long devlength;
 229
 230         if ((!devname) || (!szstart) || (!szlength)) {
 231                 unregister_devices();
 232                 return(-EINVAL);
 233         }
 234
 235         devstart = simple_strtoul(szstart, &buffer, 0);
 236         devstart = handle_unit(devstart, buffer);
 237
 238         if (*(szlength) != '+') {
 239                 devlength = simple_strtoul(szlength, &buffer, 0);
 240                 devlength = handle_unit(devlength, buffer);
 241                 if (devlength < devstart)
 242                         goto err_out;
 243
 244                 devlength -= devstart;
 245         } else {
 246                 devlength = simple_strtoul(szlength + 1, &buffer, 0);
 247                 devlength = handle_unit(devlength, buffer);
 248         }
 249         T("slram: devname=%s, devstart=0x%lx, devlength=0x%lx\n",
 250                         devname, devstart, devlength);
 251         if (devlength % SLRAM_BLK_SZ != 0)
 252                 goto err_out;
 253
 254         if ((devstart = register_device(devname, devstart, devlength))){
 255                 unregister_devices();
 256                 return((int)devstart);
 257         }
 258         return(0);
 259
 260 err_out:
 261         E("slram: Illegal length parameter.\n");
 262         return(-EINVAL);
 263 }
 264
 265 #ifndef MODULE
 266
 267 static int __init mtd_slram_setup(char *str)
 268 {
 269         map = str;
 270         return(1);
 271 }
 272
 273 __setup("slram=", mtd_slram_setup);
 274
 275 #endif
 276
 277 static int __init init_slram(void)
 278 {
 279         char *devname;
 280
 281 #ifndef MODULE
 282         char *devstart;
 283         char *devlength;
 284
 285         if (!map) {
 286                 E("slram: not enough parameters.\n");
 287                 return(-EINVAL);
 288         }
 289         while (map) {
 290                 devname = devstart = devlength = NULL;
 291
 292                 if (!(devname = strsep(&map, ","))) {
 293                         E("slram: No devicename specified.\n");
 294                         break;
 295                 }
 296                 T("slram: devname = %s\n", devname);
 297                 if ((!map) || (!(devstart = strsep(&map, ",")))) {
 298                         E("slram: No devicestart specified.\n");
 299                 }
 300                 T("slram: devstart = %s\n", devstart);
 301                 if ((!map) || (!(devlength = strsep(&map, ",")))) {
 302                         E("slram: No devicelength / -end specified.\n");
 303                 }
 304                 T("slram: devlength = %s\n", devlength);
 305                 if (parse_cmdline(devname, devstart, devlength) != 0) {
 306                         return(-EINVAL);
 307                 }
 308         }
 309 #else
 310         int count;
 311         int i;
 312
 313         for (count = 0; count < SLRAM_MAX_DEVICES_PARAMS && map[count];
 314                         count++) {
 315         }
 316
 317         if ((count % 3 != 0) || (count == 0)) {
 318                 E("slram: not enough parameters.\n");
 319                 return(-EINVAL);
 320         }
 321         for (i = 0; i < (count / 3); i++) {
 322                 devname = map[i * 3];
 323
 324                 if (parse_cmdline(devname, map[i * 3 + 1], map[i * 3 + 2])!=0) {
 325                         return(-EINVAL);
 326                 }
 327
 328         }
 329 #endif /* !MODULE */
 330
 331         return(0);
 332 }
 333
 334 static void __exit cleanup_slram(void)
 335 {
 336         unregister_devices();
 337 }
 338
 339 module_init(init_slram);
 340 module_exit(cleanup_slram);
 341
 342 MODULE_LICENSE("GPL");
 343 MODULE_AUTHOR("Jochen Schaeuble <psionic@psionic.de>");
 344 MODULE_DESCRIPTION("MTD driver for uncached system RAM");