mtd/devices/slram.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*======================================================================
0003
0004   This driver provides a method to access memory not used by the kernel
0005   itself (i.e. if the kernel commandline mem=xxx is used). To actually
0006   use slram at least mtdblock or mtdchar is required (for block or
0007   character device access).
0008
0009   Usage:
0010
0011   if compiled as loadable module:
0012     modprobe slram map=<name>,<start>,<end/offset>
0013   if statically linked into the kernel use the following kernel cmd.line
0014     slram=<name>,<start>,<end/offset>
0015
0016   <name>: name of the device that will be listed in /proc/mtd
0017   <start>: start of the memory region, decimal or hex (0xabcdef)
0018   <end/offset>: end of the memory region. It's possible to use +0x1234
0019                 to specify the offset instead of the absolute address
0020
0021   NOTE:
0022   With slram it's only possible to map a contiguous memory region. Therefore
0023   if there's a device mapped somewhere in the region specified slram will
0024   fail to load (see kernel log if modprobe fails).
0025
0026   -
0027
0028   Jochen Schaeuble <psionic@psionic.de>
0029
0030 ======================================================================*/
0031
0032
0033 #include <linux/module.h>
0034 #include <linux/uaccess.h>
0035 #include <linux/types.h>
0036 #include <linux/kernel.h>
0037 #include <linux/ptrace.h>
0038 #include <linux/slab.h>
0039 #include <linux/string.h>
0040 #include <linux/timer.h>
0041 #include <linux/major.h>
0042 #include <linux/fs.h>
0043 #include <linux/ioctl.h>
0044 #include <linux/init.h>
0045 #include <linux/io.h>
0046
0047 #include <linux/mtd/mtd.h>
0048
0049 #define SLRAM_MAX_DEVICES_PARAMS 6      /* 3 parameters / device */
0050 #define SLRAM_BLK_SZ 0x4000
0051
0052 #define T(fmt, args...) printk(KERN_DEBUG fmt, ## args)
0053 #define E(fmt, args...) printk(KERN_NOTICE fmt, ## args)
0054
0055 typedef struct slram_priv {
0056     u_char *start;
0057     u_char *end;
0058 } slram_priv_t;
0059
0060 typedef struct slram_mtd_list {
0061     struct mtd_info *mtdinfo;
0062     struct slram_mtd_list *next;
0063 } slram_mtd_list_t;
0064
0065 #ifdef MODULE
0066 static char *map[SLRAM_MAX_DEVICES_PARAMS];
0067
0068 module_param_array(map, charp, NULL, 0);
0069 MODULE_PARM_DESC(map, "List of memory regions to map. \"map=<name>, <start>, <length / end>\"");
0070 #else
0071 static char *map;
0072 #endif
0073
0074 static slram_mtd_list_t *slram_mtdlist = NULL;
0075
0076 static int slram_erase(struct mtd_info *, struct erase_info *);
0077 static int slram_point(struct mtd_info *, loff_t, size_t, size_t *, void **,
0078         resource_size_t *);
0079 static int slram_unpoint(struct mtd_info *, loff_t, size_t);
0080 static int slram_read(struct mtd_info *, loff_t, size_t, size_t *, u_char *);
0081 static int slram_write(struct mtd_info *, loff_t, size_t, size_t *, const u_char *);
0082
0083 static int slram_erase(struct mtd_info *mtd, struct erase_info *instr)
0084 {
0085     slram_priv_t *priv = mtd->priv;
0086
0087     memset(priv->start + instr->addr, 0xff, instr->len);
0088
0089     return(0);
0090 }
0091
0092 static int slram_point(struct mtd_info *mtd, loff_t from, size_t len,
0093         size_t *retlen, void **virt, resource_size_t *phys)
0094 {
0095     slram_priv_t *priv = mtd->priv;
0096
0097     *virt = priv->start + from;
0098     *retlen = len;
0099     return(0);
0100 }
0101
0102 static int slram_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
0103 {
0104     return 0;
0105 }
0106
0107 static int slram_read(struct mtd_info *mtd, loff_t from, size_t len,
0108         size_t *retlen, u_char *buf)
0109 {
0110     slram_priv_t *priv = mtd->priv;
0111
0112     memcpy(buf, priv->start + from, len);
0113     *retlen = len;
0114     return(0);
0115 }
0116
0117 static int slram_write(struct mtd_info *mtd, loff_t to, size_t len,
0118         size_t *retlen, const u_char *buf)
0119 {
0120     slram_priv_t *priv = mtd->priv;
0121
0122     memcpy(priv->start + to, buf, len);
0123     *retlen = len;
0124     return(0);
0125 }
0126
0127 /*====================================================================*/
0128
0129 static int register_device(char *name, unsigned long start, unsigned long length)
0130 {
0131     slram_mtd_list_t **curmtd;
0132
0133     curmtd = &slram_mtdlist;
0134     while (*curmtd) {
0135         curmtd = &(*curmtd)->next;
0136     }
0137
0138     *curmtd = kmalloc(sizeof(slram_mtd_list_t), GFP_KERNEL);
0139     if (!(*curmtd)) {
0140         E("slram: Cannot allocate new MTD device.\n");
0141         return(-ENOMEM);
0142     }
0143     (*curmtd)->mtdinfo = kzalloc(sizeof(struct mtd_info), GFP_KERNEL);
0144     (*curmtd)->next = NULL;
0145
0146     if ((*curmtd)->mtdinfo) {
0147         (*curmtd)->mtdinfo->priv =
0148             kzalloc(sizeof(slram_priv_t), GFP_KERNEL);
0149
0150         if (!(*curmtd)->mtdinfo->priv) {
0151             kfree((*curmtd)->mtdinfo);
0152             (*curmtd)->mtdinfo = NULL;
0153         }
0154     }
0155
0156     if (!(*curmtd)->mtdinfo) {
0157         E("slram: Cannot allocate new MTD device.\n");
0158         return(-ENOMEM);
0159     }
0160
0161     if (!(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start =
0162         memremap(start, length,
0163              MEMREMAP_WB | MEMREMAP_WT | MEMREMAP_WC))) {
0164         E("slram: memremap failed\n");
0165         return -EIO;
0166     }
0167     ((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end =
0168         ((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start + length;
0169
0170
0171     (*curmtd)->mtdinfo->name = name;
0172     (*curmtd)->mtdinfo->size = length;
0173     (*curmtd)->mtdinfo->flags = MTD_CAP_RAM;
0174     (*curmtd)->mtdinfo->_erase = slram_erase;
0175     (*curmtd)->mtdinfo->_point = slram_point;
0176     (*curmtd)->mtdinfo->_unpoint = slram_unpoint;
0177     (*curmtd)->mtdinfo->_read = slram_read;
0178     (*curmtd)->mtdinfo->_write = slram_write;
0179     (*curmtd)->mtdinfo->owner = THIS_MODULE;
0180     (*curmtd)->mtdinfo->type = MTD_RAM;
0181     (*curmtd)->mtdinfo->erasesize = SLRAM_BLK_SZ;
0182     (*curmtd)->mtdinfo->writesize = 1;
0183
0184     if (mtd_device_register((*curmtd)->mtdinfo, NULL, 0))   {
0185         E("slram: Failed to register new device\n");
0186         memunmap(((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start);
0187         kfree((*curmtd)->mtdinfo->priv);
0188         kfree((*curmtd)->mtdinfo);
0189         return(-EAGAIN);
0190     }
0191     T("slram: Registered device %s from %luKiB to %luKiB\n", name,
0192             (start / 1024), ((start + length) / 1024));
0193     T("slram: Mapped from 0x%p to 0x%p\n",
0194             ((slram_priv_t *)(*curmtd)->mtdinfo->priv)->start,
0195             ((slram_priv_t *)(*curmtd)->mtdinfo->priv)->end);
0196     return(0);
0197 }
0198
0199 static void unregister_devices(void)
0200 {
0201     slram_mtd_list_t *nextitem;
0202
0203     while (slram_mtdlist) {
0204         nextitem = slram_mtdlist->next;
0205         mtd_device_unregister(slram_mtdlist->mtdinfo);
0206         memunmap(((slram_priv_t *)slram_mtdlist->mtdinfo->priv)->start);
0207         kfree(slram_mtdlist->mtdinfo->priv);
0208         kfree(slram_mtdlist->mtdinfo);
0209         kfree(slram_mtdlist);
0210         slram_mtdlist = nextitem;
0211     }
0212 }
0213
0214 static unsigned long handle_unit(unsigned long value, char *unit)
0215 {
0216     if ((*unit == 'M') || (*unit == 'm')) {
0217         return(value * 1024 * 1024);
0218     } else if ((*unit == 'K') || (*unit == 'k')) {
0219         return(value * 1024);
0220     }
0221     return(value);
0222 }
0223
0224 static int parse_cmdline(char *devname, char *szstart, char *szlength)
0225 {
0226     char *buffer;
0227     unsigned long devstart;
0228     unsigned long devlength;
0229
0230     if ((!devname) || (!szstart) || (!szlength)) {
0231         unregister_devices();
0232         return(-EINVAL);
0233     }
0234
0235     devstart = simple_strtoul(szstart, &buffer, 0);
0236     devstart = handle_unit(devstart, buffer);
0237
0238     if (*(szlength) != '+') {
0239         devlength = simple_strtoul(szlength, &buffer, 0);
0240         devlength = handle_unit(devlength, buffer);
0241         if (devlength < devstart)
0242             goto err_out;
0243
0244         devlength -= devstart;
0245     } else {
0246         devlength = simple_strtoul(szlength + 1, &buffer, 0);
0247         devlength = handle_unit(devlength, buffer);
0248     }
0249     T("slram: devname=%s, devstart=0x%lx, devlength=0x%lx\n",
0250             devname, devstart, devlength);
0251     if (devlength % SLRAM_BLK_SZ != 0)
0252         goto err_out;
0253
0254     if ((devstart = register_device(devname, devstart, devlength))){
0255         unregister_devices();
0256         return((int)devstart);
0257     }
0258     return(0);
0259
0260 err_out:
0261     E("slram: Illegal length parameter.\n");
0262     return(-EINVAL);
0263 }
0264
0265 #ifndef MODULE
0266
0267 static int __init mtd_slram_setup(char *str)
0268 {
0269     map = str;
0270     return(1);
0271 }
0272
0273 __setup("slram=", mtd_slram_setup);
0274
0275 #endif
0276
0277 static int __init init_slram(void)
0278 {
0279     char *devname;
0280
0281 #ifndef MODULE
0282     char *devstart;
0283     char *devlength;
0284
0285     if (!map) {
0286         E("slram: not enough parameters.\n");
0287         return(-EINVAL);
0288     }
0289     while (map) {
0290         devname = devstart = devlength = NULL;
0291
0292         if (!(devname = strsep(&map, ","))) {
0293             E("slram: No devicename specified.\n");
0294             break;
0295         }
0296         T("slram: devname = %s\n", devname);
0297         if ((!map) || (!(devstart = strsep(&map, ",")))) {
0298             E("slram: No devicestart specified.\n");
0299         }
0300         T("slram: devstart = %s\n", devstart);
0301         if ((!map) || (!(devlength = strsep(&map, ",")))) {
0302             E("slram: No devicelength / -end specified.\n");
0303         }
0304         T("slram: devlength = %s\n", devlength);
0305         if (parse_cmdline(devname, devstart, devlength) != 0) {
0306             return(-EINVAL);
0307         }
0308     }
0309 #else
0310     int count;
0311     int i;
0312
0313     for (count = 0; count < SLRAM_MAX_DEVICES_PARAMS && map[count];
0314             count++) {
0315     }
0316
0317     if ((count % 3 != 0) || (count == 0)) {
0318         E("slram: not enough parameters.\n");
0319         return(-EINVAL);
0320     }
0321     for (i = 0; i < (count / 3); i++) {
0322         devname = map[i * 3];
0323
0324         if (parse_cmdline(devname, map[i * 3 + 1], map[i * 3 + 2])!=0) {
0325             return(-EINVAL);
0326         }
0327
0328     }
0329 #endif /* !MODULE */
0330
0331     return(0);
0332 }
0333
0334 static void __exit cleanup_slram(void)
0335 {
0336     unregister_devices();
0337 }
0338
0339 module_init(init_slram);
0340 module_exit(cleanup_slram);
0341
0342 MODULE_LICENSE("GPL");
0343 MODULE_AUTHOR("Jochen Schaeuble <psionic@psionic.de>");
0344 MODULE_DESCRIPTION("MTD driver for uncached system RAM");