drivers/char/mem.c

   1 /*
   2  *  linux/drivers/char/mem.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  *
   6  *  Added devfs support.
   7  *    Jan-11-1998, C. Scott Ananian <cananian@alumni.princeton.edu>
   8  *  Shared /dev/zero mmaping support, Feb 2000, Kanoj Sarcar <kanoj@sgi.com>
   9  */
  10
  11 #include <linux/config.h>
  12 #include <linux/mm.h>
  13 #include <linux/miscdevice.h>
  14 #include <linux/slab.h>
  15 #include <linux/vmalloc.h>
  16 #include <linux/mman.h>
  17 #include <linux/random.h>
  18 #include <linux/init.h>
  19 #include <linux/raw.h>
  20 #include <linux/tty.h>
  21 #include <linux/capability.h>
  22 #include <linux/smp_lock.h>
  23 #include <linux/devfs_fs_kernel.h>
  24 #include <linux/ptrace.h>
  25 #include <linux/device.h>
  26
  27 #include <asm/uaccess.h>
  28 #include <asm/io.h>
  29
  30 #ifdef CONFIG_IA64
  31 # include <linux/efi.h>
  32 #endif
  33
  34 #if defined(CONFIG_S390_TAPE) && defined(CONFIG_S390_TAPE_CHAR)
  35 extern void tapechar_init(void);
  36 #endif
  37
  38 /*
  39  * Architectures vary in how they handle caching for addresses
  40  * outside of main memory.
  41  *
  42  */
  43 static inline int uncached_access(struct file *file, unsigned long addr)
  44 {
  45 #if defined(__i386__)
  46         /*
  47          * On the PPro and successors, the MTRRs are used to set
  48          * memory types for physical addresses outside main memory,
  49          * so blindly setting PCD or PWT on those pages is wrong.
  50          * For Pentiums and earlier, the surround logic should disable
  51          * caching for the high addresses through the KEN pin, but
  52          * we maintain the tradition of paranoia in this code.
  53          */
  54         if (file->f_flags & O_SYNC)
  55                 return 1;
  56         return !( test_bit(X86_FEATURE_MTRR, boot_cpu_data.x86_capability) ||
  57                   test_bit(X86_FEATURE_K6_MTRR, boot_cpu_data.x86_capability) ||
  58                   test_bit(X86_FEATURE_CYRIX_ARR, boot_cpu_data.x86_capability) ||
  59                   test_bit(X86_FEATURE_CENTAUR_MCR, boot_cpu_data.x86_capability) )
  60           && addr >= __pa(high_memory);
  61 #elif defined(__x86_64__)
  62         /*
  63          * This is broken because it can generate memory type aliases,
  64          * which can cause cache corruptions
  65          * But it is only available for root and we have to be bug-to-bug
  66          * compatible with i386.
  67          */
  68         if (file->f_flags & O_SYNC)
  69                 return 1;
  70         /* same behaviour as i386. PAT always set to cached and MTRRs control the
  71            caching behaviour.
  72            Hopefully a full PAT implementation will fix that soon. */
  73         return 0;
  74 #elif defined(CONFIG_IA64)
  75         /*
  76          * On ia64, we ignore O_SYNC because we cannot tolerate memory attribute aliases.
  77          */
  78         return !(efi_mem_attributes(addr) & EFI_MEMORY_WB);
  79 #elif defined(CONFIG_PPC64)
  80         /* On PPC64, we always do non-cacheable access to the IO hole and
  81          * cacheable elsewhere. Cache paradox can checkstop the CPU and
  82          * the high_memory heuristic below is wrong on machines with memory
  83          * above the IO hole... Ah, and of course, XFree86 doesn't pass
  84          * O_SYNC when mapping us to tap IO space. Surprised ?
  85          */
  86         return !page_is_ram(addr >> PAGE_SHIFT);
  87 #else
  88         /*
  89          * Accessing memory above the top the kernel knows about or through a file pointer
  90          * that was marked O_SYNC will be done non-cached.
  91          */
  92         if (file->f_flags & O_SYNC)
  93                 return 1;
  94         return addr >= __pa(high_memory);
  95 #endif
  96 }
  97
  98 #ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE
  99 static inline int valid_phys_addr_range(unsigned long addr, size_t *count)
 100 {
 101         unsigned long end_mem;
 102
 103         end_mem = __pa(high_memory);
 104         if (addr >= end_mem)
 105                 return 0;
 106
 107         if (*count > end_mem - addr)
 108                 *count = end_mem - addr;
 109
 110         return 1;
 111 }
 112 #endif
 113
 114 static ssize_t do_write_mem(void *p, unsigned long realp,
 115                             const char __user * buf, size_t count, loff_t *ppos)
 116 {
 117         ssize_t written;
 118         unsigned long copied;
 119
 120         written = 0;
 121 #if defined(__sparc__) || (defined(__mc68000__) && defined(CONFIG_MMU))
 122         /* we don't have page 0 mapped on sparc and m68k.. */
 123         if (realp < PAGE_SIZE) {
 124                 unsigned long sz = PAGE_SIZE-realp;
 125                 if (sz > count) sz = count;
 126                 /* Hmm. Do something? */
 127                 buf+=sz;
 128                 p+=sz;
 129                 count-=sz;
 130                 written+=sz;
 131         }
 132 #endif
 133         copied = copy_from_user(p, buf, count);
 134         if (copied) {
 135                 ssize_t ret = written + (count - copied);
 136
 137                 if (ret)
 138                         return ret;
 139                 return -EFAULT;
 140         }
 141         written += count;
 142         *ppos += written;
 143         return written;
 144 }
 145
 146
 147 /*
 148  * This funcion reads the *physical* memory. The f_pos points directly to the
 149  * memory location.
 150  */
 151 static ssize_t read_mem(struct file * file, char __user * buf,
 152                         size_t count, loff_t *ppos)
 153 {
 154         unsigned long p = *ppos;
 155         ssize_t read;
 156
 157         if (!valid_phys_addr_range(p, &count))
 158                 return -EFAULT;
 159         read = 0;
 160 #if defined(__sparc__) || (defined(__mc68000__) && defined(CONFIG_MMU))
 161         /* we don't have page 0 mapped on sparc and m68k.. */
 162         if (p < PAGE_SIZE) {
 163                 unsigned long sz = PAGE_SIZE-p;
 164                 if (sz > count)
 165                         sz = count;
 166                 if (sz > 0) {
 167                         if (clear_user(buf, sz))
 168                                 return -EFAULT;
 169                         buf += sz;
 170                         p += sz;
 171                         count -= sz;
 172                         read += sz;
 173                 }
 174         }
 175 #endif
 176         if (copy_to_user(buf, __va(p), count))
 177                 return -EFAULT;
 178         read += count;
 179         *ppos += read;
 180         return read;
 181 }
 182
 183 static ssize_t write_mem(struct file * file, const char __user * buf,
 184                          size_t count, loff_t *ppos)
 185 {
 186         unsigned long p = *ppos;
 187
 188         if (!valid_phys_addr_range(p, &count))
 189                 return -EFAULT;
 190         return do_write_mem(__va(p), p, buf, count, ppos);
 191 }
 192
 193 static int mmap_mem(struct file * file, struct vm_area_struct * vma)
 194 {
 195 #ifdef pgprot_noncached
 196         unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
 197         int uncached;
 198
 199         uncached = uncached_access(file, offset);
 200         if (uncached)
 201                 vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 202 #endif
 203
 204         /* Remap-pfn-range will mark the range VM_IO and VM_RESERVED */
 205         if (remap_pfn_range(vma,
 206                             vma->vm_start,
 207                             vma->vm_pgoff,
 208                             vma->vm_end-vma->vm_start,
 209                             vma->vm_page_prot))
 210                 return -EAGAIN;
 211         return 0;
 212 }
 213
 214 extern long vread(char *buf, char *addr, unsigned long count);
 215 extern long vwrite(char *buf, char *addr, unsigned long count);
 216
 217 /*
 218  * This function reads the *virtual* memory as seen by the kernel.
 219  */
 220 static ssize_t read_kmem(struct file *file, char __user *buf,
 221                          size_t count, loff_t *ppos)
 222 {
 223         unsigned long p = *ppos;
 224         ssize_t read = 0;
 225         ssize_t virtr = 0;
 226         char * kbuf; /* k-addr because vread() takes vmlist_lock rwlock */
 227
 228         if (p < (unsigned long) high_memory) {
 229                 read = count;
 230                 if (count > (unsigned long) high_memory - p)
 231                         read = (unsigned long) high_memory - p;
 232
 233 #if defined(__sparc__) || (defined(__mc68000__) && defined(CONFIG_MMU))
 234                 /* we don't have page 0 mapped on sparc and m68k.. */
 235                 if (p < PAGE_SIZE && read > 0) {
 236                         size_t tmp = PAGE_SIZE - p;
 237                         if (tmp > read) tmp = read;
 238                         if (clear_user(buf, tmp))
 239                                 return -EFAULT;
 240                         buf += tmp;
 241                         p += tmp;
 242                         read -= tmp;
 243                         count -= tmp;
 244                 }
 245 #endif
 246                 if (copy_to_user(buf, (char *)p, read))
 247                         return -EFAULT;
 248                 p += read;
 249                 buf += read;
 250                 count -= read;
 251         }
 252
 253         if (count > 0) {
 254                 kbuf = (char *)__get_free_page(GFP_KERNEL);
 255                 if (!kbuf)
 256                         return -ENOMEM;
 257                 while (count > 0) {
 258                         int len = count;
 259
 260                         if (len > PAGE_SIZE)
 261                                 len = PAGE_SIZE;
 262                         len = vread(kbuf, (char *)p, len);
 263                         if (!len)
 264                                 break;
 265                         if (copy_to_user(buf, kbuf, len)) {
 266                                 free_page((unsigned long)kbuf);
 267                                 return -EFAULT;
 268                         }
 269                         count -= len;
 270                         buf += len;
 271                         virtr += len;
 272                         p += len;
 273                 }
 274                 free_page((unsigned long)kbuf);
 275         }
 276         *ppos = p;
 277         return virtr + read;
 278 }
 279
 280 /*
 281  * This function writes to the *virtual* memory as seen by the kernel.
 282  */
 283 static ssize_t write_kmem(struct file * file, const char __user * buf,
 284                           size_t count, loff_t *ppos)
 285 {
 286         unsigned long p = *ppos;
 287         ssize_t wrote = 0;
 288         ssize_t virtr = 0;
 289         ssize_t written;
 290         char * kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
 291
 292         if (p < (unsigned long) high_memory) {
 293
 294                 wrote = count;
 295                 if (count > (unsigned long) high_memory - p)
 296                         wrote = (unsigned long) high_memory - p;
 297
 298                 written = do_write_mem((void*)p, p, buf, wrote, ppos);
 299                 if (written != wrote)
 300                         return written;
 301                 wrote = written;
 302                 p += wrote;
 303                 buf += wrote;
 304                 count -= wrote;
 305         }
 306
 307         if (count > 0) {
 308                 kbuf = (char *)__get_free_page(GFP_KERNEL);
 309                 if (!kbuf)
 310                         return wrote ? wrote : -ENOMEM;
 311                 while (count > 0) {
 312                         int len = count;
 313
 314                         if (len > PAGE_SIZE)
 315                                 len = PAGE_SIZE;
 316                         if (len) {
 317                                 written = copy_from_user(kbuf, buf, len);
 318                                 if (written) {
 319                                         ssize_t ret;
 320
 321                                         free_page((unsigned long)kbuf);
 322                                         ret = wrote + virtr + (len - written);
 323                                         return ret ? ret : -EFAULT;
 324                                 }
 325                         }
 326                         len = vwrite(kbuf, (char *)p, len);
 327                         count -= len;
 328                         buf += len;
 329                         virtr += len;
 330                         p += len;
 331                 }
 332                 free_page((unsigned long)kbuf);
 333         }
 334
 335         *ppos = p;
 336         return virtr + wrote;
 337 }
 338
 339 #if defined(CONFIG_ISA) || !defined(__mc68000__)
 340 static ssize_t read_port(struct file * file, char __user * buf,
 341                          size_t count, loff_t *ppos)
 342 {
 343         unsigned long i = *ppos;
 344         char __user *tmp = buf;
 345
 346         if (verify_area(VERIFY_WRITE,buf,count))
 347                 return -EFAULT;
 348         while (count-- > 0 && i < 65536) {
 349                 if (__put_user(inb(i),tmp) < 0)
 350                         return -EFAULT;
 351                 i++;
 352                 tmp++;
 353         }
 354         *ppos = i;
 355         return tmp-buf;
 356 }
 357
 358 static ssize_t write_port(struct file * file, const char __user * buf,
 359                           size_t count, loff_t *ppos)
 360 {
 361         unsigned long i = *ppos;
 362         const char __user * tmp = buf;
 363
 364         if (verify_area(VERIFY_READ,buf,count))
 365                 return -EFAULT;
 366         while (count-- > 0 && i < 65536) {
 367                 char c;
 368                 if (__get_user(c, tmp))
 369                         return -EFAULT;
 370                 outb(c,i);
 371                 i++;
 372                 tmp++;
 373         }
 374         *ppos = i;
 375         return tmp-buf;
 376 }
 377 #endif
 378
 379 static ssize_t read_null(struct file * file, char __user * buf,
 380                          size_t count, loff_t *ppos)
 381 {
 382         return 0;
 383 }
 384
 385 static ssize_t write_null(struct file * file, const char __user * buf,
 386                           size_t count, loff_t *ppos)
 387 {
 388         return count;
 389 }
 390
 391 #ifdef CONFIG_MMU
 392 /*
 393  * For fun, we are using the MMU for this.
 394  */
 395 static inline size_t read_zero_pagealigned(char __user * buf, size_t size)
 396 {
 397         struct mm_struct *mm;
 398         struct vm_area_struct * vma;
 399         unsigned long addr=(unsigned long)buf;
 400
 401         mm = current->mm;
 402         /* Oops, this was forgotten before. -ben */
 403         down_read(&mm->mmap_sem);
 404
 405         /* For private mappings, just map in zero pages. */
 406         for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) {
 407                 unsigned long count;
 408
 409                 if (vma->vm_start > addr || (vma->vm_flags & VM_WRITE) == 0)
 410                         goto out_up;
 411                 if (vma->vm_flags & (VM_SHARED | VM_HUGETLB))
 412                         break;
 413                 count = vma->vm_end - addr;
 414                 if (count > size)
 415                         count = size;
 416
 417                 zap_page_range(vma, addr, count, NULL);
 418                 zeromap_page_range(vma, addr, count, PAGE_COPY);
 419
 420                 size -= count;
 421                 buf += count;
 422                 addr += count;
 423                 if (size == 0)
 424                         goto out_up;
 425         }
 426
 427         up_read(&mm->mmap_sem);
 428
 429         /* The shared case is hard. Let's do the conventional zeroing. */
 430         do {
 431                 unsigned long unwritten = clear_user(buf, PAGE_SIZE);
 432                 if (unwritten)
 433                         return size + unwritten - PAGE_SIZE;
 434                 cond_resched();
 435                 buf += PAGE_SIZE;
 436                 size -= PAGE_SIZE;
 437         } while (size);
 438
 439         return size;
 440 out_up:
 441         up_read(&mm->mmap_sem);
 442         return size;
 443 }
 444
 445 static ssize_t read_zero(struct file * file, char __user * buf,
 446                          size_t count, loff_t *ppos)
 447 {
 448         unsigned long left, unwritten, written = 0;
 449
 450         if (!count)
 451                 return 0;
 452
 453         if (!access_ok(VERIFY_WRITE, buf, count))
 454                 return -EFAULT;
 455
 456         left = count;
 457
 458         /* do we want to be clever? Arbitrary cut-off */
 459         if (count >= PAGE_SIZE*4) {
 460                 unsigned long partial;
 461
 462                 /* How much left of the page? */
 463                 partial = (PAGE_SIZE-1) & -(unsigned long) buf;
 464                 unwritten = clear_user(buf, partial);
 465                 written = partial - unwritten;
 466                 if (unwritten)
 467                         goto out;
 468                 left -= partial;
 469                 buf += partial;
 470                 unwritten = read_zero_pagealigned(buf, left & PAGE_MASK);
 471                 written += (left & PAGE_MASK) - unwritten;
 472                 if (unwritten)
 473                         goto out;
 474                 buf += left & PAGE_MASK;
 475                 left &= ~PAGE_MASK;
 476         }
 477         unwritten = clear_user(buf, left);
 478         written += left - unwritten;
 479 out:
 480         return written ? written : -EFAULT;
 481 }
 482
 483 static int mmap_zero(struct file * file, struct vm_area_struct * vma)
 484 {
 485         if (vma->vm_flags & VM_SHARED)
 486                 return shmem_zero_setup(vma);
 487         if (zeromap_page_range(vma, vma->vm_start, vma->vm_end - vma->vm_start, vma->vm_page_prot))
 488                 return -EAGAIN;
 489         return 0;
 490 }
 491 #else /* CONFIG_MMU */
 492 static ssize_t read_zero(struct file * file, char * buf,
 493                          size_t count, loff_t *ppos)
 494 {
 495         size_t todo = count;
 496
 497         while (todo) {
 498                 size_t chunk = todo;
 499
 500                 if (chunk > 4096)
 501                         chunk = 4096;   /* Just for latency reasons */
 502                 if (clear_user(buf, chunk))
 503                         return -EFAULT;
 504                 buf += chunk;
 505                 todo -= chunk;
 506                 cond_resched();
 507         }
 508         return count;
 509 }
 510
 511 static int mmap_zero(struct file * file, struct vm_area_struct * vma)
 512 {
 513         return -ENOSYS;
 514 }
 515 #endif /* CONFIG_MMU */
 516
 517 static ssize_t write_full(struct file * file, const char __user * buf,
 518                           size_t count, loff_t *ppos)
 519 {
 520         return -ENOSPC;
 521 }
 522
 523 /*
 524  * Special lseek() function for /dev/null and /dev/zero.  Most notably, you
 525  * can fopen() both devices with "a" now.  This was previously impossible.
 526  * -- SRB.
 527  */
 528
 529 static loff_t null_lseek(struct file * file, loff_t offset, int orig)
 530 {
 531         return file->f_pos = 0;
 532 }
 533
 534 /*
 535  * The memory devices use the full 32/64 bits of the offset, and so we cannot
 536  * check against negative addresses: they are ok. The return value is weird,
 537  * though, in that case (0).
 538  *
 539  * also note that seeking relative to the "end of file" isn't supported:
 540  * it has no meaning, so it returns -EINVAL.
 541  */
 542 static loff_t memory_lseek(struct file * file, loff_t offset, int orig)
 543 {
 544         loff_t ret;
 545
 546         down(&file->f_dentry->d_inode->i_sem);
 547         switch (orig) {
 548                 case 0:
 549                         file->f_pos = offset;
 550                         ret = file->f_pos;
 551                         force_successful_syscall_return();
 552                         break;
 553                 case 1:
 554                         file->f_pos += offset;
 555                         ret = file->f_pos;
 556                         force_successful_syscall_return();
 557                         break;
 558                 default:
 559                         ret = -EINVAL;
 560         }
 561         up(&file->f_dentry->d_inode->i_sem);
 562         return ret;
 563 }
 564
 565 static int open_port(struct inode * inode, struct file * filp)
 566 {
 567         return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
 568 }
 569
 570 #define mmap_kmem       mmap_mem
 571 #define zero_lseek      null_lseek
 572 #define full_lseek      null_lseek
 573 #define write_zero      write_null
 574 #define read_full       read_zero
 575 #define open_mem        open_port
 576 #define open_kmem       open_mem
 577
 578 static struct file_operations mem_fops = {
 579         .llseek         = memory_lseek,
 580         .read           = read_mem,
 581         .write          = write_mem,
 582         .mmap           = mmap_mem,
 583         .open           = open_mem,
 584 };
 585
 586 static struct file_operations kmem_fops = {
 587         .llseek         = memory_lseek,
 588         .read           = read_kmem,
 589         .write          = write_kmem,
 590         .mmap           = mmap_kmem,
 591         .open           = open_kmem,
 592 };
 593
 594 static struct file_operations null_fops = {
 595         .llseek         = null_lseek,
 596         .read           = read_null,
 597         .write          = write_null,
 598 };
 599
 600 #if defined(CONFIG_ISA) || !defined(__mc68000__)
 601 static struct file_operations port_fops = {
 602         .llseek         = memory_lseek,
 603         .read           = read_port,
 604         .write          = write_port,
 605         .open           = open_port,
 606 };
 607 #endif
 608
 609 static struct file_operations zero_fops = {
 610         .llseek         = zero_lseek,
 611         .read           = read_zero,
 612         .write          = write_zero,
 613         .mmap           = mmap_zero,
 614 };
 615
 616 static struct file_operations full_fops = {
 617         .llseek         = full_lseek,
 618         .read           = read_full,
 619         .write          = write_full,
 620 };
 621
 622 static ssize_t kmsg_write(struct file * file, const char __user * buf,
 623                           size_t count, loff_t *ppos)
 624 {
 625         char *tmp;
 626         int ret;
 627
 628         tmp = kmalloc(count + 1, GFP_KERNEL);
 629         if (tmp == NULL)
 630                 return -ENOMEM;
 631         ret = -EFAULT;
 632         if (!copy_from_user(tmp, buf, count)) {
 633                 tmp[count] = 0;
 634                 ret = printk("%s", tmp);
 635         }
 636         kfree(tmp);
 637         return ret;
 638 }
 639
 640 static struct file_operations kmsg_fops = {
 641         .write =        kmsg_write,
 642 };
 643
 644 static int memory_open(struct inode * inode, struct file * filp)
 645 {
 646         switch (iminor(inode)) {
 647                 case 1:
 648                         filp->f_op = &mem_fops;
 649                         break;
 650                 case 2:
 651                         filp->f_op = &kmem_fops;
 652                         break;
 653                 case 3:
 654                         filp->f_op = &null_fops;
 655                         break;
 656 #if defined(CONFIG_ISA) || !defined(__mc68000__)
 657                 case 4:
 658                         filp->f_op = &port_fops;
 659                         break;
 660 #endif
 661                 case 5:
 662                         filp->f_op = &zero_fops;
 663                         break;
 664                 case 7:
 665                         filp->f_op = &full_fops;
 666                         break;
 667                 case 8:
 668                         filp->f_op = &random_fops;
 669                         break;
 670                 case 9:
 671                         filp->f_op = &urandom_fops;
 672                         break;
 673                 case 11:
 674                         filp->f_op = &kmsg_fops;
 675                         break;
 676                 default:
 677                         return -ENXIO;
 678         }
 679         if (filp->f_op && filp->f_op->open)
 680                 return filp->f_op->open(inode,filp);
 681         return 0;
 682 }
 683
 684 static struct file_operations memory_fops = {
 685         .open           = memory_open,  /* just a selector for the real open */
 686 };
 687
 688 static const struct {
 689         unsigned int            minor;
 690         char                    *name;
 691         umode_t                 mode;
 692         struct file_operations  *fops;
 693 } devlist[] = { /* list of minor devices */
 694         {1, "mem",     S_IRUSR | S_IWUSR | S_IRGRP, &mem_fops},
 695         {2, "kmem",    S_IRUSR | S_IWUSR | S_IRGRP, &kmem_fops},
 696         {3, "null",    S_IRUGO | S_IWUGO,           &null_fops},
 697 #if defined(CONFIG_ISA) || !defined(__mc68000__)
 698         {4, "port",    S_IRUSR | S_IWUSR | S_IRGRP, &port_fops},
 699 #endif
 700         {5, "zero",    S_IRUGO | S_IWUGO,           &zero_fops},
 701         {7, "full",    S_IRUGO | S_IWUGO,           &full_fops},
 702         {8, "random",  S_IRUGO | S_IWUSR,           &random_fops},
 703         {9, "urandom", S_IRUGO | S_IWUSR,           &urandom_fops},
 704         {11,"kmsg",    S_IRUGO | S_IWUSR,           &kmsg_fops},
 705 };
 706
 707 static struct class_simple *mem_class;
 708
 709 static int __init chr_dev_init(void)
 710 {
 711         int i;
 712
 713         if (register_chrdev(MEM_MAJOR,"mem",&memory_fops))
 714                 printk("unable to get major %d for memory devs\n", MEM_MAJOR);
 715
 716         mem_class = class_simple_create(THIS_MODULE, "mem");
 717         for (i = 0; i < ARRAY_SIZE(devlist); i++) {
 718                 class_simple_device_add(mem_class,
 719                                         MKDEV(MEM_MAJOR, devlist[i].minor),
 720                                         NULL, devlist[i].name);
 721                 devfs_mk_cdev(MKDEV(MEM_MAJOR, devlist[i].minor),
 722                                 S_IFCHR | devlist[i].mode, devlist[i].name);
 723         }
 724
 725         return 0;
 726 }
 727
 728 fs_initcall(chr_dev_init);